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Mushi VP, Bhwana D, Massawe IS, Makunde W, Sebukoto H, Ngasa W, Sengerema J, Mhina A, Hayuma PM, Kimambo H, Kidima W, Matuja W, Sander JW, Cross H, Sen A, Colebunders R, Newton CR, Mmbando BP. Prevalence of onchocerciasis and epilepsy in a Tanzanian region after a prolonged community-directed treatment with ivermectin. PLoS Negl Trop Dis 2024; 18:e0012470. [PMID: 39241094 PMCID: PMC11410205 DOI: 10.1371/journal.pntd.0012470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 09/18/2024] [Accepted: 08/18/2024] [Indexed: 09/08/2024] Open
Abstract
INTRODUCTION Epidemiological evidence suggests that Onchocerca volvulus is associated with epilepsy, although the exact pathophysiological mechanism is unknown. Mahenge is an endemic focus of onchocerciasis, with the longest-running ivermectin treatment intervention in Tanzania. We assessed the prevalence of onchocerciasis and epilepsy after 25 years of control using ivermectin. METHODS This was a population-based cross-sectional study in 34 villages in Mahenge in 2021. Community health workers conducted door-to-door household surveys to enumerate the population and screen for individuals suspected of epilepsy using a standardised questionnaire. Trained physicians confirmed epilepsy. Children aged 6-11 years were screened for onchocerciasis antibodies using the Ov16 rapid test. Villages were stratified into three altitude levels (low [<400], medium [400-950], and high [>950 meters above sea level]) as a proxy for rapids, which black flies favour for breeding sites. Incidence of epilepsy was estimated as a ratio of new cases in the year preceding the survey per 100,000 population. RESULTS 56,604 individuals (median age 20.2 years, 51.1% females) were surveyed. Onchocerciasis prevalence in children was 11.8% and was highest in villages at medium (21.7%) and lowest in low altitudes (3.2%), p<0.001. Self-reported use of ivermectin was 88.4%. Epilepsy prevalence was 21.1 (95%CI: 19.9-22.3) cases per 1000 persons and was highest in medium (29.5%) and lowest in the lowlands (12.7%). The odds ratio (OR) of having epilepsy was significantly higher in females (OR = 1.22, 95%CI: 1.08-1.38), middle altitudes (OR = 2.34 [95%CI: 2.04-2.68]), and in individuals positive for OV16 (OR = 1.98 [95%CI:1.57-2.50]). The incidence of epilepsy a year before the survey was 117 (95%CI: 99.7-160.4) cases per 100,000 person-years. CONCLUSION Despite ivermectin use for 25 years, the prevalence of onchocerciasis and epilepsy remains high. It is crucial to strengthen bi-annual ivermectin treatment and initiate interventions targeting vectors to control onchocerciasis and epilepsy in the area.
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Affiliation(s)
- Vivian P Mushi
- Department of Parasitology and Medical Entomology, School of Public Health and Social Sciences, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
- Department of Zoology and Wildlife Conservation, College of Natural and Applied Sciences, University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Dan Bhwana
- Tanga Research Centre, National Institute for Medical Research, Tanga, Tanzania
| | - Isolide S Massawe
- Tanga Research Centre, National Institute for Medical Research, Tanga, Tanzania
| | - Williams Makunde
- Tanga Research Centre, National Institute for Medical Research, Tanga, Tanzania
| | - Hillary Sebukoto
- Tanga Research Centre, National Institute for Medical Research, Tanga, Tanzania
| | | | | | - Athanas Mhina
- Tanga Research Centre, National Institute for Medical Research, Tanga, Tanzania
| | - Paul M Hayuma
- Tanga Research Centre, National Institute for Medical Research, Tanga, Tanzania
| | - Henrika Kimambo
- Department of Internal Medicine, Muhimbili National Hospital, Dar es Salaam, Tanzania
| | - Winifrida Kidima
- Department of Zoology and Wildlife Conservation, College of Natural and Applied Sciences, University of Dar es Salaam, Dar es Salaam, Tanzania
| | - William Matuja
- Department of Neurology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Josemir W Sander
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG & Chalfont Centre for Epilepsy, London, United Kingdom
- Neurology Department, West China Hospital, Sichuan University, Chengdu, China
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands
| | - Helen Cross
- Developmental Neurosciences Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Arjune Sen
- Oxford Epilepsy Research Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | | | - Charles R Newton
- Oxford Epilepsy Research Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neuroscience Unit, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom
| | - Bruno P Mmbando
- Tanga Research Centre, National Institute for Medical Research, Tanga, Tanzania
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Khainza AT, Soita D, Okia D, Okello F, Matovu JKB, Lubaale Y, Byamukama E, Okibure A, Alunyo JP, Nantale R, Wanume B, Ogutu D, Mukunya D, Olupot-Olupot P. Community Involvement in Onchocerciasis Post-elimination Surveillance in Bududa District, Eastern Uganda: A cross-sectional study. PLoS Negl Trop Dis 2024; 18:e0012270. [PMID: 39012847 PMCID: PMC11251607 DOI: 10.1371/journal.pntd.0012270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 06/04/2024] [Indexed: 07/18/2024] Open
Abstract
BACKGROUND Globally, there are an estimated 20.9 million cases of onchocerciasis, with Africa bearing the greatest burden. The World Health Organization (WHO) has targeted the disease for elimination by 2030. As of August 2023, there were 15 foci in 37/48 (76%) districts and one city in Uganda that had reached the elimination phase. However, there is a paucity of data on community involvement in post-elimination surveillance (PES) activities. The communities in the post-elimination phase are expected to maintain surveillance, provide health education, refer cases for treatment, and participate in surveillance. However, it is not clear whether this is being done. In this study, we assessed the feasibility of community involvement in post-elimination surveillance activities in Bududa District, Eastern Uganda, to draw key generalisable lessons for similar settings. METHODS This was a cross-sectional study employing rigorous mixed methods of data collection. We used a semi-structured questionnaire to collect quantitative data on randomly sampled study participants in two sub-countries in the district. Community involvement in post-elimination surveillance (PES) was our dependent variable, measured using Yes or No questions, and our independent variables were measured on different scales. Computations of proportions and associations were done using Stata 15 software. Conversely, qualitative data were collected via focus group discussions (FGDs) for community participants and key informant interviews (KIIs) for local leaders. For the qualitative component, we had 2 FGDs, each consisting of 8 gender-balanced participants per group and 8 KIIs. Qualitative data analyses were done using a robust thematic framework approach, ensuring the reliability and validity of our findings. RESULTS A total of 422 participants with a mean age of 51.4 years (SD = 15.8) participated in the study. Community involvement in post-elimination surveillance was low (14%). Factors associated with involvements were district support [Adjusted odd ratio AOR 14, 95 CI = (2.5, 81.7)], seeing black flies in the environment in a week preceding the survey [AOR 8, 95% CI = (1.5, 42.5)], in one month [AOR 3.8, 95% CI = (1.1, 13.2)], and being a community volunteer in the Ivermectin treatment program [AOR 4.3, 95% CI = (1.03, 17.9)]. Lack of funding, poor motivation, poor program sustainability planning, and a lack of drugs at health facilities were key challenges affecting community involvement in post-elimination surveillance. CONCLUSION Community involvement in onchocerciasis post-elimination surveillance activities in Bududa District in Eastern Uganda was low but could be improved by increased district support, funding, community motivation and sensitisation.
