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Stangarm J, Mintara R, Jumpato W, Gomontean B, Thanee I, Wongpakam K, Adler PH, Saijuntha W, Pramual P. Molecular detection of blood protozoa and identification of black flies of the Simulium varicorne species group (Diptera: Simuliidae) in Thailand. Acta Trop 2024; 254:107207. [PMID: 38579961 DOI: 10.1016/j.actatropica.2024.107207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 03/19/2024] [Accepted: 04/02/2024] [Indexed: 04/07/2024]
Abstract
Species of the Simulium varicorne group in Thailand have veterinary significance as vectors of haemosporidian parasites. Accurate identification is, therefore, critical to the study of vectors and parasites. We used morphology and molecular markers to investigate cryptic genetic lineages in samples identified as Simulium chumpornense Takaoka & Kuvangkadilok, 2000. We also tested the efficiency of the nuclear internal transcribed spacer 2 (ITS2) marker for the identification of species in this group. Morphological examinations revealed that S. chumpornense lineage A is most similar to S. khelangense Takaoka, Srisuka & Saeung, 2022, with minor morphological differences. They are also genetically similar based on mitochondrial cytochrome c oxidase I (COI) sequences. Geographically, the sampling site where paratypes of S. khelangense were originally collected is <50 km from where S. chumpornense lineage A was collected. We concluded that cryptic lineage A of S. chumpornense is actually S. khelangense. COI sequences could not differentiate S. kuvangkadilokae Pramual and Tangkawanit, 2008 from S. chumpornense and S. khelangense. In contrast, ITS2 sequences provided perfect accuracy in the identification of these species. Molecular analyses of the blood protozoa Leucocytozoon and Trypanosoma demonstrated that S. khelangense carries L. shoutedeni, Leucocytozoon sp., and Trypanosoma avium. The Leucocytozoon sp. in S. khelangense differs genetically from that in S. asakoae Takaoka & Davies, 1995, signaling the possibility of vector-parasite specificity.
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Affiliation(s)
- Jiraporn Stangarm
- Division of Basic and Medical Sciences, Faculty of Allied Health Sciences, Pathumthani University, Pathum Thani 12000, Thailand
| | - Ronnalit Mintara
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand
| | - Waraporn Jumpato
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand
| | - Bhuvadol Gomontean
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand
| | - Isara Thanee
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand
| | - Komgrit Wongpakam
- Walai Rukhavej Botanical Research Institute, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand
| | - Peter H Adler
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC 29634-0310, USA
| | - Weerachai Saijuntha
- Faculty of Medicine, Mahasarakham University, Maha Sarakham 44000, Thailand; Center of Excellence in Biodiversity Research, Mahasarakham University, Maha Sarakham 44150, Thailand
| | - Pairot Pramual
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand; Center of Excellence in Biodiversity Research, Mahasarakham University, Maha Sarakham 44150, Thailand.
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Doherty M, Grant JR, Pilotte N, Bennuru S, Fischer K, Fischer PU, Lustigman S, Nutman TB, Pfarr K, Hoerauf A, Unnasch TR, Hassan HK, Wanji S, Lammie PJ, Ottesen E, Mackenzie C, Williams SA. Optimized strategy for real-time qPCR detection of Onchocerca volvulus DNA in pooled Simulium sp. blackfly vectors. PLoS Negl Trop Dis 2023; 17:e0011815. [PMID: 38096317 PMCID: PMC10754622 DOI: 10.1371/journal.pntd.0011815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 12/28/2023] [Accepted: 11/22/2023] [Indexed: 12/30/2023] Open
Abstract
BACKGROUND Onchocerca volvulus is a filarial parasite that is a major cause of dermatitis and blindness in endemic regions primarily in sub-Saharan Africa. Widespread efforts to control the disease caused by O. volvulus infection (onchocerciasis) began in 1974 and in recent years, following successful elimination of transmission in much of the Americas, the focus of efforts in Africa has moved from control to the more challenging goal of elimination of transmission in all endemic countries. Mass drug administration (MDA) with ivermectin has reached more than 150 million people and elimination of transmission has been confirmed in four South American countries, with at least two African countries having now stopped MDA as they approach verification of elimination. It is essential that accurate data for active transmission are used to assist in making the critical decision to stop MDA, since missing low levels of transmission and infection can lead to continued spread or recrudescence of the disease. METHODOLOGY/PRINCIPAL FINDINGS Current World Health Organization guidelines for MDA stopping decisions and post-treatment surveillance include screening pools of the Simulium blackfly vector for the presence of O. volvulus larvae using a PCR-ELISA-based molecular technique. In this study, we address the potential of an updated, practical, standardized molecular diagnostic tool with increased sensitivity and species-specificity by comparing several candidate qPCR assays. When paired with heat-stable reagents, a qPCR assay with a mitochondrial DNA target (OvND5) was found to be more sensitive and species-specific than an O150 qPCR, which targets a non-protein coding repetitive DNA sequence. The OvND5 assay detected 19/20 pools of 100 blackfly heads spiked with a single L3, compared to 16/20 for the O150 qPCR assay. CONCLUSIONS/SIGNIFICANCE Given the improved sensitivity, species-specificity and resistance to PCR inhibitors, we identified OvND5 as the optimal target for field sample detection. All reagents for this assay can be shipped at room temperature with no loss of activity. The qPCR protocol we propose is also simpler, faster, and more cost-effective than the current end-point molecular assays.
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Affiliation(s)
- Mary Doherty
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
| | - Jessica R. Grant
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
| | - Nils Pilotte
- Department of Biological Sciences, Quinnipiac University, Hamden, Connecticut, United States of America
| | - Sasisekhar Bennuru
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Kerstin Fischer
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Peter U. Fischer
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Sara Lustigman
- Laboratory of Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
| | - Thomas B. Nutman
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Kenneth Pfarr
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- German Center for Infection Research (DZIF), Partner-Site Bonn-Cologne, Bonn, Germany
| | - Achim Hoerauf
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- German Center for Infection Research (DZIF), Partner-Site Bonn-Cologne, Bonn, Germany
| | - Thomas R. Unnasch
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida, United States of America
| | - Hassan K. Hassan
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida, United States of America
| | - Samuel Wanji
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment, Buea, Cameroon
| | - Patrick J. Lammie
- NTD-SC, Task Force for Global Health, Atlanta, Georgia, United States of America
| | - Eric Ottesen
- NTD-SC, Task Force for Global Health, Atlanta, Georgia, United States of America
| | - Charles Mackenzie
- NTD-SC, Task Force for Global Health, Atlanta, Georgia, United States of America
- RLMF, The END Fund, New York, New York, United States of America
| | - Steven A. Williams
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
- Molecular and Cellular Biology Program, University of Massachusetts, Amherst, Massachusetts, United States of America
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Lourdes EY, Ya'cob Z, Low VL, Izwan-Anas N, Mansor MS, Dawood MM, Takaoka H, Adler PH. Natural infections and distributions of parasitic mermithids (Nematoda: Mermithidae) infecting larval black flies (Diptera: Simuliidae) in tropical streams of Malaysia. Acta Trop 2022; 230:106386. [PMID: 35248580 DOI: 10.1016/j.actatropica.2022.106386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 11/18/2022]
Abstract
Mermithids are parasites of black flies that cause host mortality along with physical and behavioural changes in infected hosts. However, there is a lack of knowledge on the distribution of mermithids infecting black fly larvae and the factors that influence these distributions in Asia, including Malaysia. A total of 13,116 mid- to late-instar black fly larvae belonging to 42 species were collected from 138 streams across East and West Malaysia and screened for the presence of mermithid parasites. Overall, 121 mermithids were obtained from 107 (0.82%) larvae of nine (21.4%) black fly species. The average number of mermithids per black fly host was 1.10 ± 0.04 (SE), ranging from one to three mermithids per host. Mermithid infection was highest in Simulium trangense, with a frequency of occurrence of 6.5%, followed by S. cheongi (5.8%) and S. angulistylum complex (2.9%). Infection was lowest in S. brevipar and S. tahanense, with a frequency of occurrence of 0.7% each. Regression analysis indicated that mermithid infections in larval black flies were significantly associated with cooler and shallower streams with more canopy cover, dense riparian vegetation, high dissolved oxygen, and lower conductivity and complete pH. Forward logistic regression further indicated that infections in S. cheongi were associated with shaded, cooler, slightly acidic streams with higher conductivity and dissolved oxygen. These findings suggest that mermithid infections in larval black flies in Malaysia are not randomly distributed and are influenced by the breeding habitat of their hosts.
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Affiliation(s)
- Emmanuel Y Lourdes
- Higher Institution Centre of Excellence, Tropical Infectious Diseases Research and Education Centre (TIDREC), Universiti Malaya, 50603, Kuala Lumpur, Malaysia
| | - Zubaidah Ya'cob
- Higher Institution Centre of Excellence, Tropical Infectious Diseases Research and Education Centre (TIDREC), Universiti Malaya, 50603, Kuala Lumpur, Malaysia.
| | - Van Lun Low
- Higher Institution Centre of Excellence, Tropical Infectious Diseases Research and Education Centre (TIDREC), Universiti Malaya, 50603, Kuala Lumpur, Malaysia
| | - Noor Izwan-Anas
- Higher Institution Centre of Excellence, Tropical Infectious Diseases Research and Education Centre (TIDREC), Universiti Malaya, 50603, Kuala Lumpur, Malaysia
| | - Mohd Saiful Mansor
- Department of Biological Sciences and Biotechnology Faculty of Science and Technology Universiti Kebangsaan Malaysia (UKM) 43600, Selangor, Malaysia
| | - Mahadimenakbar M Dawood
- Institute for Tropical Biology and Conservation (ITBC), University of Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia
| | - Hiroyuki Takaoka
- Higher Institution Centre of Excellence, Tropical Infectious Diseases Research and Education Centre (TIDREC), Universiti Malaya, 50603, Kuala Lumpur, Malaysia
| | - Peter H Adler
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC 29634-0310, USA
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Johanns SI, Gantin RG, Wangala B, Komlan K, Halatoko WA, Banla M, Karabou P, Luty AJF, Schulz-Key H, Köhler C, Soboslay PT. Onchocerca volvulus-specific antibody and cellular responses in onchocerciasis patients treated annually with ivermectin for 30 years and exposed to parasite transmission in central Togo. PLoS Negl Trop Dis 2022; 16:e0010340. [PMID: 35503786 PMCID: PMC9064110 DOI: 10.1371/journal.pntd.0010340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 03/20/2022] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Annual mass drug administrations (MDA) of ivermectin will strongly reduce Onchocerca volvulus microfilariae (mf) in the skin and in the onchocerciasis patients' eyes. Ivermectin treatment will also affect the expression of immunity in patients, such that activated immune defenses may help control and contribute to clearance of mf of O. volvulus. Longitudinal surveys are a prerequisite to determining the impact of ivermectin on the status of anti-parasite immunity, notably in risk zones where parasite transmission and active O. volvulus infections persist. METHODOLOGY/PRINCIPAL FINDINGS Onchocerciasis patients were treated annually with ivermectin and their Onchocerca volvulus antigen (OvAg) specific IgG and cellular responses were investigated before and at 30 years post initial ivermectin treatment (30yPT). Repeated annual ivermectin treatments eliminated persisting O. volvulus microfilariae (mf) from the skin of patients and abrogated patent infections. The OvAg-specific IgG1 and IgG4 responses were diminished at 30yPT to the levels observed in endemic controls. Prior to starting ivermectin treatment, OvAg-induced cellular productions of IL-10, IFN-γ, CCL13, CCL17 and CCL18 were low in patients, and at 30yPT, cellular cytokine and chemokine responses increased to the levels observed in endemic controls. In contrast, mitogen(PHA)- induced IL-10, IFN-γ, CCL17 and CCL18 cellular production was diminished. This divergent response profile thus revealed increased parasite antigen-specific but reduced polyclonal cellular responsiveness in patients. The transmission of O. volvulus continued at the patients' location in the Mô river basin in central Togo 2018 and 2019 when 0.58% and 0.45%, respectively, of Simulium damnosum s.l. vector blackflies carried O. volvulus infections. CONCLUSIONS/SIGNIFICANCE Repeated annual ivermectin treatment of onchocerciasis patients durably inhibited their patent O. volvulus infections despite ongoing low-level parasite transmission in the study area. Repeated MDA with ivermectin affects the expression of immunity in patients. O. volvulus parasite-specific antibody levels diminished to levels seen in infection-free endemic controls. With low antibody levels, antibody-dependent cellular cytotoxic responses against tissue-dwelling O. volvulus larvae will weaken. O. volvulus antigen inducible cytokine and chemokine production increased in treated mf-negative patients, while their innate responsiveness to mitogen declined. Such lower innate responsiveness in elderly patients could contribute to reduced adaptive immune responses to parasite infections and vaccines. On the other hand, increased specific cellular chemokine responses in mf-negative onchocerciasis patients could reflect effector cell activation against tissue invasive larval stages of O. volvulus. The annual Simulium damnosum s.l. biting rate observed in the Mô river basin was similar to levels prior to initiation of MDA with ivermectin, and the positive rtPCR results reported here confirm ongoing O. volvulus transmission.
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Affiliation(s)
- Saskia I. Johanns
- University Clinics Tübingen, Institute for Tropical Medicine, Eberhard-Karls University, Tübingen, Germany
| | - Richard G. Gantin
- Onchocerciasis Reference Laboratory, Institut National d’Hygiene, Centre Hospitalier Regional, Sokode, Togo
| | - Bawoubadi Wangala
- Onchocerciasis Reference Laboratory, Institut National d’Hygiene, Centre Hospitalier Regional, Sokode, Togo
| | | | | | - Meba Banla
- Centre Hospitalier Universitaire, Université de Lomé, Lomé, Togo
| | | | - Adrian JF Luty
- Université de Paris, Institut de Recherche pour le Développement, Paris, France
| | - Hartwig Schulz-Key
- University Clinics Tübingen, Institute for Tropical Medicine, Eberhard-Karls University, Tübingen, Germany
| | - Carsten Köhler
- University Clinics Tübingen, Institute for Tropical Medicine, Eberhard-Karls University, Tübingen, Germany
| | - Peter T. Soboslay
- University Clinics Tübingen, Institute for Tropical Medicine, Eberhard-Karls University, Tübingen, Germany
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Pramual P, Jomkumsing P, Wathasith P, Wongpakam K. Population structure and population history of the black fly Simulium chumpornense (Diptera: Simuliidae) from Thailand. Acta Trop 2022; 227:106301. [PMID: 34986384 DOI: 10.1016/j.actatropica.2021.106301] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 11/30/2022]
Abstract
Understanding genetic structure and diversity of insect vectors is crucial for disease epidemiology. In this study, mitochondrial cytochrome c oxidase I sequences were used to infer genetic diversity, genetic structure and population history of the black fly, Simulium chumpornense Takaoka and Kuvangkadilok, a suspected vector of blood protozoa of the genus Leucocytozoon and Trypanosoma. High intraspecific genetic divergence (max. 3.76%) was found among 142 specimens obtained from 19 locations across Thailand. A median joining network revealed two genetic lineages (A and B) that were geographically associated. Lineage A is representative of central and northeastern regions. Lineage B represents specimens from diverse locations in northern, western, and southern Thailand, including the type locality. Mismatch distribution and the neutrality tests provided signals of past population expansions in both lineages. The expansion time dating back to the end of last glaciations at 12,000 - 15,000 years ago is possibly related to increasing of precipitation at the end of last glacial period. Despite recent population history, population pairwise FST analysis revealed that almost all population comparisons were genetically significantly different. The high level of genetic structuring is possibly a result of historical isolation of the population that survived in different refugia sites during the dry conditions during glaciations.
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Affiliation(s)
- Pairot Pramual
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham, 44150, Thailand.
| | - Panya Jomkumsing
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham, 44150, Thailand
| | - Pornthida Wathasith
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham, 44150, Thailand
| | - Komgrit Wongpakam
- Walai Rukhavej Botanical Research Institute, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150 Thailand
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Silva TRRD, Narzetti LHDA, Crainey JL, Costa CH, Santos YVSD, Leles LFDO, Pessoa FAC, Vicente ACP, Luz SLB. Molecular detection of Mansonella mariae incriminates Simulium oyapockense as a potentially important bridge vector for Amazon-region zoonoses. Infect Genet Evol 2022; 98:105200. [PMID: 34990852 DOI: 10.1016/j.meegid.2021.105200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 12/27/2021] [Accepted: 12/28/2021] [Indexed: 06/14/2023]
Abstract
OBJECTIVE To assess the emergent zoonotic disease risk posed by the voracious human-biting blackfly species Simulium oyapockense in the peripheral regions of an expanding urban centre situated deep in the Brazilian Amazon rainforest. METHODS We performed nine human landing catches at three periurban sites surrounding the Brazilian Amazon town of São Gabriel da Cachoeira. Using the detection of non-human primate filarial parasites as an indicator of the zoonotic disease threat posed by a biting insect, we screened 3328 S. oyapockense blackflies for the presence of zoonotic filarial DNA with an ITS-1 PCR assay and Sanger sequencing. RESULTS Between 98 and 100% of the biting insects captured during our nine collections were identified as S. oyapockense; at our three collection sites and during our three seasonally-distinct collections this species was captured at rates between 28 and 294 blackflies per hour. PCR screening of the march-collected S. oyapockense detected infectious-stage (L3) Mansonella mariae parasites (which are only known to infect non-human primates) in >0.15% of the tested head samples. CONCLUSIONS Our results show that residents of the periurban regions of São Gabriel da Cachoeira are routinely exposed to the bites of S. oyapockense blackflies which have previously fed on non-human primates.