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Affiliation(s)
- Annet Tabitha Khainza
- Department of Community and Public Health, Busitema University, Mbale, Uganda
- The Carter Center, Kampala, Uganda
| | - David Soita
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | - David Okia
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | - Francis Okello
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | - Joseph KB Matovu
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | - Yovani Lubaale
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | | | - Ambrose Okibure
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | | | - Ritah Nantale
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | - Benon Wanume
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | | | - David Mukunya
- Department of Community and Public Health, Busitema University, Mbale, Uganda
| | - Peter Olupot-Olupot
- Department of Community and Public Health, Busitema University, Mbale, Uganda
- Department of Research, Mbale Clinical Research Institute, Mbale, Uganda
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Mutono N, Basáñez MG, James A, Stolk WA, Makori A, Kimani TN, Hollingsworth TD, Vasconcelos A, Dixon MA, de Vlas SJ, Thumbi SM. Elimination of transmission of onchocerciasis (river blindness) with long-term ivermectin mass drug administration with or without vector control in sub-Saharan Africa: a systematic review and meta-analysis. Lancet Glob Health 2024; 12:e771-e782. [PMID: 38484745 PMCID: PMC11009120 DOI: 10.1016/s2214-109x(24)00043-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 01/11/2024] [Accepted: 01/19/2024] [Indexed: 04/15/2024]
Abstract
BACKGROUND WHO has proposed elimination of transmission of onchocerciasis (river blindness) by 2030. More than 99% of cases of onchocerciasis are in sub-Saharan Africa. Vector control and mass drug administration of ivermectin have been the main interventions for many years, with varying success. We aimed to identify factors associated with elimination of onchocerciasis transmission in sub-Saharan Africa. METHODS For this systematic review and meta-analysis we searched for published articles reporting epidemiological or entomological assessments of onchocerciasis transmission status in sub-Saharan Africa, with or without vector control. We searched MEDLINE, PubMed, Web of Science, Embase, Cochrane Central Register of Controlled Trials, African Index Medicus, and Google Scholar databases for all articles published from database inception to Aug 19, 2023, without language restrictions. The search terms used were "onchocerciasis" AND "ivermectin" AND "mass drug administration". The three inclusion criteria were (1) focus or foci located in Africa, (2) reporting of elimination of transmission or at least 10 years of ivermectin mass drug administration in the focus or foci, and (3) inclusion of at least one of the following assessments: microfilarial prevalence, nodule prevalence, Ov16 antibody seroprevalence, and blackfly infectivity prevalence. Epidemiological modelling studies and reviews were excluded. Four reviewers (NM, AJ, AM, and TNK) extracted data in duplicate from the full-text articles using a data extraction tool developed in Excel with columns recording the data of interest to be extracted, and a column where important comments for each study could be highlighted. We did not request any individual-level data from authors. Foci were classified as achieving elimination of transmission, being close to elimination of transmission, or with ongoing transmission. We used mixed-effects meta-regression models to identify factors associated with transmission status. This study is registered in PROSPERO, CRD42022338986. FINDINGS Of 1525 articles screened after the removal of duplicates, 75 provided 282 records from 238 distinct foci in 19 (70%) of the 27 onchocerciasis-endemic countries in sub-Saharan Africa. Elimination of transmission was reported in 24 (9%) records, being close to elimination of transmission in 86 (30%) records, and ongoing transmission in 172 (61%) records. I2 was 83·3% (95% CI 79·7 to 86·3). Records reporting 10 or more years of continuous mass drug administration with 80% or more therapeutic coverage of the eligible population yielded significantly higher odds of achieving elimination of transmission (log-odds 8·5 [95% CI 3·5 to 13·5]) or elimination and being close to elimination of transmission (42·4 [18·7 to 66·1]) than those with no years achieving 80% coverage or more. Reporting 15-19 years of ivermectin mass drug administration (22·7 [17·2 to 28·2]) and biannual treatment (43·3 [27·2 to 59·3]) were positively associated with elimination and being close to elimination of transmission compared with less than 15 years and no biannual mass drug administration, respectively. Having had vector control without vector elimination (-42·8 [-59·1 to -26·5]) and baseline holoendemicity (-41·97 [-60·6 to -23·2]) were associated with increased risk of ongoing transmission compared with no vector control and hypoendemicity, respectively. Blackfly disappearance due to vector control or environmental change contributed to elimination of transmission. INTERPRETATION Mass drug administration duration, frequency, and coverage; baseline endemicity; and vector elimination or disappearance are important determinants of elimination of onchocerciasis transmission in sub-Saharan Africa. Our findings underscore the importance of improving and sustaining high therapeutic coverage and increasing treatment frequency if countries are to achieve elimination of onchocerciasis transmission. FUNDING The Bill & Melinda Gates Foundation and Neglected Tropical Diseases Modelling Consortium, UK Medical Research Council, and Global Health EDCTP3 Joint Undertaking. TRANSLATIONS For the Swahili, French, Spanish and Portuguese translations of the abstract see Supplementary Materials section.
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Affiliation(s)
- Nyamai Mutono
- Centre for Epidemiological Modelling and Analysis, University of Nairobi, Nairobi, Kenya; Paul G Allen School for Global Health, Washington State University, Pullman, WA, USA.
| | - Maria-Gloria Basáñez
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK; London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
| | - Ananthu James
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Anita Makori
- Centre for Epidemiological Modelling and Analysis, University of Nairobi, Nairobi, Kenya; Paul G Allen School for Global Health, Washington State University, Pullman, WA, USA
| | - Teresia Njoki Kimani
- Centre for Epidemiological Modelling and Analysis, University of Nairobi, Nairobi, Kenya; Paul G Allen School for Global Health, Washington State University, Pullman, WA, USA; Ministry of Health Kenya, Kiambu Town, Kenya
| | | | | | - Matthew A Dixon
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK; London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - S M Thumbi
- Centre for Epidemiological Modelling and Analysis, University of Nairobi, Nairobi, Kenya; Paul G Allen School for Global Health, Washington State University, Pullman, WA, USA; Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, UK
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Capture of high numbers of Simulium vectors can be achieved with Host Decoy Traps to support data acquisition in the onchocerciasis elimination endgame. Acta Trop 2021; 221:106020. [PMID: 34157291 PMCID: PMC8326245 DOI: 10.1016/j.actatropica.2021.106020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 05/25/2021] [Accepted: 06/12/2021] [Indexed: 11/24/2022]
Abstract
Onchocerciasis elimination is within reach in many countries but requires enhanced surveillance of the Simulium vectors of Onchocerca volvulus. Collection of sufficient numbers of adult Simulium to detect infective O. volvulus larvae is hindered by limited sampling tools for these flies. Here, we tested for the first time the Host Decoy Trap (HDT), an exposure free method previously developed for Anopheles vectors of malaria parasites, as a potential sampling tool for adult Simulium. In three replicates of a randomized Latin square experimental design, the HDT was compared to Human Landing Catches (HLC) and the Esperanza Window Trap (EWT). A total of 8,531 adult S. damnosum sensu lato blackflies (S. squamosum group) were found in catches from the three different trapping methods. The HDT (mean catch 533 ± 111) caught significantly more S. squamosum than the EWT (mean catch 9.1 ± 2.2), a nearly 60-fold difference. There was no significant difference between the HLC (mean catch 385.6 ± 80.9) and the HDT. Larvae indistinguishable from those of O. volvulus were dissected from 2.86% of HDT samples (n = 70) and 0.35% of HLC samples (n = 285); a single infective third-stage larvae (L3) was found during dissection of a sample from the HDT. Owing to its very high capture rate, which was comparable to the HLC and significantly greater than EWT, alongside the presence of infected flies in its catch, the HDT represents a potentially valuable new tool for blackfly collection in elimination settings, where thousands of flies are needed for parasite screening.
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Forrer A, Wanji S, Obie ED, Nji TM, Hamill L, Ozano K, Piotrowski H, Dean L, Njouendou AJ, Ekanya R, Ndongmo WPC, Fung EG, Nnamdi DB, Abong RA, Beng AA, Eyong ME, Ndzeshang BL, Nkimbeng DA, Teghen S, Suireng A, Ashu EE, Kah E, Murdoch MM, Thomson R, Theobald S, Enyong P, Turner JD, Taylor MJ. Why onchocerciasis transmission persists after 15 annual ivermectin mass drug administrations in South-West Cameroon. BMJ Glob Health 2021; 6:bmjgh-2020-003248. [PMID: 33431378 PMCID: PMC7802695 DOI: 10.1136/bmjgh-2020-003248] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 11/11/2020] [Accepted: 11/27/2020] [Indexed: 12/11/2022] Open
Abstract
Introduction Onchocerciasis is targeted for elimination mainly with annual community-directed treatment with ivermectin (CDTI). High infection levels have been reported in South-West Cameroon, despite ≥15 years of CDTI. The aim of this study was to assess factors associated with continued onchocerciasis transmission and skin disease. Methods A large-scale cross-sectional study was conducted in 2017 in 20 communities in a loiasis-risk area in South-West Cameroon. A mixed-methods approach was used. Associations between infection levels, skin disease and adherence to CDTI were assessed using mixed regression modelling. Different community members’ perception and acceptability of the CDTI strategy was explored using semi-structured interviews. Results Onchocerciasis prevalence was 44.4% among 9456 participants. 17.5% of adults were systematic non-adherers and 5.9% participated in ≥75% of CDTI rounds. Skin disease affected 1/10 participants, including children. Increasing self-reported adherence to CDTI was associated with lower infection levels in participants aged ≥15 years but not in children. Adherence to CDTI was positively influenced by perceived health benefits, and negatively influenced by fear of adverse events linked with economic loss. Concern of lethal adverse events was a common reason for systematic non-adherence. Conclusion CDTI alone is unlikely to achieve elimination in those high transmission areas where low participation is commonly associated with the fear of adverse events, despite the current quasi absence of high-risk levels of loiasis. Such persisting historical memories and fear of ivermectin might impact adherence to CDTI also in areas with historical presence but current absence of loiasis. Because such issues are unlikely to be tackled by CDTI adaptive measures, alternative strategies are needed for onchocerciasis elimination where negative perception of ivermectin is an entrenched barrier to community participation in programmes.