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Affiliation(s)
- Túllio Romão Ribeiro da Silva
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil; Programa de Pós-graduação Stricto Sensu em Biologia Parasitária, Instituto Oswaldo Cruz/IOC/FIOCRUZ, Rio de Janeiro, RJ, Brazil
| | - Luiz Henrique de Aquino Narzetti
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil; Programa Institucional de Bolsas de Iniciação Científica (PIBIC), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil
| | - James Lee Crainey
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil.
| | - Carlos Henrique Costa
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil; Programa de Pós-graduação Stricto sensu em Biologia Computacional e Sistemas do Instituto Oswaldo Cruz (PGBCS/IOC/Fiocruz), Brazil
| | - Yago Vinícius Serra Dos Santos
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil; Programa de Pós-Graduação Stricto Sensu em Biologia da Interação Patógeno Hospedeiro (PPGBIO-Interação), Instituto Leônidas e Maria Deane/ ILMD/Fiocruz Amazônia, Manaus, AM, Brazil
| | - Lorena Ferreira de Oliveira Leles
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil; Programa de Pós-Graduação Stricto Sensu em Biologia da Interação Patógeno Hospedeiro (PPGBIO-Interação), Instituto Leônidas e Maria Deane/ ILMD/Fiocruz Amazônia, Manaus, AM, Brazil
| | - Felipe Arley Costa Pessoa
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil
| | - Ana Carolina Paulo Vicente
- Instituto Oswaldo Cruz/IOC/FIOCRUZ, Laboratório de Genética Molecular de Microrganismos, Rio de Janeiro, RJ, Brazil
| | - Sérgio Luiz Bessa Luz
- Instituto Leônidas e Maria Deane/ILMD/Fiocruz Amazônia, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brazil
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Willen L, Milton P, Hamley JID, Walker M, Osei-Atweneboana MY, Volf P, Basáñez MG, Courtenay O. Demographic patterns of human antibody levels to Simulium damnosum s.l. saliva in onchocerciasis-endemic areas: An indicator of exposure to vector bites. PLoS Negl Trop Dis 2022; 16:e0010108. [PMID: 35020729 PMCID: PMC8789114 DOI: 10.1371/journal.pntd.0010108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 01/25/2022] [Accepted: 12/17/2021] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In onchocerciasis endemic areas in Africa, heterogenous biting rates by blackfly vectors on humans are assumed to partially explain age- and sex-dependent infection patterns with Onchocerca volvulus. To underpin these assumptions and further improve predictions made by onchocerciasis transmission models, demographic patterns in antibody responses to salivary antigens of Simulium damnosum s.l. are evaluated as a measure of blackfly exposure. METHODOLOGY/PRINCIPAL FINDINGS Recently developed IgG and IgM anti-saliva immunoassays for S. damnosum s.l. were applied to blood samples collected from residents in four onchocerciasis endemic villages in Ghana. Demographic patterns in antibody levels according to village, sex and age were explored by fitting generalized linear models. Antibody levels varied between villages but showed consistent patterns with age and sex. Both IgG and IgM responses declined with increasing age. IgG responses were generally lower in males than in females and exhibited a steeper decline in adult males than in adult females. No sex-specific difference was observed in IgM responses. CONCLUSIONS/SIGNIFICANCE The decline in age-specific antibody patterns suggested development of immunotolerance or desensitization to blackfly saliva antigen in response to persistent exposure. The variation between sexes, and between adults and youngsters may reflect differences in behaviour influencing cumulative exposure. These measures of antibody acquisition and decay could be incorporated into onchocerciasis transmission models towards informing onchocerciasis control, elimination, and surveillance.
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Affiliation(s)
- Laura Willen
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic
- Centre for the Evaluation of Vaccinations, Vaccine and Infectious Disease Institute, University of Antwerp, Wilrijk, Belgium
- * E-mail: (LW); (OC)
| | - Philip Milton
- MRC Centre for Global Infectious Disease Analysis and London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom
| | - Jonathan I. D. Hamley
- MRC Centre for Global Infectious Disease Analysis and London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom
| | - Martin Walker
- London Centre for Neglected Tropical Disease Research and Department of Pathobiology and Population Sciences, Royal Veterinary College, Hatfield, United Kingdom
| | | | - Petr Volf
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Maria-Gloria Basáñez
- MRC Centre for Global Infectious Disease Analysis and London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom
| | - Orin Courtenay
- Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research and School of Life Sciences, University of Warwick, Coventry, United Kingdom
- * E-mail: (LW); (OC)
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Chakarov N, Veiga J, Ruiz-Arrondo I, Valera F. Atypical behavior of a black fly species connects cavity-nesting birds with generalist blood parasites in an arid area of Spain. Parasit Vectors 2021; 14:298. [PMID: 34082829 PMCID: PMC8173925 DOI: 10.1186/s13071-021-04798-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 05/20/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND The feeding behavior of bloodsucking insects determines the transmission, distribution, host spectrum and evolution of blood parasites in the wild. Conventional wisdom suggests that some vector groups (e.g. black flies, family Simuliidae) are consistently exophagous daytime biters. We aimed to understand more about the exceptions to this pattern by combining targeted trapping and molecular identification of parasites in vectors. METHODS In this study, we collected black flies in nest boxes used by European rollers Coracias garrulus in southeastern Spain. We molecularly analyzed 434 individual insects, identifying the black fly species caught in the nest boxes, their potential vertebrate blood meals, and the haemosporidian parasite lineages that they carried. RESULTS Only one black fly species, Simulium rubzovianum, appeared to enter the nest boxes of rollers. Among the trapped specimens, 15% contained vertebrate DNA, which always belonged to rollers, even though only half of those specimens were visibly engorged. Furthermore, 15% of all black flies contained Leucocytozoon lineages, indicating previous feeding on avian hosts but probably not on infected adult rollers. The known vertebrate hosts of the recorded Leucocytozoon lineages suggested that large and/or abundant birds are their hosts. Particularly represented were cavity-nesting species breeding in the vicinity, such as pigeons, corvids and owls. Open-nesting species such as thrushes and birds of prey were also represented. CONCLUSIONS Our data strongly suggest that S. rubzovianum bites uninfected roller nestlings and infected individuals of other species, potentially incubating adults, inside nest boxes and natural cavities. This simuliid does not appear to have a strong preference for specific host clades. Contrary to the general pattern for the group, and possibly enhanced by the harsh environmental conditions in the study area, this black fly appeared to intensively use and may even have a preference for confined spaces such as cavities for feeding and resting. Preferences of vectors for atypical microhabitat niches where hosts are less mobile may enable social and within-family transmission and parasite speciation in the long term. At the same time, a lack of host preference in concentrated multispecies communities can lead to host switches. Both processes may be underappreciated driving forces in the evolution of avian blood parasites.
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Affiliation(s)
- Nayden Chakarov
- Department of Animal Behaviour, Bielefeld University, Bielefeld, Germany
| | - Jesús Veiga
- Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (EEZA-CSIC), Almería, Spain
| | - Ignacio Ruiz-Arrondo
- Centre for Rickettsiosis and Arthropod-Borne Diseases, Hospital Universitario San Pedro-CIBIR, Logroño, Spain
| | - Francisco Valera
- Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (EEZA-CSIC), Almería, Spain
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9
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de Vos AS, Stolk WA, Coffeng LE, de Vlas SJ. The impact of mass drug administration expansion to low onchocerciasis prevalence settings in case of connected villages. PLoS Negl Trop Dis 2021; 15:e0009011. [PMID: 33979331 PMCID: PMC8143415 DOI: 10.1371/journal.pntd.0009011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 05/24/2021] [Accepted: 04/26/2021] [Indexed: 11/21/2022] Open
Abstract
Background The existence of locations with low but stable onchocerciasis prevalence is not well understood. An often suggested yet poorly investigated explanation is that the infection spills over from neighbouring locations with higher infection densities. Methodology We adapted the stochastic individual based model ONCHOSIM to enable the simulation of multiple villages, with separate blackfly (intermediate host) and human populations, which are connected through the regular movement of the villagers and/or the flies. With this model we explore the impact of the type, direction and degree of connectedness, and of the impact of localized or full-area mass drug administration (MDA) over a range of connected village settings. Principal findings In settings with annual fly biting rates (ABR) below the threshold needed for stable local transmission, persistence of onchocerciasis prevalence can well be explained by regular human traffic and/or fly movement from locations with higher ABR. Elimination of onchocerciasis will then theoretically be reached by only implementing MDA in the higher prevalence area, although lingering infection in the low prevalence location can trigger resurgence of transmission in the total region when MDA is stopped too soon. Expanding MDA implementation to the lower ABR location can therefore shorten the duration of MDA needed. For example, when prevalence spill-over is due to human traffic, and both locations have about equal populations, then the MDA duration can be shortened by up to three years. If the lower ABR location has twice as many inhabitants, the reduction can even be up to six years, but if spill-over is due to fly movement, the expected reduction is less than a year. Conclusions/Significance Although MDA implementation might not always be necessary in locations with stable low onchocerciasis prevalence, in many circumstances it is recommended to accelerate achieving elimination in the wider area. When infected by onchocerciasis worm parasites, people can eventually develop blindness or severe skin morbidity. Over the past decades, in most places with high onchocerciasis prevalence, annual mass drug administration has become freely available for all inhabitants, regardless of their infection status. This policy has been highly successful in decreasing morbidity. For the next aim, to eliminate onchocerciasis, this intervention is now being expanded to lower prevalence locations. We have adapted an existing simulation model of the spread of onchocerciasis to allow us to model settings where multiple villages are connected, through movement of either humans or blackflies, the intermediate host. By this connection, worms could spill over from a high prevalence village to neighbouring villages with lower prevalence. For such situations, we have examined the impact of implementing treatment only in the high prevalence village, or also in one or two lower prevalence villages. We conclude that for elimination of onchocerciasis transmission, treatment in the lower prevalence villages may not actually be needed, but the total duration of mass drug administration in the entire area can be significantly decreased by expanding treatment to these villages.
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Affiliation(s)
- Anneke S. de Vos
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
- * E-mail:
| | - Wilma A. Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Luc E. Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Sake J. de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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10
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Abong RA, Amambo GN, Hamid AA, Enow BA, Beng AA, Nietcho FN, Nji TM, Njouendou AJ, Ritter M, Esum ME, Deribe K, Cho JF, Fombad FF, Enyong PI, Poole C, Pfarr K, Hoerauf A, Carlow C, Wanji S. The Mbam drainage system and onchocerciasis transmission post ivermectin mass drug administration (MDA) campaign, Cameroon. PLoS Negl Trop Dis 2021; 15:e0008926. [PMID: 33465080 PMCID: PMC7815102 DOI: 10.1371/journal.pntd.0008926] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Accepted: 10/27/2020] [Indexed: 11/19/2022] Open
Abstract
Background The impact of large scale Mass Drug Adminstration (MDA) of ivermectin on active onchocerciasis transmission by Simulium damnosum, which transmits the parasite O. volvulus is of great importance for onchocerciasis control programmes. We investigated in the Mbam river system area, the impact of MDA of ivermectin on entomological indices and also verify if there are river system factors that could have favoured the transmission of onchocerciasis in this area and contribute to the persistence of disease. We compared three independent techniques to detect Onchocerca larvae in blackflies and also analyzed the river system within 9 months post-MDA of ivermectin. Method Simulium flies were captured before and after 1, 3, 6 and 9months of ivermectin-MDA. The biting rate was determined and 41% of the flies dissected while the rest were grouped into pools of 100 flies for DNA extraction. The extracted DNA was then subjected to O-150 LAMP and real-time PCR for the detection of infection by Onchocerca species using pool screening. The river system was analysed and the water discharge compared between rainy and dry seasons. Principal findings We used human landing collection method (previously called human bait) to collect 22,274 adult female Simulium flies from Mbam River System. Of this number, 9,134 were dissected while 129 pools constituted for molecular screening. Overall biting and parous rates of 1113 flies/man/day and 24.7%, respectively, were observed. All diagnostic techniques detected similar rates of O. volvulus infection (P = 0.9252) and infectivity (P = 0.4825) at all monitoring time points. Onchocerca ochengi larvae were only detected in 2 of the 129 pools. Analysis of the river drainage revealed two hydroelectric dams constructed on the tributaries of the Mbam river were the key contributing factor to the high-water discharge during both rainy and dry seasons. Conclusion Results from fly dissection (Microscopy), real-time PCR and LAMP revealed the same trends pre- and post-MDA. The infection rate with animal Onchocerca sp was exceptionally low. The dense river system generate important breeding sites that govern the abundance of Simulium during both dry and rainy seasons. The presence of parasite strains that respond sub-optimally to an approved drug, favourable breeding sites for the vector and infected individual in an area, will surely provide conditions for continuous and persistent transmission of a disease despite a long-term control intervention. We investigated the impact of ivermectin on entomological indices within 9 months following a large-scale MDA in the Mbam river drainage. The river system factors that could have favoured abundance vector breeding and contribute to the persistence of disease transmission were also examined within the study period. We observed vector abundance and high entomological indices throughout the study period following ivermectin MDA. We also observed high water discharge along the main river of the drainage basin in both the rainy and dry seasons and this is due to the presence of two dams constructed upstream at Bamendjing and Mape to regularize the course of river Sanaga in view of generating hydroelectric power at Edea. Factors favouring continuous and persistent disease transmission are present in this drainage basin despite over 20 years of annual IVM-MDA. There is need for alternative control strategy in order to accelerate the fight against onchocerciasis in the area.
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Affiliation(s)
- Raphael Awah Abong
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Glory Ngongeh Amambo
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Ali Ahamat Hamid
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Belinda Agbor Enow
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Amuam Andrew Beng
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Franck Noel Nietcho
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Theobald Mue Nji
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
- Department of Sociology and Anthropology, University of Buea, Cameroon
| | - Abdel Jelil Njouendou
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Department of Biomedical science, Faculty of Health Sciences, University of Buea, Buea, Cameroon
| | - Manuel Ritter
- Institute for Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | - Mathias Eyong Esum
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Kebede Deribe
- Global Health and Infection Department, Brighton and Sussex Medical School, Brighton, United Kingdom
- School of Public Health, Addis Ababa University, Addis Ababa, Ethiopia
| | - Jerome Fru Cho
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Fanny Fri Fombad
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Peter Ivo Enyong
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
| | - Catherine Poole
- New England Biolabs, Ipswich, Massachusetts, United States of America
| | - Kenneth Pfarr
- Institute for Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- German Center for Infection Research (DZIF), partner site Bonn-Cologne, Bonn, Germany
| | - Achim Hoerauf
- Institute for Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- German Center for Infection Research (DZIF), partner site Bonn-Cologne, Bonn, Germany
| | - Clotilde Carlow
- New England Biolabs, Ipswich, Massachusetts, United States of America
| | - Samuel Wanji
- Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon
- * E-mail:
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11
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McCreadie JW, Adler PH. The general architecture of black fly-parasite interactions: Parasitism in lotic systems at a continental scale. J Invertebr Pathol 2020; 178:107518. [PMID: 33333064 DOI: 10.1016/j.jip.2020.107518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 12/08/2020] [Accepted: 12/09/2020] [Indexed: 11/19/2022]
Abstract
We examined the general architecture of interactions between stream-dwelling larval black flies (Diptera: Simuliidae) and their common parasites in 1736 collections across North America. Mermithid nematodes (family Mermithidae), microsporidia (phylum Microsporidia), and the fungus Coelomycidium simulii Debaisieux (phylum Blastocladiomycota) infected larval black flies. We found similar continental distributions for these three parasite taxa across North America. At least one of these taxa was represented in 42.2% of all black fly collections. Species interactions in ecological networks typically imply that each link between species is equally important. By employing quantitative measures of host susceptibilities and parasite dependencies, we provide a more complete structure for host-parasite networks. The distribution of parasite dependencies and host susceptibilities were right-skewed, with low values indicating that most dependencies (parasites) and susceptibilities (hosts) were weak. Although regression analysis between host frequency and parasite incidence were highly significant, frequency analysis suggested that the distributions of parasites differ significantly among the four most common and closely related (same subgenus) species of hosts. A highly significant pattern of nestedness in our bipartite host-parasite network indicated that specialized parasites (i.e., those that interact with few host species) tend to occur as subsets of the most common hosts.
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Affiliation(s)
- John W McCreadie
- Department of Biological Sciences, University of South Alabama, Mobile, AL, USA.
| | - Peter H Adler
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, USA.
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12
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Oforka LC, Adeleke MA, Anikwe JC, Hardy NB, Mathias DK, Makanjuola WA, Fadamiro HY. Biting Rates and Onchocerca Infectivity Status of Black Flies from the Simulium damnosum Complex (Diptera: Simuliidae) in Osun State, Nigeria. J Med Entomol 2020; 57:901-907. [PMID: 31901168 DOI: 10.1093/jme/tjz250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Indexed: 06/10/2023]
Abstract
The Simulium damnosum Theobald complex transmits Onchocerca volvulus Leuckart (Spirurida: Onchocercidae), the causative agent of onchocerciasis. Recent evidence suggests that control efforts have strongly suppressed parasite populations, but vector surveillance is needed in parts of Africa where the disease remains endemic. Here, studies on biting rates and infectivity status of suspected vector species were conducted in three onchocerciasis-endemic areas, namely Iwo, Ede, and Obokun, in Osun State, Nigeria. A total of 3,035 black flies were collected between October 2014 and September 2016, and examined for parity and parasites using standard methods. A separate collection of 2,000 black flies was pool-screened for infectivity using polymerase chain reaction (PCR) amplification of the O-150 marker. Results showed that parous flies were significantly less common than nulliparous flies with overall parous rates of 8.02% in Iwo and 35.38% in Ede at the end of the study period. Obokun had a parous rate of 22.22% obtained in the first year only. None of the dissected parous flies were infected with O. volvulus and PCR assays showed no amplification of O-150 O. volvulus-specific repeats in head and body pools. However, annual biting rates exceeded the World Health Organization threshold of 1,000 bites/person/yr. Thus it appears that, with such high rates of biting, even low levels of vector infection can sustain onchocerciasis in African communities.