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Affiliation(s)
- Armelle Forrer
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, UK
| | - Samuel Wanji
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Elisabeth Dibando Obie
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Theobald Mue Nji
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Department of Sociology and Anthropology, University of Buea, Buea, Cameroon
| | - Louise Hamill
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, UK
| | - Kim Ozano
- Department of International Public Health, Liverpool School of Tropical Medicine, Liverpool, Liverpool, UK
| | - Helen Piotrowski
- Department of International Public Health, Liverpool School of Tropical Medicine, Liverpool, Liverpool, UK
| | - Laura Dean
- Department of International Public Health, Liverpool School of Tropical Medicine, Liverpool, Liverpool, UK
| | - Abdel J Njouendou
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Relindis Ekanya
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Winston Patrick Chounna Ndongmo
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Ebua Gallus Fung
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Department of Sociology and Anthropology, University of Buea, Buea, Cameroon
| | - Dum-Buo Nnamdi
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Department of Sociology and Anthropology, University of Buea, Buea, Cameroon
| | - Raphael A Abong
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Amuam Andrew Beng
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Mathias Esum Eyong
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Bertrand L Ndzeshang
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Desmond Akumtoh Nkimbeng
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Samuel Teghen
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Anicetus Suireng
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Ernerstine Ebot Ashu
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Emmanuel Kah
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Michele M Murdoch
- Watford General Hospital, West Herts Hospitals NHS Trust, Watford, UK
| | - Rachael Thomson
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, UK
| | - Sally Theobald
- Department of International Public Health, Liverpool School of Tropical Medicine, Liverpool, Liverpool, UK
| | - Peter Enyong
- Department of Disease Control, Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Joseph D Turner
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, UK
| | - Mark J Taylor
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, Merseyside, UK
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Jacob B, Loum D, Munu D, Lakwo T, Byamukama E, Habomugisha P, Cupp EW, Unnasch TR. Optimization of Slash and Clear Community-Directed Control of Simulium damnosum Sensu Stricto in Northern Uganda. Am J Trop Med Hyg 2021; 104:1394-1403. [PMID: 33432900 DOI: 10.4269/ajtmh.20-1104] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 11/10/2020] [Indexed: 11/07/2022] Open
Abstract
Onchocerciasis, caused by infection with Onchocerca volvulus, has been targeted for elimination by 2030. Currently, onchocerciasis elimination programs rely primarily on mass distribution of ivermectin. However, ivermectin alone may not be sufficient to achieve elimination in some circumstances, and additional tools may be needed. Vector control has been used as a tool to control onchocerciasis, but vector control using insecticides is expensive and ecologically detrimental. Community-directed removal of the trailing vegetation blackfly larval attachment sites (slash and clear) has been shown to dramatically reduce vector biting densities. Here, we report studies to optimize the slash and clear process. Conducting slash and clear interventions at Simulium damnosum sensu stricto breeding sites located within 2 km of afflicted communities resulted in a 95% reduction in vector biting. Extending slash and clear further than 2 km resulted in no further decrease. A single intervention conducted at the first half of the rainy season resulted in a 97% reduction in biting rate, whereas an intervention conducted at the end of the rainy season resulted in a 94% reduction. Vector numbers in any of the intervention villages did not fully recover by the start of the following rainy season. These results suggest that slash and clear may offer an inexpensive and effective way to augment ivermectin distribution in the effort to eliminate onchocerciasis in Africa.
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Affiliation(s)
- Benjamin Jacob
- College of Public Health, University of South Florida, Tampa, Florida
| | - Denis Loum
- Nwoya District Local Government, Nwoya, Uganda
| | - Denis Munu
- The Carter Center, Uganda Office, Kampala, Uganda
| | - Thomson Lakwo
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | | | - Eddie W Cupp
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida
| | - Thomas R Unnasch
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida
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7
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Lakwo T, Oguttu D, Ukety T, Post R, Bakajika D. Onchocerciasis Elimination: Progress and Challenges. Res Rep Trop Med 2020; 11:81-95. [PMID: 33117052 PMCID: PMC7548320 DOI: 10.2147/rrtm.s224364] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 08/16/2020] [Indexed: 01/08/2023] Open
Abstract
Onchocerciasis is a parasitic infection caused by the filarial nematode Onchocerca volvulus and transmitted through the bites of black flies of the genus Similium that breed in rivers and streams. The impact of mass treatment with ivermectin and supplemented by vector control in some countries has changed the global scene of onchocerciasis. There has been reported progress made in elimination of onchocerciasis in central and southern American countries and in some localities in Africa. The target for elimination in the Americas has been set at 2022 while for 12 countries in Africa this is expected in 2030. This review was conducted to examine the current status of onchocerciasis elimination at the global level and report on progress made. Literature searches were made through PubMed, articles in English or English abstracts, reports and any other relevant articles related to the subject. The global burden of onchocerciasis is progressively reducing and is no longer a public health problem in some regions. However, programs are challenged with a range of issues: cross-border transmission, diagnostic tools, Loa loa co-endemicity, limited workforce in entomology and maintaining enthusiasm among community drug distributors. More concerted effort using appropriate tools is required to overcome the challenges.
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Affiliation(s)
- Thomson Lakwo
- Neglected Tropical Disease Control Program, Vector Control Division, Ministry of Health, Kampala, Uganda
| | - David Oguttu
- Neglected Tropical Disease Control Program, Vector Control Division, Ministry of Health, Kampala, Uganda
| | - Tony Ukety
- Centre de Recherche pour les Maladies Tropicales, Rethy, Ituri Province, The Democratic Republic of the Congo
| | - Rory Post
- Disease Control Department, London School of Hygiene & Tropical Medicine, London, UK.,School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
| | - Didier Bakajika
- Expanded Special Project for Elimination of Neglected Tropical Diseases, WHO Regional Office for Africa, Brazzaville, Congo
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8
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Differential susceptibility of Onchocerca volvulus microfilaria to ivermectin in two areas of contrasting history of mass drug administration in Cameroon: relevance of microscopy and molecular techniques for the monitoring of skin microfilarial repopulation within six months of direct observed treatment. BMC Infect Dis 2020; 20:726. [PMID: 33008333 PMCID: PMC7530974 DOI: 10.1186/s12879-020-05444-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 09/23/2020] [Indexed: 11/24/2022] Open
Abstract
Background Ivermectin is an excellent microfilaricide against Onchocerca volvulus. However, in some regions, long term use of ivermectin has resulted in sub-optimal responses to the treatment. More data to properly document the phenomenon in various contexts of ivermectin mass drug administration (IVM-MDA) is needed. Also, there is a need to accurately monitor a possible repopulation of skin by microfilariae following treatment. Skin snip microscopy is known to have a low sensitivity in individuals with light infections, which can be the case following treatment. This study was designed with two complementary objectives: (i) to assess the susceptibility of O. volvulus microfilariae to ivermectin in two areas undergoing IVM-MDA for different lengths of time, and (ii) to document the repopulation of skin by the O. volvulus microfilariae following treatment, using 3 independent diagnostic techniques. Method Identified microfilaridermic individuals were treated with ivermectin and re-examined after 1, 3, and 6 months using microscopy, actin real-time PCR (actin-qPCR) and O-150 LAMP assays. Susceptibility to ivermectin and trends in detecting reappearance of skin microfilariae were determined using three techniques. Microscopy was used as an imperfect gold standard to determine the performance of actin-qPCR and LAMP. Results In Bafia with over 20 years of IVM-MDA, 11/51 (21.6%) direct observe treated microfilaridemic participants were still positive for skin microfilariae after 1 month. In Melong, with 10 years of IVM-MDA, 2/29 (6.9%) treated participants were still positive. The microfilarial density reduction per skin biopsy within one month following treatment was significantly lower in participants from Bafia. In both study sites, the molecular techniques detected higher proportions of infected individuals than microscopy at all monitoring time points. LAMP demonstrated the highest levels of sensitivity and real-time PCR was found to have the highest specificity. Conclusion Patterns in skin mirofilariae clearance and repopulation were established. O. volvulus worms from Bafia with higher number of annual MDA displayed a lower clearance and higher repopulation rate after treatment with ivermectin. Molecular assays displayed higher sensitivity in monitoring O. volvulus microfilaridemia within six months following treatment.
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9
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Johnson TP, Sejvar J, Nutman TB, Nath A. The Pathogenesis of Nodding Syndrome. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2020; 15:395-417. [PMID: 31977293 DOI: 10.1146/annurev-pathmechdis-012419-032748] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Nodding syndrome is a rare, enigmatic form of pediatric epilepsy that has occurred in an epidemic fashion beginning in the early 2000s in geographically distinct regions of Africa. Despite extensive investigation, the etiology of nodding syndrome remains unclear, although much progress has been made in understanding the pathogenesis of the disease, as well as in treatment and prevention. Nodding syndrome is recognized as a defined disease entity, but it is likely one manifestation along a continuum of Onchocerca volvulus-associated neurological complications. This review examines the epidemiology of nodding syndrome and its association with environmental factors. It provides a critical analysis of the data that support or contradict the leading hypotheses of the etiologies underlying the pathogenesis of the syndrome. It also highlights the important progress made in treating and preventing this devastating neurological disease and prioritizes important areas for future research.
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Affiliation(s)
- Tory P Johnson
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA
| | - James Sejvar
- Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30329-4027, USA
| | - Thomas B Nutman
- Helminth Immunology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Avindra Nath
- Section of Infections of the Nervous System, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA;
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10
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Smith ME, Bilal S, Lakwo TL, Habomugisha P, Tukahebwa E, Byamukama E, Katabarwa MN, Richards FO, Cupp EW, Unnasch TR, Michael E. Accelerating river blindness elimination by supplementing MDA with a vegetation "slash and clear" vector control strategy: a data-driven modeling analysis. Sci Rep 2019; 9:15274. [PMID: 31649285 PMCID: PMC6813336 DOI: 10.1038/s41598-019-51835-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 10/09/2019] [Indexed: 01/08/2023] Open
Abstract
Attention is increasingly focusing on how best to accelerate progress toward meeting the WHO's 2030 goals for neglected tropical diseases (NTDs). For river blindness, a major NTD targeted for elimination, there is a long history of using vector control to suppress transmission, but traditional larvicide-based approaches are limited in their utility. One innovative and sustainable approach, "slash and clear", involves clearing vegetation from breeding areas, and recent field trials indicate that this technique very effectively reduces the biting density of Simulium damnosum s.s. In this study, we use a Bayesian data-driven mathematical modeling approach to investigate the potential impact of this intervention on human onchocerciasis infection. We developed a novel "slash and clear" model describing the effect of the intervention on seasonal black fly biting rates and coupled this with our population dynamics model of Onchocerca volvulus transmission. Our results indicate that supplementing annual drug treatments with "slash and clear" can significantly accelerate the achievement of onchocerciasis elimination. The efficacy of the intervention is not very sensitive to the timing of implementation, and the impact is meaningful even if vegetation is cleared only once per year. As such, this community-driven technique will represent an important option for achieving and sustaining O. volvulus elimination.
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Affiliation(s)
- Morgan E Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Shakir Bilal
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Thomson L Lakwo
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | | | | | | | | | - Eddie W Cupp
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
| | - Thomas R Unnasch
- Department of Global Health, College of Public Health, University of South Florida, Tampa, FL, USA
| | - Edwin Michael
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA.