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Affiliation(s)
- Linda C Oforka
- Department of Zoology, University of Lagos, Akoka, Yaba, 101017, Lagos, Nigeria
| | - Monsuru A Adeleke
- Department of Zoology, Osun State University, P.M.B 4494, Osogbo, Nigeria
| | - Joseph C Anikwe
- Department of Zoology, University of Lagos, Akoka, Yaba, 101017, Lagos, Nigeria
| | - Nate B Hardy
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL
| | - Derrick K Mathias
- Florida Medical Entomology Laboratory, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL
| | | | - Henry Y Fadamiro
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL
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13
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Saeung A, Srisuka W, Aupalee K, Fukuda M, Otsuka Y, Taai K, Maleewong W, Takaoka H. Natural infections with larvae of Onchocerca species type I in the human-biting black fly, Simulium nigrogilvum (Diptera: Simuliidae), in western Thailand. Acta Trop 2020; 204:105344. [PMID: 31954685 DOI: 10.1016/j.actatropica.2020.105344] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/14/2020] [Accepted: 01/14/2020] [Indexed: 02/06/2023]
Abstract
Zoonotic onchocerciasis is a human infection caused by Onchocerca species of animal origins and transmitted by black fly vectors. The reported incidence of this disease has increased throughout the world. This study aims to clarify the vectorial roles of black fly species in zoonotic filarial transmission in Tak province, western Thailand. The integrated approach of morphological and DNA sequence-based analyses was used to identify species of both wild-caught female black flies and infective filarial larvae found in the infected black flies. All of 494 female black flies captured were identified as Simulium nigrogilvum, through scanning electron microscopy (SEM) and DNA sequence analyses based on the cytochrome c oxidase subunit I (COI) and subunit II (COII), and the fast-evolving nuclear elongation complex protein 1 (ECP1) genes. Four females of S. nigrogilvum harbored one to three third-stage larvae (infective larvae) in their thoraces, with an infection rate of 0.81% (4/494). All infective larvae were similar in morphology and size to one another, being identified as Onchocerca species type I (= O. sp. type A), a bovine filaria, originally reported from Japan, and also as O. sp. found in S. nodosum in Thailand, based on their body lengths and widths being 1,068-1,346 µm long by 25-28 µm wide, and morphological characters. Comparisons of cytochrome c oxidase subunit I (COI) and 12S rRNA sequences of mitochondrial DNA (mtDNA) and phylogenetic analyses with those of previous reports strongly supported that all larvae were O. sp. type I. This report is the first indicating the presence of O. sp. type I in Thailand and its vector being S. nigrogilvum.
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Affiliation(s)
- Atiporn Saeung
- Center of Insect Vector Study, Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Wichai Srisuka
- Entomology Section, Queen Sirikit Botanic Garden, P.O. Box 7, Chiang Mai 50180, Thailand
| | - Kittipat Aupalee
- Center of Insect Vector Study, Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Masako Fukuda
- Institute for Research Promotion, Oita University, Idaigaoka 1-1, Hasama, Yufu City, Oita 879-5593, Japan.
| | - Yasushi Otsuka
- Research Center for the Pacific Islands, Kagoshima University, Korimoto 1-21-24, Kagoshima City, Kagoshima 890-8580, Japan.
| | - Kritsana Taai
- Faculty of Veterinary Medicine, Western University, Kanchanaburi 71170, Thailand
| | - Wanchai Maleewong
- Department of Parasitology, Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
| | - Hiroyuki Takaoka
- Tropical Infectious Diseases Research and Education Centre (TIDREC), University of Malaya, 50603, Kuala Lumpur, Malaysia.
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14
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Onah IE, Ubachukwu PO, Eyo JE. Status of Onchocerca volvulus infection and transmission by blackflies after 15 years of ivermectin distribution at Adani, Nigeria. Trop Biomed 2020; 37:174-185. [PMID: 33612728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The nuisance bites of blackflies and transmission of Onchocerca volvulus, which causes onchocerciasis, constitutes a threat to public health and an impediment to food production in rural and riverine communities in Nigeria. The entomological profile of onchocerciasis at Adani, Nigeria, was investigated from August 2010 to January 2011 to determine the transmission of O. volvulus after 15 years of ivermectin distribution in the area. A total of 548 adult female blackflies of the Simulium damnosum complex were caught using human baits and dissected. Of this number, 248 flies were caught in the wet season (August to October), while 300 flies were caught in the dry season (November to January). The relative abundance of flies at Adani varied from 21 in December to 243 in January. The monthly catches between September and October and between December and January were significantly different. The monthly population density of the flies ranged from 0.5Flies/Man/Hour (FMH) in December to 5.5FMH in January. The diurnal biting pattern of the S. damnosum complex at the site showed a bimodal peak of activity with the evening peak being higher than the morning peak except in October when the morning peak was higher than the evening peak. The morning peaks were observed between 7.00 am and 10.00 am, whereas the evening peaks occurred between 4.00 pm and 6.00 pm. The morning and evening biting peaks in all the months were not significantly different. Nulliparous flies accounted for 75.7% of the total catch, whereas 24.3% of the flies caught were parous. The infection, infective bites and transmission of O. volvulus during the study period were zero. This study suggests that transmission of O. volvulus has been halted and the flies are presently more nuisance biters than disease vectors since no stage of O. volvulus was found in the flies dissected.
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Affiliation(s)
- I E Onah
- Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Enugu State, Nigeria
| | - P O Ubachukwu
- Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Enugu State, Nigeria
| | - J E Eyo
- Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Enugu State, Nigeria
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15
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Katabarwa MN, Zarroug IMA, Negussu N, Aziz NM, Tadesse Z, Elmubark WA, Shumo Z, Meribo K, Kamal H, Mohammed A, Bitew Y, Seid T, Bekele F, Yilak A, Endeshaw T, Hassen M, Tillahun A, Samuel F, Birhanu H, Asmare T, Boakye D, Feleke SM, Unnasch T, Post R, Higazi T, Griswold E, Mackenzie C, Richards F. The Galabat-Metema cross-border onchocerciasis focus: The first coordinated interruption of onchocerciasis transmission in Africa. PLoS Negl Trop Dis 2020; 14:e0007830. [PMID: 32027648 PMCID: PMC7004312 DOI: 10.1371/journal.pntd.0007830] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 10/05/2019] [Indexed: 11/18/2022] Open
Abstract
Background Onchocerciasis transmission across international borders is not uncommon, yet a coordinated cross border stops mass drug administration (MDA) decision has not been documented. Methods/Principle findings The Galabat-Metema focus involves neighboring districts on the border between Sudan and Ethiopia. Mass drug administration (MDA) was provided once and subsequently twice per year in this focus, with twice-per-year beginning in Ethiopia’s Metema subfocus in 2016 and in the Sudan’s Galabat subfocus in 2008. Ov16 ELISA-based serosurveys were conducted in 6072 children under 10 years of age in the Metema subfocus in 2014, and 3931 in the Galabat in 2015. Between 2014 and 2016, a total of 27,583 vector Simulium damnosum flies from Metema and 9,148 flies from Galabat were tested by pool screen PCR for Onchocerca volvulus O-150 DNA. Only 8 children were Ov16 seropositive (all in the Metema subfocus); all were negative by skin snip PCR. The upper limit of the 95% confidence interval (UCL) for Ov16 seropositive was <0.1% for the overall focus and 0.14 positive fly heads per 2000 (UCL = 0.39/2000). However, an entomological ‘hotspot’ was detected on the Wudi Gemzu river in Metema district. The hotspot was confirmed when 4 more positive fly pools were found on repeat testing in 2017 (1.04 L3/2000 flies (UCL = 2.26/2000). Information exchange between the two countries led to stopping MDA in a coordinated fashion in 2018, with the exception of the hotspot at Wudi Gemzu, where MDA with ivermectin was increased to every three months to hasten interruption of transmission. Conclusion Coordinated stop MDA decisions were made by Sudan and Ethiopia based on data satisfying the World Health Organization’s criteria for interruption of onchocerciasis transmission. Definitions of entomological ‘hotspots’ and buffer zones around the focus are proposed. Onchocerciasis is a vector-borne tropical disease caused by the parasitc worm, Onchocerca volvulus. The vector is Simulium flies that breed in fast flowing rivers and streams. The infection can cause skin disease and loss of vision, giving risk to the common name of ‘river blindness’ for the condition. Ivermectin (Mectizan) mass drug administration (MDA) given at high coverage for many years can interrupt transmission such that MDA can eventually be stopped. The present paper provides highlights of onchocerciasis transmission interruption in the first known coordinated international cross border focus with ivermectin MDA program in Africa, where 99% of the global onchocerciasis burden exists. This focus known as Galabat-Metema is shared between Ethiopia and Sudan, both of which have established a nationwide policy for elimination of onchocerciasis. The paper provides the history of MDA in the border area and the results leading a coordinated end to MDA in the focus in 2017.
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Affiliation(s)
- Moses N. Katabarwa
- Health Programs, The Carter Center, Atlanta, Georgia, United States of America
- * E-mail:
| | | | | | | | | | | | | | - Kadu Meribo
- Federal Ministry of Health, Addis Ababa, Ethiopia
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Thomas Unnasch
- College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Rory Post
- London School of Hygiene & Tropical Medicine, London, United Kingdom, United Kingdom
| | - Tarig Higazi
- Department of Biological Sciences, Ohio University, Zanesville, Ohio, United States of America
| | - Emily Griswold
- Health Programs, The Carter Center, Atlanta, Georgia, United States of America
| | - Charles Mackenzie
- NTD Support Center, Task Force for Global Health, Atlanta, Georgia, United States of America
| | - Frank Richards
- Health Programs, The Carter Center, Atlanta, Georgia, United States of America
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16
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Pramual P, Bunchom N, Saijuntha W, Tada I, Suganuma N, Agatsuma T. Genetic diversity and DNA barcoding of the black fly (Diptera: Simuliidae) vectors of parasites causing human onchocerciasis in Guatemala. Trop Biomed 2019; 36:938-957. [PMID: 33597465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Genetic variation based on mitochondrial cytochrome c oxidase I (COI) and II (COII) sequences was investigated for three black fly nominal species, Simulium metallicum Bellardi complex, S. callidum Dyar and Shannon, and S. ochraceum Walker complex, which are vectors of human onchocerciasis from Guatemala. High levels of genetic diversity were found in S. metallicum complex and S. ochraceum complex with maximum intraspecific genetic divergences of 11.39% and 4.25%, respectively. Levels of genetic diversity of these nominal species are consistent with species status for both of them as they are cytologically complexes of species. Phylogenetic analyses revealed that the S. metallicum complex from Guatemala divided into three distinct clades, two with members of this species from several Central and South American countries and another exclusively from Mexico. The Simulium ochraceum complex from Guatemala formed a clade with members of this species from Mexico and Costa Rica while those from Ecuador and Colombia formed another distinct clade. Very low diversity in S. callidum was found for both genes with maximum intraspecific genetic divergence of 0.68% for COI and 0.88% for COII. Low genetic diversity in S. callidum might be a consequence of the result being informative of only recent population history of the species.
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Affiliation(s)
- P Pramual
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham, 44150, Thailand
| | - N Bunchom
- Walai Rukhavej Botanical Research Institute (WRBRI), Mahasarakham University, Kantharawichai District, Maha Sarakham, 44150, Thailand
| | - W Saijuntha
- Walai Rukhavej Botanical Research Institute (WRBRI), Mahasarakham University, Kantharawichai District, Maha Sarakham, 44150, Thailand
| | - I Tada
- Eijuen Elderly Care Institution, Kyushu, Japan
| | - N Suganuma
- Department of Environmental Medicine, Kochi Medical School, Kochi University, Oko, Nankoku, 783-8505, Japan
| | - T Agatsuma
- Department of Environmental Medicine, Kochi Medical School, Kochi University, Oko, Nankoku, 783-8505, Japan
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Thaijarern J, Tangkawanit U, Wongpakam K, Pramual P. Molecular detection of Trypanosoma (Kinetoplastida: Trypanosomatidae) in black flies (Diptera: Simuliidae) from Thailand. Acta Trop 2019; 200:105196. [PMID: 31545950 DOI: 10.1016/j.actatropica.2019.105196] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 09/19/2019] [Accepted: 09/19/2019] [Indexed: 01/01/2023]
Abstract
Trypanosomes are parasitic flagellate protozoans that are important disease causing agents in humans and animals including economically significant livestock. Many blood-sucking insects are known to be vectors of trypanosomes but there is no data for the haematophagous black fly species in Asia. In this study, a molecular approach based on the small subunit ribosomal RNA (SSU rRNA) gene was used to detect trypanosomes in black flies from Thailand. A total of 470 wild-caught adult black flies representing nine morphological species were examined. Ten (2%) specimens of two ornithophilic black fly species, Simulium asakoae complex (n = 4) and S. chumpornense (n = 6), were positive for trypanosomes. The SSU rRNA sequences revealed that all trypanosome DNA found in black flies from Thailand is closely related to Trypanosoma avium with >99% sequence similarity. This is also supported by a phylogenetic analysis in which all trypanosomes from Thai black flies were resolved in the clade of T. avium. This is the first report for trypanosomes in Asian black flies and it is suspected that these insects are potential vectors of avian Trypanosoma.
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Affiliation(s)
- Jiraporn Thaijarern
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand
| | - Ubon Tangkawanit
- Department of Entomology and Plant Pathology, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002 Thailand
| | - Komgrit Wongpakam
- Walai Rukhavej Botanical Research Institute, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150 Thailand
| | - Pairot Pramual
- Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, Thailand.
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Loum D, Cozart D, Lakwo T, Habomugisha P, Jacob B, Cupp EW, Unnasch TR. Optimization and evaluation of the Esperanza Window Trap to reduce biting rates of Simulium damnosum sensu lato in Northern Uganda. PLoS Negl Trop Dis 2019; 13:e0007558. [PMID: 31310607 PMCID: PMC6634373 DOI: 10.1371/journal.pntd.0007558] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 06/18/2019] [Indexed: 11/29/2022] Open
Abstract
Background Onchocerciasis, or river blindness, has historically been an important cause of blindness, skin disease and economic disruption in Africa and the Americas. It is caused by the filarial parasite Onchocerca volvulus, which is transmitted by black flies in the genus Simulium. Over the past decade, several international programs have been formed to control, or more recently eliminate onchocerciasis, using mass drug administration (MDA) of ivermectin. However, in many areas of Africa (particularly those which are endemic for the eyeworm, Loa loa, or where vector densities are very high) ivermectin MDA alone will not be sufficient to achieve elimination. In these situations, additional interventions may be necessary. Methodology/Principal findings The Esperanza Window trap (EWT), a simple trap originally developed to replace human landing collections for entomological surveillance of O. volvulus transmission was optimized, resulting in a 17-fold improvement in trap performance. The optimized trap was tested in trials in schools and in agricultural fields to determine if it could reduce vector biting locally. The traps resulted in a 90% reduction in biting in the school setting. In the field setting, results varied. In one location, the traps reduced biting by roughly 50%, while in a separate trial, the traps did not significantly reduce the biting rate. Examination of the two settings suggested that trap placement may be critical to their success. Conclusions/Significance These results suggest that the optimized EWT might be capable of reducing local vector black fly biting in areas commonly frequented by residents. Together with other recently developed methods of community directed vector control, the traps may augment ivermectin MDA, bringing the goal of onchocerciasis elimination within reach in much of Africa. Onchocerciasis or river blindness is historically one of the most important causes of blindness and skin disease in the developing world. It is caused by infection with the filarial parasite Onchocerca volvulus. The finding that ivermectin was an effective and safe treatment for onchocerciasis and the decision by its manufacturer to donate it to treat this infection spawned the development of programs to eliminate river blindness through mass drug administration of ivermectin to the afflicted populations. This has dramatically reduced the prevalence of onchocerciasis worldwide and has resulted in its near elimination in the Americas. But ivermectin alone will not eliminate river blindness in much of Africa; additional interventions are necessary. Here we report the optimization of a simple trap for the black fly vector of O. volvulus and show that these traps can dramatically reduce vector biting in some settings. Together with other recently developed community directed methods of vector control, these traps may augment the effect of the ivermectin distribution programs, bringing the goal of elimination within reach in much of Africa.
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Affiliation(s)
- Denis Loum
- Nwoya District Local Government, Nwoya, Uganda
| | - Devon Cozart
- Center for Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Thomson Lakwo
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | - Benjamin Jacob
- Center for Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Eddie W. Cupp
- Center for Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Thomas R. Unnasch
- Center for Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
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Romão Ribeiro da Silva T, Crainey JL, Costa Pessoa FA, Vinícius Serra dos Santos Y, Pereira-Silva JW, Ferreira de Oliveira Leles L, Vicente AC, Bessa Luz SL. Blackflies in the ointment: O. volvulus vector biting can be significantly reduced by the skin-application of mineral oil during human landing catches. PLoS Negl Trop Dis 2019; 13:e0007234. [PMID: 30933979 PMCID: PMC6459560 DOI: 10.1371/journal.pntd.0007234] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 04/11/2019] [Accepted: 02/11/2019] [Indexed: 12/02/2022] Open
Abstract
Background Standard human landing catches (sHLCs) have historically been a key component of Onchocerca volvulus transmission monitoring, but expose health-workers to potentially hazardous vector bites. Novel human-bait-free trapping methods have been developed, but do not always work where they are needed and may not generate O. volvulus surveillance data that is directly comparable with historic data. Methodology Simuliid sHLCs and mineral-oil protected HLCs (mopHLCs) were performed in a rural village of Amazonas state, Brazil. A four-hour direct comparisons of sHLCs and mopHLCs was carried-out using six vector collectors, each of whom used one leg for a sHLC and one for a mopHLC. Two-person collection teams then exclusively performed either mopHLCs or sHLCs for a further set of 12 four-hour collections. Following the completion of all collections, simuliid-bite mark estimates were made from legs used exclusively in sHLCs and legs used exclusively in mopHLCs. Principal findings All of the 1669 captured simuliids were identified as the O. volvulus vector Simulium oyapockense. Overall, mopHLC simuliids captured per hour (S/H) rates were lower than those obtained with sHLC trapping (15.5 S/H versus 20 S/H). Direct comparisons of simuliid capture rates found that vector-collectors captured simuliids significantly more efficiently ( x¯: 20.5 S/H) with mopHLC trapping than with sHLC trapping ( x¯: 16.4 S/H): P-value = 0.002. MopHLCs performed in isolation were, however, observed to capture vectors less efficiently ( x¯: 13.4 S/H) than sHLCs performed under similar conditions ( x¯: 19.98 S/H). All six vector collectors had significantly higher simuliid capture per counted bite mark (SC/CBM) rates using mopHLCs than they were observe to have using sHLCs ( x¯: 21 SC/CBM versus x¯: 1 SC/CBM; p-value = 0.03125). Conclusions Vector collectors captured significantly more simuliids per counted bite mark with mopHLCs than with sHLCs. Further investigations into the utility of mopHLCs for onchocerciasis xenomonitoring and beyond are merited. Standard human landing catches (sHLCs) have historically been used to obtain key Onchocerca volvulus transmission data that has helped with the design and monitoring of the WHO´s onchocerciasis control programmes. To avoid the health risks associated with sHLCs, alternative human-bait-free blackfly trapping methods, most of which immobilize and suffocate blackflies with a viscous liquid substance, have been developed. Questions, however, have be raised as to whether these human-bait-free trapping methods generate O. volvulus transmission data that is directly comparable with historic sHLC data. In this study, we have combined sHLCs with mineral oil vector capture and shown that the skin application of mineral oil can significantly reduce (and possibly eliminate) simuliid biting during HLCs. In direct comparisons, we have shown that mineral oil protected human landing catches (mopHLCs) were more efficient at capturing the O. volvulus vector Simulium oyapockense than sHLCs. We have also shown that mopHLCs, performed in isolation of vector collectors using exposed skin for their trapping, are less efficient than HLCs, but still function well. We believe that mopHLCs represent a promising alternative to sHLCs that merit further testing for their utility in the epidemiological monitoring of onchocerciasis and, indeed, other vector borne diseases as well.
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Affiliation(s)
- Túllio Romão Ribeiro da Silva
- Instituto Leônidas e Maria Deane/ILMD/FIOCRUZ, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, 476 Rua Teresina, Adrianópolis, Manaus, Amazonas, Brazil
- Programa de Pós-graduação Stricto sensu em Biologia Parasitária do Instituto Oswaldo Cruz (IOC/Fiocruz), Rio de Janeiro, Brazil
| | - James Lee Crainey
- Instituto Leônidas e Maria Deane/ILMD/FIOCRUZ, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, 476 Rua Teresina, Adrianópolis, Manaus, Amazonas, Brazil
- * E-mail:
| | - Felipe Arley Costa Pessoa
- Instituto Leônidas e Maria Deane/ILMD/FIOCRUZ, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, 476 Rua Teresina, Adrianópolis, Manaus, Amazonas, Brazil
| | - Yago Vinícius Serra dos Santos
- Instituto Leônidas e Maria Deane/ILMD/FIOCRUZ, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, 476 Rua Teresina, Adrianópolis, Manaus, Amazonas, Brazil
- Programa de Pós-Graduação em Biologia da Interação Patógeno Hospedeiro (PPGBIO-Interação), Manaus, Amazonas, Brazil
| | - Jordam William Pereira-Silva
- Instituto Leônidas e Maria Deane/ILMD/FIOCRUZ, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, 476 Rua Teresina, Adrianópolis, Manaus, Amazonas, Brazil
- Programa de Pós-Graduação Stricto Sensu em Condições de Vida e Situações de Saúde na Amazônia (PPGVIDA), Manaus, Amazonas, Brazil
| | - Lorena Ferreira de Oliveira Leles
- Instituto Leônidas e Maria Deane/ILMD/FIOCRUZ, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, 476 Rua Teresina, Adrianópolis, Manaus, Amazonas, Brazil
- Programa de Pós-Graduação em Biologia da Interação Patógeno Hospedeiro (PPGBIO-Interação), Manaus, Amazonas, Brazil
| | - Ana Carolina Vicente
- Instituto Oswaldo Cruz/IOC/FIOCRUZ, Laboratório de Genética Molecular de Microrganismos, Rio de Janeiro, RJ, Brazil
| | - Sérgio Luiz Bessa Luz
- Instituto Leônidas e Maria Deane/ILMD/FIOCRUZ, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, 476 Rua Teresina, Adrianópolis, Manaus, Amazonas, Brazil
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20
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Jacob BG, Loum D, Lakwo TL, Katholi CR, Habomugisha P, Byamukama E, Tukahebwa E, Cupp EW, Unnasch TR. Community-directed vector control to supplement mass drug distribution for onchocerciasis elimination in the Madi mid-North focus of Northern Uganda. PLoS Negl Trop Dis 2018; 12:e0006702. [PMID: 30148838 PMCID: PMC6128654 DOI: 10.1371/journal.pntd.0006702] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/07/2018] [Accepted: 07/19/2018] [Indexed: 11/19/2022] Open
Abstract
Background Onchocerciasis a neglected tropical disease that historically has been a major cause of morbidity and an obstacle to economic development in the developing world. It is caused by infection with Onchocerca volvulus, which is transmitted by black flies of the genus Simulium. The discovery of the potent effect of Mectizan (ivermectin) on O. volvulus microfilariae and the decision by its manufacturer to donate the drug for onchocerciasis spurred the implementation of international programs to control and, more recently, eliminate this scourge. These programs rely primarily on mass distribution of ivermectin (MDA) to the afflicted populations. However, MDA alone will not be sufficient to eliminate onchocerciasis where transmission is intense and where ivermectin MDA is precluded by co-endemicity with Loa loa. Vector control will likely be required as a supplemental intervention in these situations. Methodology/Principal findings Because biting by the black fly vectors is often a major nuisance in onchocerciasis afflicted communities, we hypothesized that community members might be mobilized to clear the breeding sites of the vegetation that represents the primary black fly larvae attachment point. We evaluated the effect of such a community based "slash and clear" intervention in multiple communities in Northern Uganda. Slash and Clear resulted in 89–99% declines in vector biting rates. The effect lasted up to 120 days post intervention. Conclusions/Significance Slash and clear might represent an effective, inexpensive, community- based tool to supplement ivermectin distribution as a contributory method to eliminate onchocerciasis and prevent recrudescence. River blindness is one of the most important causes of morbidity in the developing world. The discovery of ivermectin and the decision by its manufacturer to donate the drug for river blindness spawned the development of programs to eliminate river blindness through mass treatment of afflicted populations. But ivermectin alone will not eliminate river blindness in much of Africa; additional interventions are necessary. We show that a simple community-based approach to controlling the black fly vector results in dramatic reductions in the vector population. Such a community-based approach to vector control will be compatible with the community-driven mass drug administration programs distributing ivermectin for onchocerciasis elimination in Africa. This should help reduce the time needed to obtain elimination and help prevent recrudescence once elimination is attained.
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Affiliation(s)
- Benjamin G. Jacob
- Department of Global Health, College of Public Health, University of South Florida, Tampa, FL United States of America
| | - Denis Loum
- Nwoya District Local Government, Nwoya, Uganda
| | | | - Charles R. Katholi
- Department of Biostatistics, School of Public Health, University of Alabama at Birmingham, Birmingham, AL United States of America
| | | | | | | | - Eddie W. Cupp
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States of America
| | - Thomas R. Unnasch
- Department of Global Health, College of Public Health, University of South Florida, Tampa, FL United States of America
- * E-mail:
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21
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Ledder G, Sylvester D, Bouchat RR, Thiel JA. Continuous and pulsed epidemiological models for onchocerciasis with implications for eradication strategy. Math Biosci Eng 2018; 15:841-862. [PMID: 30380312 DOI: 10.3934/mbe.2018038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Onchocerciasis is an endemic disease in parts of sub-Saharan Africa. Complex mathematical models are being used to assess the likely efficacy of efforts to eradicate the disease; however, their predictions have not always been borne out in practice. In this paper, we represent the immunological aspects of the disease with a single empirical parameter in order to reduce the model complexity. Asymptotic approximation allows us to reduce the vector-borne epidemiological model to a model of an infectious disease with nonlinear incidence. We then consider two versions, one with continuous treatment and a more realistic one where treatment occurs only at intervals. Thorough mathematical analysis of these models yields equilibrium solutions for the continuous case, periodic solutions for the pulsed case, and conditions for the existence of endemic disease equilibria in both cases, thereby leading to simple model criteria for eradication. The analytical results and numerical experiments show that the continuous treatment version is an excellent approximation for the pulsed version and that the current onchocerciasis eradication strategy is inadequate for regions where the incidence is highest and unacceptably slow even when the long-term behavior is the disease-free state.
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Affiliation(s)
- Glenn Ledder
- Department of Mathematics, University of Nebraska-Lincoln, Lincoln, NE 68588-0130, USA
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Verver S, Walker M, Kim YE, Fobi G, Tekle AH, Zouré HGM, Wanji S, Boakye DA, Kuesel AC, de Vlas SJ, Boussinesq M, Basáñez MG, Stolk WA. How Can Onchocerciasis Elimination in Africa Be Accelerated? Modeling the Impact of Increased Ivermectin Treatment Frequency and Complementary Vector Control. Clin Infect Dis 2018; 66:S267-S274. [PMID: 29860291 PMCID: PMC5982715 DOI: 10.1093/cid/cix1137] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Background Great strides have been made toward onchocerciasis elimination by mass drug administration (MDA) of ivermectin. Focusing on MDA-eligible areas, we investigated where the elimination goal can be achieved by 2025 by continuation of current practice (annual MDA with ivermectin) and where intensification or additional vector control is required. We did not consider areas hypoendemic for onchocerciasis with loiasis coendemicity where MDA is contraindicated. Methods We used 2 previously published mathematical models, ONCHOSIM and EPIONCHO, to simulate future trends in microfilarial prevalence for 80 different settings (defined by precontrol endemicity and past MDA frequency and coverage) under different future treatment scenarios (annual, biannual, or quarterly MDA with different treatment coverage through 2025, with or without vector control strategies), assessing for each strategy whether it eventually leads to elimination. Results Areas with 40%-50% precontrol microfilarial prevalence and ≥10 years of annual MDA may achieve elimination with a further 7 years of annual MDA, if not achieved already, according to both models. For most areas with 70%-80% precontrol prevalence, ONCHOSIM predicts that either annual or biannual MDA is sufficient to achieve elimination by 2025, whereas EPIONCHO predicts that elimination will not be achieved even with complementary vector control. Conclusions Whether elimination will be reached by 2025 depends on precontrol endemicity, control history, and strategies chosen from now until 2025. Biannual or quarterly MDA will accelerate progress toward elimination but cannot guarantee it by 2025 in high-endemicity areas. Long-term concomitant MDA and vector control for high-endemicity areas might be useful.
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Affiliation(s)
- Suzanne Verver
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands
| | - Martin Walker
- Department of Pathobiology and Population Sciences and London Centre for Neglected Tropical Disease Research, Royal Veterinary College, Hatfield
- Department of Infectious Disease Epidemiology and London Centre for Neglected Tropical Disease Research, Imperial College London, United Kingdom
| | - Young Eun Kim
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands
- Swiss Tropical and Public Health, Basel, Switzerland
| | - Grace Fobi
- Independent Consultant, Yaoundé, Cameroon
| | | | | | - Samuel Wanji
- Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Cameroon
| | - Daniel A Boakye
- Noguchi Memorial Institute of Medical Research, University of Ghana, Legon
| | - Annette C Kuesel
- United Nations Children’s Fund/United Nations Development Programme/World Bank/World Health Organization Special Programme for Research and Training in Tropical Diseases, Geneva, Switzerland
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands
| | | | - Maria-Gloria Basáñez
- Department of Infectious Disease Epidemiology and London Centre for Neglected Tropical Disease Research, Imperial College London, United Kingdom
| | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands
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Routledge I, Walker M, Cheke RA, Bhatt S, Nkot PB, Matthews GA, Baleguel D, Dobson HM, Wiles TL, Basañez MG. Modelling the impact of larviciding on the population dynamics and biting rates of Simulium damnosum (s.l.): implications for vector control as a complementary strategy for onchocerciasis elimination in Africa. Parasit Vectors 2018; 11:316. [PMID: 29843770 PMCID: PMC5972405 DOI: 10.1186/s13071-018-2864-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 04/23/2018] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND In 2012, the World Health Organization set goals for the elimination of onchocerciasis transmission by 2020 in selected African countries. Epidemiological data and mathematical modelling have indicated that elimination may not be achieved with annual ivermectin distribution in all endemic foci. Complementary and alternative treatment strategies (ATS), including vector control, will be necessary. Implementation of vector control will require that the ecology and population dynamics of Simulium damnosum (sensu lato) be carefully considered. METHODS We adapted our previous SIMuliid POPulation dynamics (SIMPOP) model to explore the impact of larvicidal insecticides on S. damnosum (s.l.) biting rates in different ecological contexts and to identify how frequently and for how long vector control should be continued to sustain substantive reductions in vector biting. SIMPOP was fitted to data from large-scale aerial larviciding trials in savannah sites (Ghana) and small-scale ground larviciding trials in forest areas (Cameroon). The model was validated against independent data from Burkina Faso/Côte d'Ivoire (savannah) and Bioko (forest). Scenario analysis explored the effects of ecological and programmatic factors such as pre-control daily biting rate (DBR) and larviciding scheme design on reductions and resurgences in biting rates. RESULTS The estimated efficacy of large-scale aerial larviciding in the savannah was greater than that of ground-based larviciding in the forest. Small changes in larvicidal efficacy can have large impacts on intervention success. At 93% larvicidal efficacy (a realistic value based on field trials), 10 consecutive weekly larvicidal treatments would reduce DBRs by 96% (e.g. from 400 to 16 bites/person/day). At 70% efficacy, and for 10 weekly applications, the DBR would decrease by 67% (e.g. from 400 to 132 bites/person/day). Larviciding is more likely to succeed in areas with lower water temperatures and where blackfly species have longer gonotrophic cycles. CONCLUSIONS Focal vector control can reduce vector biting rates in settings where a high larvicidal efficacy can be achieved and an appropriate duration and frequency of larviciding can be ensured. Future work linking SIMPOP with onchocerciasis transmission models will permit evaluation of the impact of combined anti-vectorial and anti-parasitic interventions on accelerating elimination of the disease.
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Affiliation(s)
- Isobel Routledge
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s campus), Imperial College London, Norfolk Place, London, W2 1PG UK
| | - Martin Walker
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Pathobiology and Population Sciences, Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA UK
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s campus), Imperial College London, Norfolk Place, London, W2 1PG UK
| | - Robert A. Cheke
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s campus), Imperial College London, Norfolk Place, London, W2 1PG UK
- Natural Resources Institute, Department of Agriculture, Health & Environment, University of Greenwich, Central Avenue, Chatham Maritime, Chatham, Kent, ME4 4TB UK
| | - Samir Bhatt
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s campus), Imperial College London, Norfolk Place, London, W2 1PG UK
| | | | - Graham A. Matthews
- Yaoundé Initiative Foundation, Department of Life Sciences, Faculty of Natural Sciences (Silwood Park), Imperial College London, Ascot, Berkshire SL5 7PY UK
| | - Didier Baleguel
- Yaoundé Initiative Foundation, P.O. Box 3878, Messa, Yaoundé, Cameroon
| | - Hans M. Dobson
- Natural Resources Institute, Department of Agriculture, Health & Environment, University of Greenwich, Central Avenue, Chatham Maritime, Chatham, Kent, ME4 4TB UK
| | - Terry L. Wiles
- Yaoundé Initiative Foundation, P.O. Box 3878, Messa, Yaoundé, Cameroon
- Yaoundé Initiative Foundation, Department of Life Sciences, Faculty of Natural Sciences (Silwood Park), Imperial College London, Ascot, Berkshire SL5 7PY UK
| | - Maria-Gloria Basañez
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s campus), Imperial College London, Norfolk Place, London, W2 1PG UK
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s campus), Imperial College London, Norfolk Place, London, W2 1PG UK
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Herrador Z, Garcia B, Ncogo P, Perteguer MJ, Rubio JM, Rivas E, Cimas M, Ordoñez G, de Pablos S, Hernández-González A, Nguema R, Moya L, Romay-Barja M, Garate T, Barbre K, Benito A. Interruption of onchocerciasis transmission in Bioko Island: Accelerating the movement from control to elimination in Equatorial Guinea. PLoS Negl Trop Dis 2018; 12:e0006471. [PMID: 29723238 PMCID: PMC5953477 DOI: 10.1371/journal.pntd.0006471] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 05/15/2018] [Accepted: 04/22/2018] [Indexed: 11/18/2022] Open
Abstract
Background Onchocerciasis, also known as river blindness, is a parasitic disease. More than 99 percent of all cases occur in Africa. Bioko Island (Equatorial Guinea) is the only island endemic for onchocerciasis in the world. Since 2005, when vector Simulium yahense was eliminated, there have not been any reported cases of infection. This study aimed to demonstrate that updated WHO criteria for stopping mass drug administration (MDA) have been met. Methodology/Principal findings A cross-sectional study was conducted from September 2016 to January 2017. Participants were 5- to 9-year-old school children. Onchocerciasis/lymphatic Filariasis (LF, only in endemic districts) rapid diagnostic tests (RDTs) were performed. Blood spots were collected from RDT positive children and 10 percent of the RDT negatives to determine Ov16 and Wb123 IgG4 antibodies through enzyme-linked immunosorbent assay (ELISA). Skin snips were collected from RDT positives. Filarial detection was performed by PCR in positives and indeterminate sera. Black fly collection was carried out in traditional breeding sites. A total of 7,052 children, ranging from 5 to 9 years of age, were included in the study. Four children (0.06%) were Ov16 IgG4 RDT positives, but negative by ELISA Ov16, while 6 RDT negative children tested positive by ELISA. A total of 1,230 children from the Riaba and Baney districts were tested for LF. One child was Wb123 RDT positive (0.08%), but ELISA negative, while 3 RDT negative children were positive by Wb123 ELISA. All positive samples were negative by PCR for onchocerciasis and LF (in blood spot and skin snip). All fly collections and larval prospections in the traditional catching and prospection sites were negative. Conclusions/Significance WHO criteria have been met, therefore MDA in Bioko Island can be stopped. Three years of post-treatment surveillance should be implemented to identify any new occurrences of exposure or infection. Onchocerciasis, commonly called river blindness, is a chronic parasitic disease particularly prevalent in Africa. It is transmitted through the bites of infected Simulium blackflies. Onchocerciasis is endemic in Equatorial Guinea. Huge achievements have been made in human and vector control during the last two decades, especially on Bioko Island. Eliminating onchocerciasis transmission on Bioko is feasible given its isolation from other landmasses, which also reduces the risk of reinvasion by the disease vector. Recently updated WHO guidelines for stopping mass drug administration (MDA) and verifying elimination of human onchocerciasis (2016) established a new critical threshold to verify elimination of onchocerciasis transmission based on novel serological tests. We applied these techniques in a representative sample of 5- to 9-year-old school children. An entomological assessment was also carried out. We found no evidence of current infection or recent transmission. There was no evidence of onchocerciasis vectors, and our results from the sample population meet the current WHO serologic criteria for stopping MDA. Based on these results, we recommended to the Ministry of Health and Social Welfare of Equatorial Guinea that MDA on Bioko Island be stopped and that 3 years of post-treatment surveillance should be undertaken to identify any new occurrences of exposure or infection.