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11
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Cupp E, Sauerbrey M, Cama V, Eberhard M, Lammie PJ, Unnasch TR. Elimination of onchocerciasis in Africa by 2025: the need for a broad perspective. Infect Dis Poverty 2019; 8:50. [PMID: 31303176 PMCID: PMC6628485 DOI: 10.1186/s40249-019-0557-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 05/28/2019] [Indexed: 12/16/2022] Open
Abstract
Background In response to the recent publication “Is onchocerciasis elimination in Africa feasible by 2025: a perspective based on lessons learnt from the African control programmes” by Dadzie et al., it is important to clarify and highlight the positive and unequivocal research and operational contributions from the American experience towards the worldwide elimination of human onchocerciasis (river blindness). Main text The strategies of twice or more rounds of mass drug administration (MDA) of ivermectin per year, as well as the use of OV-16 serology have allowed four American countries to be verified by World Health Organization to have eliminated transmission of Onchocerca volvulus, the etiological agent. These advances were also implemented in Sudan and Uganda; currently, both are the only African countries where ivermectin MDA was safely stopped in several transmission zones. Conclusions Programmatic treatment and evaluation approaches, pioneered in the Americas, are the most efficient among the existing tools for elimination, and their broader use could catalyze the successful elimination of this disease in Africa. Electronic supplementary material The online version of this article (10.1186/s40249-019-0557-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ed Cupp
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, 36849, USA
| | - Mauricio Sauerbrey
- Onchocerciasis Elimination Program for the Americas, 14 Calle 3-51 Zona 10, Edificio Murano Center, Oficina, 1401, Guatemala City, Guatemala
| | - Vitaliano Cama
- Centers for Disease Control and Prevention, 1600 Clifton Rd, MS D-65, Atlanta, GA, 30329, USA
| | - Mark Eberhard
- Centers for Disease Control and Prevention, 1600 Clifton Rd, MS D-65, Atlanta, GA, 30329, USA
| | - Patrick J Lammie
- Task Force for Global Health, 330 W. Ponce de Leon Ave, Decatur, GA, 30030, USA
| | - Thomas R Unnasch
- Center for Global Health Infectious Diseases, University of South Florida College of Public Health, 3720 Spectrum Blvd, Suite 304, Tampa, FL, 33612, USA.
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12
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Hotterbeekx A, Namale Ssonko V, Oyet W, Lakwo T, Idro R. Neurological manifestations in Onchocerca volvulus infection: A review. Brain Res Bull 2018; 145:39-44. [PMID: 30458251 PMCID: PMC6382410 DOI: 10.1016/j.brainresbull.2018.08.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 08/22/2018] [Accepted: 08/25/2018] [Indexed: 11/17/2022]
Abstract
Human onchocerciasis, caused by infection by the filarial nematode Onchocerca volvulus, is a major neglected public health problem that affects millions of people in the endemic regions of sub-Saharan Africa and Latin America. Onchocerciasis is known to be associated with skin and eye disease and more recently, neurological features have been recognized as a major manifestation. Especially the latter poses a severe burden on affected individuals and their families. Although definite studies are awaited, preliminary evidence suggests that neurological disease may include the nodding syndrome, Nakalanga syndrome and epilepsy but to date, the exact pathophysiological mechanisms remain unclear. Currently, the only way to prevent Onchocera volvulus associated disease is through interventions that target the elimination of onchocerciasis through community distribution of ivermectin and larviciding the breeding sites of the Similium or blackfly vector in rivers. In this review, we discuss the epidemiology, potential pathological mechanisms as well as prevention and treatment strategies of onchocerciasis, focusing on the neurological disease.
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Affiliation(s)
- An Hotterbeekx
- University of Antwerp, Global Health Institute, Antwerp, Belgium
| | | | | | - Thomson Lakwo
- Ministry of Health, Division of Vector Control, Kampala, Uganda
| | - Richard Idro
- Makerere University College of Health Sciences, Kampala, Uganda; Centre for Tropical Neuroscience, Kampala, Uganda; University of Oxford, Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, Oxford, UK.
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13
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Murdoch ME. Onchodermatitis: Where Are We Now? Trop Med Infect Dis 2018; 3:E94. [PMID: 30274490 PMCID: PMC6160948 DOI: 10.3390/tropicalmed3030094] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 08/27/2018] [Accepted: 08/28/2018] [Indexed: 02/07/2023] Open
Abstract
Onchocerciasis causes debilitating pruritus and rashes as well as visual impairment and blindness. Prior to control measures, eye disease was particularly prominent in savanna areas of sub-Saharan Africa whilst skin disease was more common across rainforest regions of tropical Africa. Mass drug distribution with ivermectin is changing the global scene of onchocerciasis. There has been successful progressive elimination in Central and Southern American countries and the World Health Organization has set a target for elimination in Africa of 2025. This literature review was conducted to examine progress regarding onchocercal skin disease. PubMed searches were performed using keywords 'onchocerciasis', 'onchodermatitis' and 'onchocercal skin disease' over the past eight years. Articles in English, or with an English abstract, were assessed for relevance, including any pertinent references within the articles. Recent progress in awareness of, understanding and treatment of onchocercal skin disease is reviewed with particular emphasis on publications within the past five years. The global burden of onchodermatitis is progressively reducing and is no longer seen in children in many formerly endemic foci.
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Affiliation(s)
- Michele E Murdoch
- Department of Dermatology, West Herts Hospitals NHS Trust, Vicarage Road, Watford, Hertfordshire WD18 0HB, UK.