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Affiliation(s)
- Zaida Herrador
- National Centre for Tropical Medicine, Health Institute Carlos III (ISCIII in Spanish), Madrid, Spain
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
- * E-mail:
| | - Belén Garcia
- National Centre for Tropical Medicine, Health Institute Carlos III (ISCIII in Spanish), Madrid, Spain
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
| | - Policarpo Ncogo
- National Centre for Tropical Medicine, Health Institute Carlos III (ISCIII in Spanish), Madrid, Spain
- Ministry of Health, Malabo, Equatorial Guinea
| | - Maria Jesus Perteguer
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
- National Center of Microbiology, Institute of Health Carlos III, Madrid, Spain
| | - Jose Miguel Rubio
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
- National Center of Microbiology, Institute of Health Carlos III, Madrid, Spain
| | - Eva Rivas
- Department of Preventive Medicine, University Hospital Nuestra Señora de la Candelaria, Tenerife, Spain
| | - Marta Cimas
- National School of Health, Institute of Health Carlos III, Madrid, Spain
| | - Guillermo Ordoñez
- Department of Preventive Medicine, University Hospital of Mostoles, Madrid, Spain
| | - Silvia de Pablos
- National Center of Microbiology, Institute of Health Carlos III, Madrid, Spain
| | - Ana Hernández-González
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
- National Center of Microbiology, Institute of Health Carlos III, Madrid, Spain
| | - Rufino Nguema
- Ministry of Health, Malabo, Equatorial Guinea
- National Program for Onchocerciasis and other Filariasis Control, Ministry of Health, Malabo, Equatorial Guinea
| | - Laura Moya
- Jimenez Diaz Foundation University Hospital, Madrid, Spain
| | - María Romay-Barja
- National Centre for Tropical Medicine, Health Institute Carlos III (ISCIII in Spanish), Madrid, Spain
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
| | - Teresa Garate
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
- National Center of Microbiology, Institute of Health Carlos III, Madrid, Spain
| | - Kira Barbre
- Neglected Tropical Disease Support Center, Task Force for Global Health, Atlanta, Georgia, United States of America
| | - Agustín Benito
- National Centre for Tropical Medicine, Health Institute Carlos III (ISCIII in Spanish), Madrid, Spain
- Network Biomedical Research on Tropical Diseases (RICET in Spanish), Madrid, Spain
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Woodford L, Bianco G, Ivanova Y, Dale M, Elmer K, Rae F, Larcombe SD, Helm B, Ferguson HM, Baldini F. Vector species-specific association between natural Wolbachia infections and avian malaria in black fly populations. Sci Rep 2018; 8:4188. [PMID: 29520067 PMCID: PMC5843599 DOI: 10.1038/s41598-018-22550-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 02/21/2018] [Indexed: 11/08/2022] Open
Abstract
Artificial infection of mosquitoes with the endosymbiont bacteria Wolbachia can interfere with malaria parasite development. Therefore, the release of Wolbachia-infected mosquitoes has been proposed as a malaria control strategy. However, Wolbachia effects on vector competence are only partly understood, as indicated by inconsistent effects on malaria infection reported under laboratory conditions. Studies of naturally-occurring Wolbachia infections in wild vector populations could be useful to identify the ecological and evolutionary conditions under which these endosymbionts can block malaria transmission. Here we demonstrate the occurrence of natural Wolbachia infections in three species of black fly (genus Simulium), which is a main vector of the avian malaria parasite Leucocytozoon. Prevalence of Leucocytozoon was high (25%), but the nature and magnitude of its association with Wolbachia differed between black fly species. Wolbachia infection was positively associated with avian malaria infection in S. cryophilum, negatively associated in S. aureum, and unrelated in S. vernum. These differences suggest that Wolbachia interacts with the parasite in a vector host species-specific manner. This provides a useful model system for further study of how Wolbachia influences vector competence. Such knowledge, including the possibility of undesirable positive association, is required to guide endosymbiont based control methods.
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Affiliation(s)
- Luke Woodford
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
- Department of Biomolecular Sciences, School of Biology, University of St Andrews, St Andrews, United Kingdom
| | - Giovanni Bianco
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Yoana Ivanova
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Maeve Dale
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Kathryn Elmer
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Fiona Rae
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Stephen D Larcombe
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Barbara Helm
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Heather M Ferguson
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Francesco Baldini
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom.
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Mahdy MAK, Abdul-Ghani R, Abdulrahman TAA, Al-Eryani SMA, Al-Mekhlafi AM, Alhaidari SAA, Azazy AA. Onchocerca volvulus infection in Tihama region - west of Yemen: Continuing transmission in ivermectin-targeted endemic foci and unveiled endemicity in districts with previously unknown status. PLoS Negl Trop Dis 2018; 12:e0006329. [PMID: 29505580 PMCID: PMC5854432 DOI: 10.1371/journal.pntd.0006329] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 03/15/2018] [Accepted: 02/20/2018] [Indexed: 11/29/2022] Open
Abstract
Background Onchocerciasis in Yemen is one of the most neglected diseases, where baseline estimates of onchocerciasis and monitoring of the impact of ivermectin regularly administered to the affected individuals on its transmission are lacking. Therefore, this study aimed to determine the anti-Ov16 IgG4 seroprevalence among local communities of Hodeidah and Al-Mahwit governorates of Tihama region. The factors possibly associated with previous exposure to infection were also studied. Methodology/Principal findings This cross-sectional study was conducted in two ivermectin-targeted districts endemic for onchocerciasis in Hodeidah and Al-Mahwit and two untargeted districts with unknown previous endemicity in Hodeidah between February and July 2017. For 508 residents sampled by a multi-stage random approach, data were collected and blood specimens were screened for anti-Ov16 IgG4 using the SD BIOLINE Onchocerciasis IgG4 rapid tests. The study revealed an overall anti-Ov16 IgG4 rate of 18.5% (94/508) in all surveyed districts, with 10.2% (12/118) of children aged ≤10 years being seropositive. Moreover, rates of 8.0% (4/50) and 6.1% (4/66) were found in districts not officially listed as endemic for the disease. Multivariable analysis confirmed the age of more than ten years and residing within a large family as the independent predictors of exposure to infection. Conclusions/Significance Onchocerciasis transmission is still ongoing as supported by the higher anti-Ov16 IgG4 seroprevalence rate among children aged ≤10 years compared to that (<0.1%) previously set by the World Health Organization as a serologic criterion for transmission interruption. Further large-scale studies combining serologic and entomologic criteria are recommended for the mapping of O. volvulus in human and blackfly populations in endemic foci and their neighboring areas of uncertain endemicity. In addition, ivermectin distribution, coverage and impact on disease transmission need to be continually assessed. Onchocerciasis is endemic in certain foci in the western governorates of Yemen. Monitoring the impact of the regular ivermectin administration to affected individuals on the transmission status and providing baseline onchocerciasis estimates in endemic areas are crucial for planning effective elimination strategies. We found that the disease transmission is still ongoing in Hodeidah and Al-Mahwit governorates of Tihama region as indicated by the anti-Ov16 IgG4 seropositivity among children aged ≤10 years. In Bani Sa'ad, where affected individuals had been regularly targeted with ivermectin over the last 15 years, we found that the anti-Ov16 IgG4 seroprevalence rate was significantly lower among children aged ≤10 years (9.1%; 5/55) compared to those >10 years (24.5%; 37/151), reflecting a possible decline in disease transmission. We also revealed onchocerciasis transmission in districts with unknown previous endemicity for the first time, with rates of 8.0% and 6.1% being found in Al Marawi'ah and As Sukhnah districts of Hodeidah. Large-scale surveys are recommended for mapping of O. volvulus in human and blackfly populations in endemic foci and neighboring untargeted areas of uncertain endemicity as a forward step towards the elimination of the disease from the country.
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Affiliation(s)
- Mohammed A. K. Mahdy
- Tropical Disease Research Center, University of Science and Technology, Sana’a, Yemen
- Department of Parasitology, Faculty of Medicine and Health Sciences, Sana’a University, Sana’a, Yemen
- * E-mail:
| | - Rashad Abdul-Ghani
- Tropical Disease Research Center, University of Science and Technology, Sana’a, Yemen
- Department of Parasitology, Faculty of Medicine and Health Sciences, Sana’a University, Sana’a, Yemen
| | | | - Samira M. A. Al-Eryani
- Department of Parasitology, Faculty of Medicine and Health Sciences, Sana’a University, Sana’a, Yemen
| | - Abdulsalam M. Al-Mekhlafi
- Department of Parasitology, Faculty of Medicine and Health Sciences, Sana’a University, Sana’a, Yemen
| | - Sami A. A. Alhaidari
- National Schistosomiasis and Parasites Control Program, Ministry of Public Health and Population, Sana’a, Yemen
| | - Ahmed A. Azazy
- Department of Laboratory Medicine, Faculty of Applied Medical Sciences, Al-Baha University, Al-Baha, KSA
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Boakye D, Tallant J, Adjami A, Moussa S, Tekle A, Robalo M, Rebollo M, Mwinza P, Sitima L, Cantey P, Mackenzie C. Refocusing vector assessment towards the elimination of onchocerciasis from Africa: a review of the current status in selected countries. Int Health 2018; 10:i27-i32. [PMID: 29471346 PMCID: PMC5881273 DOI: 10.1093/inthealth/ihx066] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 11/17/2017] [Accepted: 12/04/2017] [Indexed: 11/29/2022] Open
Abstract
Measures to control onchocerciasis have been in place for well over 30 years. Recently, programs have turned from disease control towards transmission elimination. The absence of infective larvae in the black fly Simulium sp. vector is central to defining elimination, and assessments of infectivity by O150 polymerase chain reaction in the vector not only provide valuable information to programs, but are also required for verification of elimination. The status of transmission in black flies was assessed in five countries in the African region during 2014 and 2015. Several of these countries were evaluated because of promising results from epidemiological studies in humans. No infective flies were found in two countries. Infective flies were found in the other three, despite the absence of infection in humans (as evaluated by skin-snip microscopy). Ongoing transmission as demonstrated in the black flies could be due to a variety of factors, including lack of treatment of hypo-endemic areas and cross-border issues. Challenges identified during the course of the entomological work suggest that there is a need for improved selection of vector collection sites and vector collection periods in order to improve fly catches. Two important challenges to achieving elimination identified were definition of the hypo-endemic zones and establishing the existence of areas of cross-border transmission occurring between countries.
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Affiliation(s)
- Daniel Boakye
- WHO/AFRO/ESPEN Laboratory, Ouagadougou, Burkina Faso
| | | | - Aime Adjami
- WHO/AFRO/ESPEN Laboratory, Ouagadougou, Burkina Faso
| | | | | | | | | | | | - Laston Sitima
- Onchocerciasis Control Programme, Malawi Ministry of Health, Malawi
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Komlan K, Vossberg PS, Gantin RG, Solim T, Korbmacher F, Banla M, Padjoudoum K, Karabou P, Köhler C, Soboslay PT. Onchocerca volvulus infection and serological prevalence, ocular onchocerciasis and parasite transmission in northern and central Togo after decades of Simulium damnosum s.l. vector control and mass drug administration of ivermectin. PLoS Negl Trop Dis 2018; 12:e0006312. [PMID: 29494606 PMCID: PMC5849363 DOI: 10.1371/journal.pntd.0006312] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 03/13/2018] [Accepted: 02/12/2018] [Indexed: 11/18/2022] Open
Abstract
Background Mass drug administration (MDA) of ivermectin has become the main intervention to control onchocerciasis or “river blindness”. In Togo, after many years of MDA, Onchocerca volvulus infection has declined dramatically, and elimination appears achievable, but in certain river basins the current situation remains unknown. We have conducted parasitological, serological, ophthalmological, and entomological assessments in northern and central Togo within the river basins of Ôti, Kéran and Mô. Methodology/Principal findings Examinations were completed in 1,455 participants from 11 onchocerciasis sentinel villages, and O. volvulus transmission by Simulium damnosum sensu lato (s.l.) was evaluated. In children (aged 1–10 years), the prevalence of microfilariae (Mf) was 2.3% and in adults it ranged from 5.1 to 13.3%. Positive IgG4 responses to O. volvulus adult (crude) worm antigen (OvAg) and the recombinant Ov16 antigen were in all-ages 48.7% and 34.4%, and 29.1% and 14.9% in children, respectively. In the river basin villages of Kéran, Mô and Ôti, the IgG4 seroprevalences to OvAg in children were 51.7%, 23.5% and 12.7%, respectively, and to the Ov16 antigen 33.3% (Kéran) and 5.2% (Ôti). Onchocerciasis ocular lesions (punctate keratitis, evolving iridocyclitis and chorioretinitis) were observed in children and young adults. O. volvulus-specific DNA (Ov150) was detected by poolscreen in vector samples collected from Tchitchira/Kéran(22.8%), Bouzalo/Mô(11.3%), Baghan/Mô(2.9%) and Pancerys/Ôti(4.9%); prevalences of O. volvulus infection in S. damnosum s.l. were, respectively, 1%, 0.5%, 0.1% and 0.2%. Conclusions/Significance In the northern and central river basins in Togo, interruption of O. volvulus transmission has not yet been attained. Patent O. volvulus infections, positive antibody responses, progressive ocular onchocerciasis were diagnosed, and parasite transmission by S. damnosum s.l. occurred close to the survey locations. Future interventions may require approaches selectively targeted to non-complying endemic populations, to the seasonality of parasite transmission and national onchocerciasis control programs should harmonize cross-border MDA as a coordinated intervention. Mass drug administration (MDA) with ivermectin has become the main tool in the efforts to control and eliminate onchocerciasis (“river blindness”). In some areas, and after many years of MDA, levels of Onchocerca volvulus infection (the causative parasite) have declined greatly, and elimination appears achievable. In certain river basins of northern and central Togo, the present epidemiological situation remains unknown. The guidelines of the World Health Organization recommend that before ivermectin MDA can be stopped, interruption of O. volvulus transmission must be demonstrated. To this end, parasitological, serological, ophthalmological, and entomological assessments were conducted in the Ôti, Kéran and Mô river basins. O. volvulus infections and positive antibody responses were found in children aged ≤10 years and adults. Progressive ocular onchocerciasis was diagnosed, and parasite transmission by Simulium damnosum s.l. (the disease vector) occurred close to the survey locations. Thus, O. volvulus transmission continues in northern and central Togo, and future interventions may require approaches selectively adapted to seasonal migration of non-complying endemic populations in and out of the river basins, as well as seasonal transmission by the vectors. National control programmes should harmonize cross-border MDA as a coordinated intervention.
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Affiliation(s)
- Kossi Komlan
- Onchocerciasis Reference Laboratory, National Institute of Hygiene, Sokodé, Togo
| | - Patrick S. Vossberg
- Institute for Tropical Medicine, University of Tübingen, University Clinics, Tübingen, Germany
| | - Richard G. Gantin
- Onchocerciasis Reference Laboratory, National Institute of Hygiene, Sokodé, Togo
- Institute for Tropical Medicine, University of Tübingen, University Clinics, Tübingen, Germany
| | - Tchalim Solim
- Centre Hospitalier Universitaire Campus, Université de Lomé, Lomé, Togo
| | - Francois Korbmacher
- Institute for Tropical Medicine, University of Tübingen, University Clinics, Tübingen, Germany
| | - Méba Banla
- Centre Hospitalier Universitaire Campus, Université de Lomé, Lomé, Togo
| | | | | | - Carsten Köhler
- Institute for Tropical Medicine, University of Tübingen, University Clinics, Tübingen, Germany
| | - Peter T. Soboslay
- Onchocerciasis Reference Laboratory, National Institute of Hygiene, Sokodé, Togo
- Institute for Tropical Medicine, University of Tübingen, University Clinics, Tübingen, Germany
- * E-mail:
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Dissak-Delon FN, Kamga GR, Humblet PC, Robert A, Souopgui J, Kamgno J, Essi MJ, Ghogomu SM, Godin I. Adherence to ivermectin is more associated with perceptions of community directed treatment with ivermectin organization than with onchocerciasis beliefs. PLoS Negl Trop Dis 2017; 11:e0005849. [PMID: 28806785 PMCID: PMC5570488 DOI: 10.1371/journal.pntd.0005849] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 08/24/2017] [Accepted: 08/03/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The fight against onchocerciasis in Africa has boomed thanks to the Community Directed Treatment with Ivermectin (CDTI) program. However, in Cameroon, after more than 15 years of mass treatment, onchocerciasis prevalence is still above the non-transmission threshold. This study aimed to explore a possible association between people's beliefs/perceptions of onchocerciasis and of CDTI program, and their adherence to ivermectin in three regions of Cameroon. METHODOLOGY/PRINCIPAL FINDINGS A cross sectional survey was carried out in three health districts with persistent high onchocerciasis prevalence. Participants were randomly selected in 30 clusters per district. Adherence to ivermectin was comparable between Bafang and Bafia (55.0% and 48.8%, respectively, p>0.05) and lower in Yabassi (40.7%). Among all factors related to program perceptions and disease representations that were studied, perceptions of the program are the ones that were most determinant in adherence to ivermectin. People who had a "not positive" opinion of ivermectin distribution campaigns were less compliant than those who had a positive opinion about the campaigns (40% vs 55% in Bafang, and 48% vs 62% in Bafia, p<0.01), as well as those who had a negative appreciation of community drug distributors' commitment (22% vs 53% in Bafang, 33% vs 59% in Bafia, 27% vs 47% in Yabassi; p<0.01). The most common misconception about onchocerciasis transmission was the lack of hygiene, especially in Bafia and Yabassi. In Bafang, high proportions of people believed that onchocerciasis was due to high consumption of sugar (31% vs less than 5% in Bafia and Yabassi, p<0.001). CONCLUSION/SIGNIFICANCE There are still frequent misconceptions about onchocerciasis transmission in Cameroon. Perceptions of ivermectin distribution campaigns are more strongly associated to adherence. In addition to education/sensitisation on onchocerciasis during the implementation of the CDTI program, local health authorities should strive to better involve communities and more encourage community distributors' work.
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Affiliation(s)
- Fanny Nadia Dissak-Delon
- Ministry of Public Health, Yaoundé, Cameroon
- Université Libre de Bruxelles, Brussels, Belgium
- University of Buea, Buea, Cameroon
| | - Guy-Roger Kamga
- Ministry of Public Health, Yaoundé, Cameroon
- University of Buea, Buea, Cameroon
- Epidemiology and Biostatistics Research Division, Institut de recherche expérimentale et clinique, Université catholique de Louvain, Brussels’ campus, Brussels, Belgium
| | | | - Annie Robert
- Epidemiology and Biostatistics Research Division, Institut de recherche expérimentale et clinique, Université catholique de Louvain, Brussels’ campus, Brussels, Belgium
| | | | - Joseph Kamgno
- Centre for Research on Filariasis and other Tropical Diseases, Yaoundé, Cameroon
- University of Yaoundé I, Yaoundé, Cameroon
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Rodríguez-Pérez MA, Garza-Hernández JA, Salinas-Carmona MC, Fernández-Salas I, Reyes-Villanueva F, Real-Najarro O, Cupp EW, Unnasch TR. The esperanza window trap reduces the human biting rate of Simulium ochraceum s.l. in formerly onchocerciasis endemic foci in Southern Mexico. PLoS Negl Trop Dis 2017; 11:e0005686. [PMID: 28686665 PMCID: PMC5517070 DOI: 10.1371/journal.pntd.0005686] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 07/19/2017] [Accepted: 06/07/2017] [Indexed: 11/18/2022] Open
Abstract
Background The Esperanza Window Trap (EWT) baited with CO2 and human sweat compounds is attractive to Simulium ochraceum s.l., the primary vector of Onchocerca volvulus in the historically largest endemic foci in México and Guatemala. Methodology/Principal findings The ability of the EWT to locally reduce numbers of questing S. ochraceum s.l. was evaluated in two formerly onchocerciasis endemic communities in Southern México. At each community, two EWTs were placed in or near a school or household and flies were collected sequentially for a total of 10 days. Black fly collections were then carried out for an additional 10 days in the absence of the EWTs. Flies were also collected outside the dwellings to control for variations in the local fly populations. When the EWTs were present, there was a significant reduction in the human biting rate at both the household and school locations at collection sites, with a greater effect observed in the schools. Conclusions/Significance These results indicate that the EWTs not only have potential as a black fly monitoring tool but may be used for reducing personal exposure to fly bites in Mesoamerica. The Esperanza window trap (EWT), when used in large numbers (3-4/household and >90% coverage) and baited with human sweat compounds and CO2, can be used to collect epidemiologically significant numbers of Simulium ochraceum s.l., the primary vector of Onchocerca volvulus in the historically largest endemic foci in México and Guatemala. In the present study, we evaluated the ability of the EWT to reduce the personal biting rate by questing S. ochraceum s.l. in two formerly onchocerciasis endemic communities in Southern México. At each community, two EWTs were placed in or near a school or household and flies were collected sequentially for a total of 10 days. Black fly collections were then carried out for an additional 10 days in the absence of the EWTs. When the EWTs were present, there was a significant reduction in the human biting rate at each of the four collection sites, varying from 14% to 51%. This study demonstrates that the EWTs have potential both as a black fly monitoring and personal exposure reduction tool in Mesoamerica.
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Affiliation(s)
- Mario A. Rodríguez-Pérez
- Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa, Tamaulipas, México
- * E-mail: ,
| | - Javier A. Garza-Hernández
- Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa, Tamaulipas, México
- Laboratorio de Biologia Molecular, Universidad Autonoma Agraria Antonio Narro, Unidad Laguna, Torreon, Coahuila. C. P., México
| | | | - Ildefonso Fernández-Salas
- Centro Regional de Investigación en Salud Pública, Instituto Nacional de Salud Pública, Tapachula, Chiapas, México
| | | | - Olga Real-Najarro
- Consejería de Educación, Madrid, España. Calle Maestro 19, Leganés (Madrid) Madrid, España
| | - Eddie W. Cupp
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, United States of America
| | - Thomas R. Unnasch
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida, United States of America
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Poole CB, Li Z, Alhassan A, Guelig D, Diesburg S, Tanner NA, Zhang Y, Evans TC, LaBarre P, Wanji S, Burton RA, Carlow CKS. Colorimetric tests for diagnosis of filarial infection and vector surveillance using non-instrumented nucleic acid loop-mediated isothermal amplification (NINA-LAMP). PLoS One 2017; 12:e0169011. [PMID: 28199317 PMCID: PMC5310896 DOI: 10.1371/journal.pone.0169011] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 11/19/2016] [Indexed: 11/26/2022] Open
Abstract
Accurate detection of filarial parasites in humans is essential for the implementation and evaluation of mass drug administration programs to control onchocerciasis and lymphatic filariasis. Determining the infection levels in vector populations is also important for assessing transmission, deciding when drug treatments may be terminated and for monitoring recrudescence. Immunological methods to detect infection in humans are available, however, cross-reactivity issues have been reported. Nucleic acid-based molecular assays offer high levels of specificity and sensitivity, and can be used to detect infection in both humans and vectors. In this study we developed loop-mediated isothermal amplification (LAMP) tests to detect three different filarial DNAs in human and insect samples using pH sensitive dyes for enhanced visual detection of amplification. Furthermore, reactions were performed in a portable, non-instrumented nucleic acid amplification (NINA) device that provides a stable heat source for LAMP. The efficacy of several strand displacing DNA polymerases were evaluated in combination with neutral red or phenol red dyes. Colorimetric NINA-LAMP assays targeting Brugia Hha I repeat, Onchocerca volvulus GST1a and Wuchereria bancrofti LDR each exhibit species-specificity and are also highly sensitive, detecting DNA equivalent to 1/10-1/5000th of one microfilaria. Reaction times varied depending on whether a single copy gene (70 minutes, O. volvulus) or repetitive DNA (40 min, B. malayi and W. bancrofti) was employed as a biomarker. The NINA heater can be used to detect multiple infections simultaneously. The accuracy, simplicity and versatility of the technology suggests that colorimetric NINA-LAMP assays are ideally suited for monitoring the success of filariasis control programs.
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Affiliation(s)
| | - Zhiru Li
- New England Biolabs, Ipswich, MA United States of America
| | - Andy Alhassan
- New England Biolabs, Ipswich, MA United States of America
| | - Dylan Guelig
- PATH, Seattle, Washington, United States of America
| | | | | | - Yinhua Zhang
- New England Biolabs, Ipswich, MA United States of America
| | | | - Paul LaBarre
- PATH, Seattle, Washington, United States of America
| | - Samuel Wanji
- Research Foundation in Tropical Diseases and Environment, Buea, Cameroon
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Zarroug IMA, Hashim K, ElMubark WA, Shumo ZAI, Salih KAM, ElNojomi NAA, Awad HA, Aziz N, Katabarwa M, Hassan HK, Unnasch TR, Mackenzie CD, Richards F, Higazi TB. The First Confirmed Elimination of an Onchocerciasis Focus in Africa: Abu Hamed, Sudan. Am J Trop Med Hyg 2016; 95:1037-1040. [PMID: 27352878 PMCID: PMC5094213 DOI: 10.4269/ajtmh.16-0274] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 05/16/2016] [Indexed: 11/07/2022] Open
Abstract
Mass treatment with ivermectin for onchocerciasis was stopped in 2012 in Abu Hamed, an isolated focus on the River Nile in northern Sudan. A 3-year posttreatment surveillance (PTS) ensued, at the end of which an evaluation was conducted in 2015 following the current World Health Organization guidelines for verification of onchocerciasis elimination. Vector black flies were collected from sentinel breeding sites and finger-prick bloodspots were collected from children ≤ 10 years of age resident in 35 communities within the focus. Polymerase chain reaction (PCR) screening of 19,191 flies from four sites for the O-150 parasite-specific marker found no flies carrying Onchocerca volvulus larvae (0%, 95% upper confidence limit [UCL] = 0.16), and serological testing of 5,266 children identified only one Ov16 seropositive child (0.019%, 95% UCL = 0.074); whose skin snips were negative when tested by O-150 PCR assay. These results indicate that for the first time in Africa, onchocerciasis elimination has been verified after a successful PTS in Abu Hamed.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Hassan K Hassan
- Global Health Infectious Disease Research Program, College of Public Health, University of South Florida, Tampa, Florida
| | - Thomas R Unnasch
- Global Health Infectious Disease Research Program, College of Public Health, University of South Florida, Tampa, Florida
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Cheke RA, Young S, Garms R. Inverse density dependence of parity rates in the onchocerciasis vector Simulium damnosum s.l. Med Vet Entomol 2016; 30:85-88. [PMID: 26477539 DOI: 10.1111/mve.12145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 05/26/2015] [Accepted: 05/26/2015] [Indexed: 06/05/2023]
Abstract
A correlation between parity rates and an index of adult numbers of Simulium damnosum s.l. (Diptera: Simuliidae) indicates an association, but does not prove causality or show the direction of any causal relationship. The question of whether adult numbers affect parity rates or vice versa is reminiscent of the age-old query of which of the chicken and the egg came first. A method for resolving such issues based on analyses of pairs of time series was proposed by Granger in 1969. When Granger's method was applied to monthly numbers of adult female S. damnosum s.l. caught attempting to bite humans at Asubende, Ghana, and their parity rates, a significant relationship (P = 0.005) emerged, clearly showing that parity rates were dependent on adult numbers. Implications of this inverse density dependence and the results of analyses of other similar time series are presented and discussed.
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Affiliation(s)
- R A Cheke
- Agriculture, Health and Environment Department, Natural Resources Institute, University of Greenwich at Medway, Chatham Maritime, U.K
| | - S Young
- Agriculture, Health and Environment Department, Natural Resources Institute, University of Greenwich at Medway, Chatham Maritime, U.K
| | - R Garms
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
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Eisenbarth A, Achukwi MD, Renz A. Ongoing Transmission of Onchocerca volvulus after 25 Years of Annual Ivermectin Mass Treatments in the Vina du Nord River Valley, in North Cameroon. PLoS Negl Trop Dis 2016; 10:e0004392. [PMID: 26926855 PMCID: PMC4771805 DOI: 10.1371/journal.pntd.0004392] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 12/28/2015] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Recent reports of transmission interruption of Onchocerca volvulus, the causing agent of river blindness, in former endemic foci in the Americas, and more recently in West and East Africa, raise the question whether elimination of this debilitating disease is underway after long-term treatment of the population at risk with ivermectin. The situation in Central Africa has not yet been clearly assessed. METHODS AND FINDINGS Entomologic data from two former endemic river basins in North Cameroon were generated over a period of 43 and 48 months to follow-up transmission levels in areas under prolonged ivermectin control. Moreover, epidemiologic parameters of animal-borne Onchocerca spp. transmitted by the same local black fly vectors of the Simulium damnosum complex were recorded and their impact on O. volvulus transmission success evaluated. With mitochondrial DNA markers we unambiguously confirmed the presence of infective O. volvulus larvae in vectors from the Sudan savannah region (mean Annual Transmission Potential 2009-2012: 98, range 47-221), but not from the Adamawa highland region. Transmission rates of O. ochengi, a parasite of Zebu cattle, were high in both foci. CONCLUSIONS/SIGNIFICANCE The high cattle livestock density in conjunction with the high transmission rates of the bovine filaria O. ochengi prevents the transmission of O. volvulus on the Adamawa plateau, whereas transmission in a former hyperendemic focus was markedly reduced, but not completely interrupted after 25 years of ivermectin control. This study may be helpful to gauge the impact of the presence of animal-filariae for O. volvulus transmission in terms of the growing human and livestock populations in sub-Saharan countries.
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Affiliation(s)
- Albert Eisenbarth
- Institute of Evolution and Ecology, Department of Comparative Zoology, University of Tübingen, Tübingen, Germany
- Programme Onchocercoses field station of the University of Tübingen, Ngaoundéré, Cameroon
| | - Mbunkah Daniel Achukwi
- Veterinary research laboratory, Institute of Agricultural Research for Development, Wakwa Regional Centre, Ngaoundéré, Cameroon
| | - Alfons Renz
- Institute of Evolution and Ecology, Department of Comparative Zoology, University of Tübingen, Tübingen, Germany
- * E-mail:
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Botto C, Basañez MG, Escalona M, Villamizar NJ, Noya-Alarcón O, Cortez J, Vivas-Martínez S, Coronel P, Frontado H, Flores J, Graterol B, Camacho O, Tovar Y, Borges D, Morales AL, Ríos D, Guerra F, Margeli H, Rodriguez MA, Unnasch TR, Grillet ME. Evidence of suppression of onchocerciasis transmission in the Venezuelan Amazonian focus. Parasit Vectors 2016; 9:40. [PMID: 26813296 PMCID: PMC4728794 DOI: 10.1186/s13071-016-1313-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 01/11/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The World Health Organization (WHO) has set goals for onchocerciasis elimination in Latin America by 2015. Most of the six previously endemic countries are attaining this goal by implementing twice a year (and in some foci, quarterly) mass ivermectin (Mectizan®) distribution. Elimination of transmission has been verified in Colombia, Ecuador and Mexico. Challenges remain in the Amazonian focus straddling Venezuela and Brazil, where the disease affects the hard-to-reach Yanomami indigenous population. We provide evidence of suppression of Onchocerca volvulus transmission by Simulium guianense s.l. in 16 previously hyperendemic Yanomami communities in southern Venezuela after 15 years of 6-monthly and 5 years of 3-monthly mass ivermectin treatment. METHODS Baseline and monitoring and evaluation parasitological, ophthalmological, entomological and serological surveys were conducted in selected sentinel and extra-sentinel communities of the focus throughout the implementation of the programme. RESULTS From 2010 to 2012-2015, clinico-parasitological surveys indicate a substantial decrease in skin microfilarial prevalence and intensity of infection; accompanied by no evidence (or very low prevalence and intensity) of ocular microfilariae in the examined population. Of a total of 51,341 S. guianense flies tested by PCR none had L3 infection (heads only). Prevalence of infective flies and seasonal transmission potentials in 2012-2013 were, respectively, under 1% and 20 L3/person/transmission season. Serology in children aged 1-10 years demonstrated that although 26 out of 396 (7%) individuals still had Ov-16 antibodies, only 4/218 (2%) seropositives were aged 1-5 years. CONCLUSIONS We report evidence of recent transmission and morbidity suppression in some communities of the focus representing 75% of the Yanomami population and 70% of all known communities. We conclude that onchocerciasis transmission could be feasibly interrupted in the Venezuelan Amazonian focus.
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Affiliation(s)
- Carlos Botto
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - María-Gloria Basañez
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Faculty of Medicine (St Mary's campus), Imperial College London, London, UK.
| | - Marisela Escalona
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Néstor J Villamizar
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Oscar Noya-Alarcón
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
- Instituto de Medicina Tropical, Facultad de Medicina, Universidad Central de Venezuela, Caracas, Venezuela.
| | - José Cortez
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Sarai Vivas-Martínez
- Cátedra de Salud Pública. Facultad de Medicina (Escuela Luis Razetti), Universidad Central de Venezuela, Caracas, Venezuela.
| | - Pablo Coronel
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Hortencia Frontado
- Instituto de Altos Estudios "Dr. Arnoldo Gabaldón", Ministerio del Poder Popular para la Salud, Maracay, Estado Aragua, Venezuela.
| | - Jorge Flores
- Instituto Geográfico de Venezuela "Simón Bolívar", Caracas, Venezuela.
| | - Beatriz Graterol
- Instituto Nacional de Investigaciones Agrícolas, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Oneida Camacho
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Yseliam Tovar
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Daniel Borges
- Centro Amazónico de Investigación y Control de Enfermedades Tropicales Servicio Autónomo CAICET, Ministerio del Poder Popular para la Salud, Puerto Ayacucho, Estado Amazonas, Venezuela.
| | - Alba Lucia Morales
- Onchocerciasis Elimination Program for the Americas (OEPA), Guatemala City, Guatemala.
| | - Dalila Ríos
- Onchocerciasis Elimination Program for the Americas (OEPA), Guatemala City, Guatemala.
| | - Francisco Guerra
- Instituto Geográfico de Venezuela "Simón Bolívar", Caracas, Venezuela.
| | - Héctor Margeli
- Onchocerciasis Elimination Program for the Americas (OEPA), Guatemala City, Guatemala.
| | | | - Thomas R Unnasch
- Department of Global Health, University of South Florida, Tampa, FL, USA.
| | - María Eugenia Grillet
- Laboratorio de Biología de Vectores y Parásitos, Instituto de Zoología y Ecología Tropical, Facultad de Ciencias, Universidad Central de Venezuela, Apartado Postal 47072, Caracas, 1041-A, Venezuela.