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14
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Richards FO, Katabarwa M, Bekele F, Tadesse Z, Mohammed A, Sauerbrey M, Dominguez-Vazquez A, Rodriguez-Perez MA, Fernández-Santos NA, Rizzo N, Schuler Martínez HR, Lovato Silva R, Morales Monroy Z, Habomugisha P, Oguttu DW, Zarroug IMA, Aziz NA, Unnasch TR. Operational Performance of the Onchocerca volvulus "OEPA" Ov16 ELISA Serological Assay in Mapping, Guiding Decisions to Stop Mass Drug Administration, and Posttreatment Surveillance Surveys. Am J Trop Med Hyg 2018; 99:749-752. [PMID: 30014821 DOI: 10.4269/ajtmh.18-0341] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Onchocerciasis is a neglected tropical disease targeted for elimination. The World Health Organization (WHO) has developed guidelines for the verification of onchocerciasis elimination that include entomological and epidemiological criteria. The latter require demonstrating with statistical confidence that the infection prevalence in children is less than 0.1%, necessitating an assay with a high degree of specificity. We present an analysis of the performance of the Onchocerciasis Elimination Program for the Americas (OEPA) version of the Ov16 enzyme-linked immunosorbant assay (ELISA) when used under operational conditions. In Africa and Latin America, the assay demonstrated 99.98% specificity in 69,888 children in 20 foci where transmission was believed to be interrupted. The assay produced a prevalence estimate equal to that of skin snip microscopy when applied in putatively hypo-endemic zones of Ethiopia. The OEPA Ov16 ELISA demonstrated the specificity required to be effectively deployed to verify transmission elimination under the WHO guidelines, while exhibiting a sensitivity equivalent to skin snip microscopy to identify hypo-endemic areas.
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Affiliation(s)
| | | | | | | | | | - Mauricio Sauerbrey
- Onchocerciasis Elimination Program for the Americas, Guatemala City, Guatemala
| | | | | | | | - Nidia Rizzo
- Centro de Estudios en Salud of the Universidad del Valle de, Guatemala (UVG), Guatemala City, Guatemala
| | | | | | | | | | - David W Oguttu
- NTD Control Program, Vector Control Division, Kampala, Uganda
| | | | | | - Thomas R Unnasch
- Center for Global Health Infectious Disease Research, The University of South Florida, Tampa, Florida
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15
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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] [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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16
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Hendy A, Krüger A, Pfarr K, De Witte J, Kibweja A, Mwingira U, Dujardin JC, Post R, Colebunders R, O’Neill S, Kalinga A. The blackfly vectors and transmission of Onchocerca volvulus in Mahenge, south eastern Tanzania. Acta Trop 2018; 181:50-59. [PMID: 29410302 DOI: 10.1016/j.actatropica.2018.01.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 12/15/2017] [Accepted: 01/19/2018] [Indexed: 10/18/2022]
Abstract
The Mahenge Mountains onchocerciasis focus in south eastern Tanzania was historically one of the most heavily infected areas in the country. The vectors of Onchocerca volvulus are mainly Simulium damnosum complex blackflies, but a species of the Simulium neavei group may also contribute to transmission in some areas. The only detailed studies of parasite transmission in Mahenge were conducted in the late 1960s. The taxonomy of the S. damnosum complex has since been revised and onchocerciasis control through annual community directed treatment with ivermectin (CDTI) commenced in 1997. This study aimed to provide a cytogenetic and molecular update of the S. damnosum complex cytoforms present in Mahenge, and to evaluate the current status of O. volvulus transmission by blackflies following 19 years of annual CDTI. Rivers were surveyed to identify sites of S. damnosum s.l. breeding among the eastern slopes of the mountains, and human landing collections of adult female blackflies were made close to breeding sites. Identification of S. damnosum complex cytoforms was by cytotaxonomy of late-instar larvae and ITS1 amplicon size polymorphisms of larvae and adults. Adult blackflies were pool screened for O. volvulus infection using a triplex real-time PCR. The cytoforms 'Nkusi', Simulium kilibanum and 'Turiani' were found breeding in perennial rivers. 'Nkusi' and S. kilibanum were collected on human bait at 7/7 catch sites and possessed ITS1 profiles most closely resembling the molecular forms 'Nkusi J' and S. kilibanum 'T'. Whereas 'Turiani' was present in rivers, it was not collected on human bait and appears to be zoophilic. Simulium nyasalandicum was collected in low numbers on human bait at 3/7 catch sites. In total, 12,452 S. damnosum s.l. were pool screened and O. volvulus infection was detected in 97/104 pools of bodies and 51/104 pools of heads. The estimated percentage of S. damnosum s.l. carrying infective L3 stage parasites was 0.57% (95% CI 0.43%-0.74%). Onchocerca volvulus transmission by S. damnosum s.l. is continuing in the Mahenge Mountains after 19 years of annual CDTI. Infection rates appear similar to those reported in the 1960s, but a more detailed study is required to fully understand the epidemiological significance of the ongoing transmission. These results provide further evidence that annual CDTI may be insufficient to eliminate the parasite in formerly hyperendemic foci.
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17
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Colebunders R, Basáñez MG, Siling K, Post RJ, Rotsaert A, Mmbando B, Suykerbuyk P, Hopkins A. From river blindness control to elimination: bridge over troubled water. Infect Dis Poverty 2018; 7:21. [PMID: 29587844 PMCID: PMC5872540 DOI: 10.1186/s40249-018-0406-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 03/12/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND An estimated 25 million people are currently infected with onchocerciasis (a parasitic infection caused by the filarial nematode Onchocerca volvulus and transmitted by Simulium vectors), and 99% of these are in sub-Saharan Africa. The African Programme for Onchocerciasis Control closed in December 2015 and the World Health Organization has established a new structure, the Expanded Special Project for the Elimination of Neglected Tropical Diseases for the coordination of technical support for activities focused on five neglected tropical diseases in Africa, including onchocerciasis elimination. AIMS In this paper we argue that despite the delineation of a reasonably well-defined elimination strategy, its implementation will present particular difficulties in practice. We aim to highlight these in an attempt to ensure that they are well understood and that effective plans can be laid to solve them by the countries concerned and their international partners. CONCLUSIONS A specific concern is the burden of disease caused by onchocerciasis-associated epilepsy in hyperendemic zones situated in countries experiencing difficulties in strengthening their onchocerciasis control programmes. These difficulties should be identified and programmes supported during the transition from morbidity control to interruption of transmission and elimination.