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Hassan HK, Bolcen S, Kubofcik J, Nutman TB, Eberhard ML, Middleton K, Wekesa JW, Ruedas G, Nelson KJ, Dubielzig R, De Lombaert M, Silverman B, Schorling JJ, Adler PH, Unnasch TR, Beeler ES. Isolation of Onchocerca lupi in Dogs and Black Flies, California, USA. Emerg Infect Dis 2016; 21:789-96. [PMID: 25897954 PMCID: PMC4412245 DOI: 10.3201/eid2105.142011] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We implicated the black fly as a vector for this filarial zoonotic parasitic infection. In southern California, ocular infections caused by Onchocerca lupi were diagnosed in 3 dogs (1 in 2006, 2 in 2012). The infectious agent was confirmed through morphologic analysis of fixed parasites in tissues and by PCR and sequencing of amplicons derived from 2 mitochondrially encoded genes and 1 nuclear-encoded gene. A nested PCR based on the sequence of the cytochrome oxidase subunit 1 gene of the parasite was developed and used to screen Simulium black flies collected from southern California for O. lupi DNA. Six (2.8%; 95% CI 0.6%–5.0%) of 213 black flies contained O. lupi DNA. Partial mitochondrial16S rRNA gene sequences from the infected flies matched sequences derived from black fly larvae cytotaxonomically identified as Simulium tribulatum. These data implicate S. tribulatum flies as a putative vector for O. lupi in southern California.
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Richards F, Rizzo N, Diaz Espinoza CE, Monroy ZM, Crovella Valdez CG, de Cabrera RM, de Leon O, Zea-Flores G, Sauerbrey M, Morales AL, Rios D, Unnasch TR, Hassan HK, Klein R, Eberhard M, Cupp E, Domínguez A. One Hundred Years After Its Discovery in Guatemala by Rodolfo Robles, Onchocerca volvulus Transmission Has Been Eliminated from the Central Endemic Zone. Am J Trop Med Hyg 2015; 93:1295-304. [PMID: 26503275 PMCID: PMC4674249 DOI: 10.4269/ajtmh.15-0364] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 07/17/2015] [Indexed: 11/07/2022] Open
Abstract
We report the elimination of Onchocerca volvulus transmission from the Central Endemic Zone (CEZ) of onchocerciasis in Guatemala, the largest focus of this disease in the Americas and the first to be discovered in this hemisphere by Rodolfo Robles Valverde in 1915. Mass drug administration (MDA) with ivermectin was launched in 1988, with semiannual MDA coverage reaching at least 85% of the eligible population in > 95% of treatment rounds during the 12-year period, 2000-2011. Serial parasitological testing to monitor MDA impact in sentinel villages showed a decrease in microfilaria skin prevalence from 70% to 0%, and polymerase chain reaction (PCR)-based entomological assessments of the principal vector Simulium ochraceum s.l. showed transmission interruption by 2007. These assessments, together with a 2010 serological survey in children 9-69 months of age that showed Ov16 IgG4 antibody prevalence to be < 0.1%, meeting World Health Organization (WHO) guidelines for stopping MDA, and treatment was halted after 2011. After 3 years an entomological assessment showed no evidence of vector infection or recrudescence of transmission. In 2015, 100 years after the discovery of its presence, the Ministry of Health of Guatemala declared onchocerciasis transmission as having been eliminated from the CEZ.
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Affiliation(s)
- Frank Richards
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Nidia Rizzo
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Carlos Enrique Diaz Espinoza
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Zoraida Morales Monroy
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Carol Guillermina Crovella Valdez
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Renata Mendizabal de Cabrera
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Oscar de Leon
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Guillermo Zea-Flores
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Mauricio Sauerbrey
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Alba Lucia Morales
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Dalila Rios
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Thomas R Unnasch
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Hassan K Hassan
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Robert Klein
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Mark Eberhard
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Ed Cupp
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
| | - Alfredo Domínguez
- River Blindness Elimination Program, The Carter Center, Atlanta, Georgia; Centro de Estudios en Salud of the Universidad del Valle de Guatemala (UVG), Guatemala City, Guatemala; Ministerio de Salud Pública y Asistencia Social, Guatemala City, Guatemala; Onchocerciasis Elimination Program for the Americas (OEPA), The Carter Center, Guatemala City, Guatemala; Global Health Infectious Disease Program, Department of Global Health, University of South Florida, Tampa, Florida; Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia; Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama
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Rodríguez-Pérez MA, Fernández-Santos NA, Orozco-Algarra ME, Rodríguez-Atanacio JA, Domínguez-Vázquez A, Rodríguez-Morales KB, Real-Najarro O, Prado-Velasco FG, Cupp EW, Richards FO, Hassan HK, González-Roldán JF, Kuri-Morales PA, Unnasch TR. Elimination of Onchocerciasis from Mexico. PLoS Negl Trop Dis 2015; 9:e0003922. [PMID: 26161558 PMCID: PMC4498594 DOI: 10.1371/journal.pntd.0003922] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Accepted: 06/17/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Mexico is one of the six countries formerly endemic for onchocerciasis in Latin America. Transmission has been interrupted in the three endemic foci of that country and mass drug distribution has ceased. Three years after mass drug distribution ended, post-treatment surveillance (PTS) surveys were undertaken which employed entomological indicators to check for transmission recrudescence. METHODOLOGY/PRINCIPAL FINDINGS In-depth entomologic assessments were performed in 18 communities in the three endemic foci of Mexico. None of the 108,212 Simulium ochraceum s.l. collected from the three foci were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in a maximum upper bound of the 95% confidence interval (95%-ULCI) of the infective rate in the vectors of 0.035/2,000 flies examined. This is an order of magnitude below the threshold of a 95%-ULCI of less than one infective fly per 2,000 flies tested, the current entomological criterion for interruption of transmission developed by the international community. The point estimate of seasonal transmission potential (STP) was zero, and the upper bound of the 95% confidence interval for the STP ranged from 1.2 to 1.7 L3/person/season in the different foci. This value is below all previous estimates for the minimum transmission potential required to maintain the parasite population. CONCLUSIONS/SIGNIFICANCE The results from the in-depth entomological post treatment surveillance surveys strongly suggest that transmission has not resumed in the three foci of Mexico during the three years since the last distribution of ivermectin occurred; it was concluded that transmission remains undetectable without intervention, and Onchocerca volvulus has been eliminated from Mexico.
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Affiliation(s)
| | - Nadia A. Fernández-Santos
- Dirección General de Programas Preventivos, Centro Nacional de Programas Preventivos y Control de Enfermedades, Secretaría de Salud, Colonia Escandón, Delegación Miguel Hidalgo, Mexico City, México
| | - María E. Orozco-Algarra
- Dirección General de Programas Preventivos, Centro Nacional de Programas Preventivos y Control de Enfermedades, Secretaría de Salud, Colonia Escandón, Delegación Miguel Hidalgo, Mexico City, México
| | - José A. Rodríguez-Atanacio
- Dirección General de Programas Preventivos, Centro Nacional de Programas Preventivos y Control de Enfermedades, Secretaría de Salud, Colonia Escandón, Delegación Miguel Hidalgo, Mexico City, México
| | | | | | | | - Francisco G. Prado-Velasco
- Programa de Eliminación de la Oncocercosis en Chiapas, Departamento de Prevención y Control de Enfermedades Transmitidas por Vector, Secretaría de Salud Unidad Administrativa, Tuxtla Gutiérrez, Chiapas, México
| | - Eddie W. Cupp
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, United States of America
| | - Frank O. Richards
- River Blindness Program, Carter Center, Atlanta, Georgia, United States of America
| | - Hassan K. Hassan
- Global Health Infectious Disease Research Program, Department of Global Health,University of South Florida, Tampa, Florida, United States of America
| | - Jesús F. González-Roldán
- Dirección General de Programas Preventivos, Centro Nacional de Programas Preventivos y Control de Enfermedades, Secretaría de Salud, Colonia Escandón, Delegación Miguel Hidalgo, Mexico City, México
| | - Pablo A. Kuri-Morales
- Subsecretaría de Prevención y Promoción de la Salud, Secretaría de Salud, Colonia Juárez, Delegación Cuauhtémoc, México, D.F., México
| | - Thomas R. Unnasch
- Global Health Infectious Disease Research Program, Department of Global Health,University of South Florida, Tampa, Florida, United States of America
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Lamberton PHL, Cheke RA, Winskill P, Tirados I, Walker M, Osei-Atweneboana MY, Biritwum NK, Tetteh-Kumah A, Boakye DA, Wilson MD, Post RJ, Basañez MG. Onchocerciasis transmission in Ghana: persistence under different control strategies and the role of the simuliid vectors. PLoS Negl Trop Dis 2015; 9:e0003688. [PMID: 25897492 PMCID: PMC4405193 DOI: 10.1371/journal.pntd.0003688] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 03/09/2015] [Indexed: 11/18/2022] Open
Abstract
Background The World Health Organization (WHO) aims at eliminating onchocerciasis by 2020 in selected African countries. Current control focuses on community-directed treatment with ivermectin (CDTI). In Ghana, persistent transmission has been reported despite long-term control. We present spatial and temporal patterns of onchocerciasis transmission in relation to ivermectin treatment history. Methodology/Principal Findings Host-seeking and ovipositing blackflies were collected from seven villages in four regions of Ghana with 3–24 years of CDTI at the time of sampling. A total of 16,443 flies was analysed for infection; 5,812 (35.3%) were dissected for parity (26.9% parous). Heads and thoraces of 12,196 flies were dissected for Onchocerca spp. and DNA from 11,122 abdomens was amplified using Onchocerca primers. A total of 463 larvae (0.03 larvae/fly) from 97 (0.6%) infected and 62 (0.4%) infective flies was recorded; 258 abdomens (2.3%) were positive for Onchocerca DNA. Infections (all were O. volvulus) were more likely to be detected in ovipositing flies. Transmission occurred, mostly in the wet season, at Gyankobaa and Bosomase, with transmission potentials of, respectively, 86 and 422 L3/person/month after 3 and 6 years of CDTI. The numbers of L3/1,000 parous flies at these villages were over 100 times the WHO threshold of one L3/1,000 for transmission control. Vector species influenced transmission parameters. At Asubende, the number of L3/1,000 ovipositing flies (1.4, 95% CI = 0–4) also just exceeded the threshold despite extensive vector control and 24 years of ivermectin distribution, but there were no infective larvae in host-seeking flies. Conclusions/Significance Despite repeated ivermectin treatment, evidence of O. volvulus transmission was documented in all seven villages and above the WHO threshold in two. Vector species influences transmission through biting and parous rates and vector competence, and should be included in transmission models. Oviposition traps could augment vector collector methods for monitoring and surveillance. The World Health Organization (WHO) aims at eliminating onchocerciasis by 2020 in selected African countries. The success of elimination using ivermectin treatment alone will depend on several interacting factors including baseline endemicity, treatment coverage and vector species mix. In Ghana, transmission persists despite prolonged control. We investigated entomological determinants of this persistence. Blackflies were collected from seven villages with 3–24 years of ivermectin treatment. A total of 12,196 flies was dissected, with 463 larvae (all Onchocerca volvulus) in 97 infected and 62 infective flies. Transmission indices in the wet season, at Gyankobaa and Bosomase, amounted to, respectively, 86 and 422 infective larvae/person/month after 3 and 6 years of ivermectin treatment. Infection levels at these villages were over 100 times the WHO threshold of one L3/1,000 parous flies. At Asubende, an infective fly was caught among ovipositing flies in nearby breeding sites, indicating that infection was just over the WHO threshold despite extensive ivermectin and vector control. Spatial and seasonal vector species composition influences the magnitude of transmission indices through variations in biting and parous rates, and vectorial competence and capacity, and should be reflected in transmission models. Oviposition traps could enhance vector collection for transmission monitoring and surveillance.
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Affiliation(s)
- Poppy H. L. Lamberton
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
- * E-mail:
| | - Robert A. Cheke
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
- Natural Resources Institute, University of Greenwich at Medway, Chatham Maritime, Kent, United Kingdom
| | - Peter Winskill
- MRC Centre for Outbreak Investigation and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Iñaki Tirados
- Natural Resources Institute, University of Greenwich at Medway, Chatham Maritime, Kent, United Kingdom
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Martin Walker
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | | | | | | | - Daniel A. Boakye
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Michael D. Wilson
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Rory J. Post
- School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool, United Kingdom
- Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - María-Gloria Basañez
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
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Svobodová M, Weidinger K, Peške L, Volf P, Votýpka J, Voříšek P. Trypanosomes and haemosporidia in the buzzard (Buteo buteo) and sparrowhawk (Accipiter nisus): factors affecting the prevalence of parasites. Parasitol Res 2014; 114:551-60. [PMID: 25403377 DOI: 10.1007/s00436-014-4217-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 11/05/2014] [Indexed: 11/29/2022]
Abstract
The prevalences of heteroxenous parasites are influenced by the interplay of three main actors: hosts, vectors, and the parasites themselves. We studied blood protists in the nesting populations of raptors in two different areas of the Czech Republic. Altogether, 788 nestlings and 258 adult Eurasian sparrowhawks (Accipiter nisus) and 321 nestlings and 86 adult common buzzards (Buteo buteo) were screened for parasites by the microscopic examination of blood smears and by cultivation. We examined the role of shared vectors and parasite phylogenetic relationships on the occurrence of parasites. In different years and hosts, trypanosome prevalence ranged between 1.9 and 87.2 %, that of Leucocytozoon between 1.9 and 100 %, and Haemoproteus between 0 and 72.7 %. Coinfections with Leucocytozoon and Trypanosoma, phylogenetically distant parasites but both transmitted by blackflies (Simuliidae), were more frequent than coinfections with Leucocytozoon and Haemoproteus, phylogenetically closely related parasites transmitted by different vectors (blackflies and biting midges (Ceratopogonidae), respectively). For example, 16.6 % buzzard nestlings were coinfected with Trypanosoma and Leucocytozoon, while only 4.8 % with Leucocytozoon and Haemoproteus and 0.3 % with Trypanosoma and Haemoproteus. Nestlings in the same nest tended to have the same infection status. Furthermore, prevalence increased with the age of nestlings and with Julian date, while brood size had only a weak negative/positive effect on prevalence at the individual/brood level. Prevalences in a particular avian host species also varied between study sites and years. All these factors should thus be considered while comparing prevalences from different studies, the impact of vectors being the most important. We conclude that phylogenetically unrelated parasites that share the same vectors tend to have similar distributions within the host populations of two different raptor species.
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Affiliation(s)
- Milena Svobodová
- Department of Parasitology, Faculty of Science, Charles University in Prague, Viničná 7, 128 44, Prague 2, Czech Republic,
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Elimination of onchocerciasis in the WHO Region of the Americas: Ecuador’s progress towards verification of elimination. Wkly Epidemiol Rec 2014; 89:401-5. [PMID: 25221799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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Katabarwa M, Lakwo T, Habomugisha P, Agunyo S, Byamukama E, Oguttu D, Ndyomugyenyi R, Tukesiga E, Ochieng GO, Abwaimo F, Onapa A, Lwamafa DWK, Walsh F, Unnasch TR, Richards FO. Transmission of Onchocerca volvulus by Simulium neavei in Mount Elgon focus of Eastern Uganda has been interrupted. Am J Trop Med Hyg 2014; 90:1159-66. [PMID: 24686740 PMCID: PMC4047747 DOI: 10.4269/ajtmh.13-0501] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 02/24/2014] [Indexed: 11/07/2022] Open
Abstract
The study determined that Simulium neavei-transmitted onchocerciasis in Mount Elgon onchocerciasis focus had been interrupted. Annual mass treatment with ivermectin changed to two times per year along with vector elimination in 2007. Then, baseline microfilaria (mf) prevalence data of 1994 in five sentinel communities were compared with follow-up data in 2005 and 2011. Blood spots from 3,051 children obtained in 2009 were analyzed for Onchocerca volvulus immunoglobulin G4 antibodies. Fresh water crab host captures and blackflies collected indicated their infestation with larval stages of S. neavei and presence or absence of the vector, respectively. Mf rates dropped from 62.2% to 0.5%, and 1 (0.03%) of 3,051 children was positive for O. volvulus antibodies. Crab infestation dropped from 41.9% in 2007 to 0%, and S. neavei biting reduced to zero. Both remained zero for the next 3 years, confirming interruption of onchocerciasis transmission, and interventions were halted.
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Affiliation(s)
- Moses Katabarwa
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Tom Lakwo
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Peace Habomugisha
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Stella Agunyo
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Edson Byamukama
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - David Oguttu
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Richard Ndyomugyenyi
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Ephraim Tukesiga
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Galex Orukan Ochieng
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Francis Abwaimo
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Ambrose Onapa
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Dennis W K Lwamafa
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Frank Walsh
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Thomas R Unnasch
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| | - Frank O Richards
- The Carter Center, Atlanta, Georgia; Ministry of Health, Vector Control Division, Kampala, Uganda; The Carter Center Uganda, Kampala, Uganda; Ministry of Health, Kampala, Uganda; Kabarole District Health Services, Kabarole, Uganda; Mbale District Health Services, Mbale, Uganda; Strengthening Decentralization Systems (SDS), Mbale, Uganda; ENVISION/Research Triangle International, Vector Control Division, Ministry of Health, Kampala, Uganda; Lytham St. Anne's, Lancashire, United Kingdom; Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
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Lovato R, Guevara A, Guderian R, Proaño R, Unnasch T, Criollo H, Hassan HK, Mackenzie CD. Interruption of infection transmission in the onchocerciasis focus of Ecuador leading to the cessation of ivermectin distribution. PLoS Negl Trop Dis 2014; 8:e2821. [PMID: 24853587 PMCID: PMC4031166 DOI: 10.1371/journal.pntd.0002821] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 03/11/2014] [Indexed: 11/19/2022] Open
Abstract
Introduction: A clinically significant endemic focus of onchocerciasis existing in Esmeraldas Province, coastal Ecuador has been under an ivermectin mass drug administration program since 1991. The main transmitting vector in this area is the voracious blackfly, Simulium exiguum. This paper describes the assessments made that support the decision to cease mass treatment. Methodology and Principle Findings: Thirty-five rounds of ivermectin treatment occurred between 1991–2009 with 29 of these carrying >85% coverage. Following the guidelines set by WHO for ceasing ivermectin distribution the impact on parasite transmission was measured in the two vector species by an O-150 PCR technique standard for assessing for the presence of Onchocerca volvulus. Up to seven collection sites in three major river systems were tested on four occasions between 1995 and 2008. The infectivity rates of 65.0 (CI 39–101) and 72.7 (CI 42–116) in 1995 dropped to zero at all seven collection sites by 2008. Assessment for the presence of antibodies against O. volvulus was made in 2001, 2006, 2007 and 2008 using standard ELISA assays for detecting anti-Ov16 antibodies. None of total of 1810 children aged 1–15 years (between 82 and 98% of children present in the surveyed villages) tested in the above years were found to be carrying antibodies to this antigen. These findings were the basis for the cessation of mass drug treatment with ivermectin in 2009. Significance: This fulfillment of the criteria for cessation of mass distribution of ivermectin in the only known endemic zone of onchocerciasis in Ecuador moves the country into the surveillance phase of official verification for national elimination of transmission of infection. These findings indicate that ivermectin given twice a year with greater than 85% of the community can move a program to the final stages of verification of transmission interruption. Onchocerciasis has been known to be endemic in the northwestern coastal riverine jungle areas of the country since the early 1980's. A mass drug administration program with ivermectin was implemented in 1991, and in recent years has included consistent twice a year treatment. The impact of this program, and progress towards eliminating the transmission of Onchocerca volvulus from the endemic zone, was assessed by studying entomological parameters at sentinel sites in 1995, 2000, 2004 and 2008 using PCR detection of infective larvae in the vectors (Simulium exiguum and Simulium quadrivittatum); the survey of 2008 showed that all of the collection sites had reached a level consistent with the interruption of transmission. Serological assessment of children and adolescents in 2001–2008 also showed that transmission had been interrupted. These findings support the contention that the Ecuadorian Program has reached the post-treatment surveillance phase of the elimination program; mass drug administration of ivermectin was consequently stopped. The factors contributing to this successful achievement include ivermectin coverage of consistently around 85% or greater since 1998, careful consideration and control of possible expansions of the endemic area through migration, and the maintenance of a strong community health programme.
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Affiliation(s)
- Raquel Lovato
- Ecuadorian Onchocerciasis Program, Ministerio de Salud Pública, Quito, Ecuador
| | - Angel Guevara
- Centro de Biomedicina, Laboratorio de Parasitología Molecular, Escuela de Medicina, Universidad Central del Ecuador, Quito, Ecuador
| | | | - Roberto Proaño
- Ecuadorian Onchocerciasis Program, Ministerio de Salud Pública, Quito, Ecuador
| | - Thomas Unnasch
- GHIDR Program, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Hipatia Criollo
- Centro de Biomedicina, Laboratorio de Parasitología Molecular, Escuela de Medicina, Universidad Central del Ecuador, Quito, Ecuador
| | - Hassan K. Hassan
- GHIDR Program, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Charles D. Mackenzie
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail: ,
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Crainey JL, Mattos-Glória A, Hamada N, Luz SLB. New tools and insights to assist with the molecular identification of Simulium guianense s.l., main Onchocerca volvulus vector within the highland areas of the Amazonia onchocerciasis focus. Acta Trop 2014; 131:47-55. [PMID: 24200838 DOI: 10.1016/j.actatropica.2013.10.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 10/22/2013] [Accepted: 10/25/2013] [Indexed: 11/30/2022]
Abstract
Following the success of the Onchocerciasis Elimination Programme for the Americas (OEPA), there is now just one Latin American onchocerciasis focus where onchocerciasis transmission is described as 'on-going:' the Amazonia Onchocerciasis focus. In the hyperendemic highland areas of the Amazonia focus, Simulium guianense s.l. Wise are the most important vectors of the disease. Populations of S. guianense s.l. are, however, known to vary in their cytogenetics and in a range of behaviours, including in their biting habits. In the hypoendemic lowland areas of the Amazonia focus, for example, S. guianense s.l. are generally regarded as zoophilic and consequently unimportant to disease transmission. Robust tools, to discriminate among various populations of S. guianense s.l. have, however, not yet been developed. In the work reported here, we have assessed the utility of a ribosomal DNA sequence fragment spanning the nuclear ribosomal ITS-1, ITS-2 and 5.8S sequence regions and a ∼850 nucleotide portion of the mitochondrial cytochrome oxidase gene (CO1) for species-level identification and for resolving the within species substructuring. We report here how we have generated 78 CO1 sequences from a rich set of both zoophilic and anthropophilic populations of S. guianense s.l. that were collected from eight sites that are broadly distributed across Brazil. Consistent with previous findings, our analysis supports the genetic isolation of Simulium litobranchium from S. guianense s.l. In contrast with previous findings, however, our results did not provide support for the divergence of the two species prior to the radiation of S. guianense s.l. In our analysis of the S. guianense s.l. ribosomal DNA sequence trace files we generated, we provide clear evidence of multiple within-specimen single nucleotide polymorphisms and indels suggesting that S. guianense s.l. ribosomal DNA is not a good target for conventional DNA barcoding. This is the first report of S. guianense s.l. within individual ribosomal DNA variation and thus the first evidence that the species is not subject to the normal effects of concerted evolution. Collectively, these data illustrate the need for diverse sampling in the development of robust molecular tools for vector identification and suggest that ribosomal DNA might be able to assist with resolving S. guianense s.l. species substructuring that C01 barcoding has hitherto failed to.
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Affiliation(s)
- James L Crainey
- Ecologia de Doenças Transmissíveis na Amazônia, Instituto Leônidas e Maria Deane, Fiocruz Amazônia Rua Terezina, 476. Adrianópolis, CEP: 69057-070 Manaus, AM, Brazil
| | - Aline Mattos-Glória
- Lab de Citotaxonomia e Insetos Aquáticos, Instituto Nacional de Pesquisas da Amazônia-INPA, 69011-970 Manaus, AM, Brazil
| | - Neusa Hamada
- Lab de Citotaxonomia e Insetos Aquáticos, Instituto Nacional de Pesquisas da Amazônia-INPA, 69011-970 Manaus, AM, Brazil
| | - Sérgio L B Luz
- Ecologia de Doenças Transmissíveis na Amazônia, Instituto Leônidas e Maria Deane, Fiocruz Amazônia Rua Terezina, 476. Adrianópolis, CEP: 69057-070 Manaus, AM, Brazil.
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Kaplich VM, Arutiunova KV, Arutiunova MV. [Blackflies (Diptera: Simuliidae) of North of Armenia]. Med Parazitol (Mosk) 2014:37-41. [PMID: 24738226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The fauna of blackflies of North Armenia is represented by 12 species from the genus Simulium. The species composition in the Tavush Region is most diverse (10 species) versus that in the Shirak (n = 5) and Lori (n = 3) Provinces, which is due to a wide variety of Simuliidae breeding sites. Among the bioregulators of blackflies, there are microsporidia of 4 species, cabbageworms (Mermithidae), and caddisflies of the genus Hydropsyche. There is a preponderance of microsporidia among the blackfly bioregulators. The highest percentage (60%) of the larvae infected with microsporidia is noted in the second half of summer, which is related to their environmental conditions.
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Convit J, Schuler H, Borges R, Olivero V, Domínguez-Vázquez A, Frontado H, Grillet ME. Interruption of Onchocerca volvulus transmission in Northern Venezuela. Parasit Vectors 2013; 6:289. [PMID: 24499653 PMCID: PMC3856516 DOI: 10.1186/1756-3305-6-289] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 10/02/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Onchocerciasis is caused by Onchocerca volvulus and transmitted by Simulium species (black flies). In the Americas, the infection has been previously described in 13 discrete regional foci distributed among six countries (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela) where more than 370,000 people are currently considered at risk. Since 2001, disease control in Venezuela has relied on the mass drug administration to the at-risk communities. This report provides empirical evidence of interruption of Onchocerca volvulus transmission by Simulium metallicum in 510 endemic communities from two Northern foci of Venezuela, after 10-12 years of 6-monthly Mectizan (ivermectin) treatment to all the eligible residents. METHODS In-depth entomologic and epidemiologic surveys were serially conducted from 2001-2012 in selected (sentinel and extra-sentinel) communities from the North-central (NC) and North-east (NE) onchocerciasis foci of Venezuela in order to monitor the impact of ivermectin treatment. RESULTS From 2007-2009, entomological indicators in both foci confirmed that 0 out of 112,637 S. metallicum females examined by PCR contained L3 infection in insect heads. The upper bound of the 95% confidence intervals of the infective rate of the vector reached values below 1% by 2009 (NC) and 2012 (NE). Additionally, after 14 (NC) and 22 (NE) rounds of treatment, the seasonal transmission potential (±UL CIs) of S. metallicum was under the critical threshold of 20 L3 per person per season. Serological analysis in school children < 15 years-old demonstrated that 0 out of 6,590 individuals were harboring antibodies to Ov-16. Finally, epidemiological surveys made during 2010 (NC) and 2012 (NE) showed no evidence of microfilariae in the skin and eyes of the population. CONCLUSIONS These results meet the WHO criteria for absence of parasite transmission and disease morbidity in these endemic areas which represent 91% of the population previously at-risk in the country. Consequently, the two Northern foci are currently under post-treatment onchocerciasis surveillance status in Venezuela.
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Affiliation(s)
- Jacinto Convit
- Servicio Autónomo Instituto de Biomedicina & Servicio Regionales de Dermatología Sanitaria, Ministerio del Poder Popular para la Salud, Caracas, Venezuela
| | - Harland Schuler
- Servicio Autónomo Instituto de Biomedicina & Servicio Regionales de Dermatología Sanitaria, Ministerio del Poder Popular para la Salud, Caracas, Venezuela
| | - Rafael Borges
- Servicio Autónomo Instituto de Biomedicina & Servicio Regionales de Dermatología Sanitaria, Ministerio del Poder Popular para la Salud, Caracas, Venezuela
| | - Vimerca Olivero
- Servicio Autónomo Instituto de Biomedicina & Servicio Regionales de Dermatología Sanitaria, Ministerio del Poder Popular para la Salud, Caracas, Venezuela
| | | | - Hortencia Frontado
- Instituto de Altos Estudios “Dr. Arnoldo Gabaldón”, Ministerio del Poder Popular para la Salud, Maracay, Venezuela
| | - María E Grillet
- Laboratorio de Biología de Vectores y Parásitos, Instituto de Zoología y Ecología Tropical, Facultad de Ciencias, Universidad Central de Venezuela, Apartado Postal 47072, Caracas 1041-A, Venezuela
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Rodríguez-Pérez MA, Adeleke MA, Burkett-Cadena ND, Garza-Hernández JA, Reyes-Villanueva F, Cupp EW, Toé L, Salinas-Carmona MC, Rodríguez-Ramírez AD, Katholi CR, Unnasch TR. Development of a novel trap for the collection of black flies of the Simulium ochraceum complex. PLoS One 2013; 8:e76814. [PMID: 24116169 PMCID: PMC3792067 DOI: 10.1371/journal.pone.0076814] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/29/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Human landing collections are currently the standard method for collecting onchocerciasis vectors in Africa and Latin America. As part of the efforts to develop a trap to replace human landing collections for the monitoring and surveillance of onchocerciasis transmission, comprehensive evaluations of several trap types were conducted to assess their ability to collect Simulium ochraceum sensu lato, one of the principal vectors of Onchocerca volvulus in Latin America. METHODOLOGY/PRINCIPAL FINDINGS Diverse trap designs with numerous modifications and bait variations were evaluated for their abilities to collect S. Ochraceum s.l. females. These traps targeted mostly host seeking flies. A novel trap dubbed the "Esperanza window trap" showed particular promise over other designs. When baited with CO2 and BG-lure (a synthetic blend of human odor components) a pair of Esperanza window traps collected numbers of S. Ochraceum s.l. females similar to those collected by a team of vector collectors. CONCLUSIONS/SIGNIFICANCE The Esperanza window trap, when baited with chemical lures and CO2 can be used to collect epidemiologically significant numbers of Simulium ochraceum s.l., potentially serving as a replacement for human landing collections for evaluation of the transmission of O. volvulus.
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Affiliation(s)
- Mario A. Rodríguez-Pérez
- Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa, Tamaulipas, México
- Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México
| | - Monsuru A. Adeleke
- Department of Biological Sciences, Osun State University, Osogbo, Nigeria
| | - Nathan D. Burkett-Cadena
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida, United States of America
| | | | | | - Eddie W. Cupp
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, United States of America
| | - Laurent Toé
- Multidisease Surveillance Centre, World Health Organization, Ouagadougou, Burkina Faso
| | | | - Américo D. Rodríguez-Ramírez
- Centro Regional de Investigación en Salud Pública, Instituto Nacional de Salud Pública, Tapachula, Chiapas, México
| | - Charles R. Katholi
- Department of Biostatistics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Thomas R. Unnasch
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida, United States of America
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Hadis M, Wilson MD, Cobblah M, Boakye DA. Cytotaxonomic description ofSimulium kaffaense, a new member of theS. damnosumcomplex (Diptera: Simuliidae) from south–western Ethiopia. Annals of Tropical Medicine & Parasitology 2013; 99:267-91. [PMID: 15829136 DOI: 10.1179/136485905x24210] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Although Ethiopia is one of the countries worst affected by human onchocerciasis, the exact taxonomic identity of the blackflies acting as the main vectors in the endemic areas has never been determined. A cytotaxonomic analysis of Simulium damnosum s.l. collected from three endemic sites in south-western Ethiopia has now revealed the existence of the 'Kisiwani' form (a non-anthropophilic cytoform that is common in East Africa) and a newly recognized species, Simulium kaffaense. Simulium kaffaense sp. nov. is differentiated from other members of the S. damnosum complex by six fixed inversions and dozens of 'new' floating inversions. The rearing of egg batches from some of the biting adult females, to larvae or adults, indicated that the human-biting blackflies were all S. kaffaense. As S. kaffaense is not only highly anthropophilic but also, apparently, the only anthropophilic member of the S. damnosum complex present, it is likely to be the main (if not the only) vector of Onchocerca volvulus in the study area. The presence of inversion 1S-1 and a complex inversion possibly involving 1L-3 indicates that S. kaffaense either belongs or is close to the 'Nile' phylogenetic group of S. damnosum s. l. The karyotype frequencies of the inversions in the collections from the three study sites indicate that at least two forms of S. kaffaense, here designated 'Bebeka' and 'Jimma', were caught. The taxonomy and medical importance of S. kaffaense are discussed.
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Affiliation(s)
- M Hadis
- Noguchi Memorial Institute for Medical Research, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana
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Mustapha M, Krüger A, Tambala PAJ, Post RJ. Incrimination ofSimulium thyolense(Diptera: Simuliidae) as the anthropophilic blackfly in the Thyolo focus of human onchocerciasis in Malawi. Annals of Tropical Medicine & Parasitology 2013; 99:181-92. [PMID: 15814037 DOI: 10.1179/136485905x24238] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The sibling species of the Simulium damnosum complex that are potential vectors in the foci of human onchocerciasis found in southern Malawi (the southern-most foci in Africa) were identified, using a combination of cytotaxonomic and molecular techniques. Simulium thyolense was found to be the most abundant species within the foci (representing 91% of the larvae collected), whilst S. kilibanum and cytoforms of the 'Ketaketa' subcomplex were the dominant members of the complex found outside of the foci. As all 188 biting female flies collected from the Thyolo, Mwanza and Mulanje foci were identified as S. thyolense, this species is probably the only significant vector of Onchocerca volvulus in the area, and the other Simulium species collected are assumed to be zoophilic. The results confirm the diagnostic value of the size of the amplicon(s) produced in PCR based on the sequences coding for the internal-transcribed-spacer region of the nuclear ribosomal DNA (ITS-1 rDNA), with a characteristic 340bp amplicon for S. thyolense. Chromosomal polymorphisms within S. thyolense indicate some degree of geographical isolation of the 'Thyolo-Mulanje' focus from the Mwanza focus.
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Affiliation(s)
- M Mustapha
- Department of Entomology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Higazi TB, Zarroug IMA, Mohamed HA, Elmubark WA, Deran TCM, Aziz N, Katabarwa M, Hassan HK, Unnasch TR, Mackenzie CD, Richards F, Hashim K. Interruption of Onchocerca volvulus transmission in the Abu Hamed focus, Sudan. Am J Trop Med Hyg 2013; 89:51-7. [PMID: 23690554 PMCID: PMC3748488 DOI: 10.4269/ajtmh.13-0112] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 04/09/2013] [Indexed: 11/07/2022] Open
Abstract
Abu Hamed, Sudan, the northernmost location of onchocerciasis in the world, began community-directed treatment with ivermectin (CDTI) in 1998, with annual treatments enhanced to semiannual in 2007. We assessed the status of the parasite transmission in 2011 entomologically, parasitologically, and serologically. O-150 pool screening showed no parasite DNA in 17,537 black flies collected in 2011 (95% confidence interval upper limit [95% CI UL] = 0.023). Skin microfilariae, nodules, and signs of skin disease were absent in 536 individuals in seven local communities. Similarly, no evidence of Onchocerca volvulus Ov16 antibodies was found in 6,756 school children ≤ 10 years (95% CI UL = 0.03%). Because this assessment of the focus meets the 2001 World Health Organization (WHO) criteria for interrupted transmission, treatment was halted in 2012, and a post-treatment surveillance period was initiated in anticipation of declaration of disease elimination in this area. We provide the first evidence in East Africa that long-term CDTI alone can interrupt transmission of onchocerciasis.
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Affiliation(s)
- Tarig B Higazi
- Department of Biological Sciences, Ohio University, Zanesville, OH, USA.
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