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Affiliation(s)
| | - Maria-Gloria Basáñez
- London Centre for Neglected Tropical Disease Research, Imperial College London, London, UK
| | - Katja Siling
- Institute of Tropical Medicine, Antwerp, Belgium
- London School of Hygiene & Tropical Medicine, London, UK
| | - Rory J. Post
- London School of Hygiene & Tropical Medicine, London, UK
- Liverpool John Moores University, Liverpool, UK
| | - Anke Rotsaert
- Global Health Institute, University of Antwerp, Antwerp, Belgium
| | - Bruno Mmbando
- National Institute for Medical Research, Tanga, Tanzania
| | | | - Adrian Hopkins
- Neglected and Disabling diseases of Poverty Consultant, Gravesend, Kent, UK
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18
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Elhassan E, Zhang Y, Bush S, Molyneux D, Kollmann MKH, Sodahlon Y, Richards F. The role of the NGDO Coordination Group for the Elimination of Onchocerciasis. Int Health 2018; 10:i97-i101. [PMID: 29471339 DOI: 10.1093/inthealth/ihx050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 11/30/2017] [Indexed: 11/14/2022] Open
Abstract
The NGDO Coordination Group for the Control of Onchocerciasis was launched in 1992, and with the paradigm shift from control of disease to elimination of onchocerciasis transmission, the Group shifted its orientation to that new paradigm in 2013. It also changed its name, replacing 'control' with 'elimination.' In doing so, the Group has repositioned itself to build on the successes of the past to finish the job it began over 25 years ago.
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Affiliation(s)
| | | | | | - David Molyneux
- Liverpool School of Tropical Medicine and Hygiene, Liverpool, UK
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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] [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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20
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Boussinesq M, Fobi G, Kuesel AC. Alternative treatment strategies to accelerate the elimination of onchocerciasis. Int Health 2018; 10:i40-i48. [PMID: 29471342 PMCID: PMC5881258 DOI: 10.1093/inthealth/ihx054] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 10/30/2017] [Accepted: 11/14/2017] [Indexed: 02/06/2023] Open
Abstract
The use of alternative (or complementary) treatment strategies (ATSs) i.e. differing from annual community-directed treatment with ivermectin (CDTI) is required in some African foci to eliminate onchocerciasis by 2025. ATSs include vector control, biannual or pluriannual CDTI, better timing of CDTI, community-directed treatment with combinations of currently available anthelminthics or new drugs, and 'test-and-treat' (TNT) strategies requiring diagnosis of infection and/or contraindications to treatment for decisions on who to treat with what regimen. Two TNT strategies can be considered. Loa-first TNT, designed for loiasis-endemic areas and currently being evaluated using a rapid test (LoaScope), consists of identifying individuals with levels of Loa microfilaremia associated with a risk of post-ivermectin severe adverse events to exclude them from ivermectin treatment and in treating the rest (usually >97%) of the population safely. Oncho-first TNT consists of testing community members for onchocerciasis before giving treatment (currently ivermectin or doxycycline) to those who are infected. The choice of the ATS depends on the prevalences and intensities of infection with Onchocerca volvulus and Loa loa and on the relative cost-effectiveness of the strategies for the given epidemiological situation. Modelling can help select the optimal strategies, but field evaluations to determine the relative cost-effectiveness are urgently needed.
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Affiliation(s)
- Michel Boussinesq
- IRD UMI 233-INSERM U1175-Montpellier University, 34394 Montpellier, France
| | - Grace Fobi
- African Programme for Onchocerciasis Control, Ouagadougou, Burkina Faso
| | - Annette C Kuesel
- UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, Geneva, Switzerland
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21
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Cano J, Basáñez MG, O'Hanlon SJ, Tekle AH, Wanji S, Zouré HG, Rebollo MP, Pullan RL. Identifying co-endemic areas for major filarial infections in sub-Saharan Africa: seeking synergies and preventing severe adverse events during mass drug administration campaigns. Parasit Vectors 2018; 11:70. [PMID: 29382363 PMCID: PMC5791223 DOI: 10.1186/s13071-018-2655-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 01/16/2018] [Indexed: 02/06/2023] Open
Abstract
Background Onchocerciasis and lymphatic filariasis (LF) are major filarial infections targeted for elimination in most endemic sub-Saharan Africa (SSA) countries by 2020/2025. The current control strategies are built upon community-directed mass administration of ivermectin (CDTI) for onchocerciasis, and ivermectin plus albendazole for LF, with evidence pointing towards the potential for novel drug regimens. When distributing microfilaricides however, considerable care is needed to minimise the risk of severe adverse events (SAEs) in areas that are co-endemic for onchocerciasis or LF and loiasis. This work aims to combine previously published predictive risk maps for onchocerciasis, LF and loiasis to (i) explore the scale of spatial heterogeneity in co-distributions, (ii) delineate target populations for different treatment strategies, and (iii) quantify populations at risk of SAEs across the continent. Methods Geographical co-endemicity of filarial infections prior to the implementation of large-scale mass treatment interventions was analysed by combining a contemporary LF endemicity map with predictive prevalence maps of onchocerciasis and loiasis. Potential treatment strategies were geographically delineated according to the level of co-endemicity and estimated transmission intensity. Results In total, an estimated 251 million people live in areas of LF and/or onchocerciasis transmission in SSA, based on 2015 population estimates. Of these, 96 million live in areas co-endemic for both LF and onchocerciasis, providing opportunities for integrated control programmes, and 83 million live in LF-monoendemic areas potentially targetable for the novel ivermectin-diethylcarbamazine-albendazole (IDA) triple therapy. Only 4% of the at-risk population live in areas co-endemic with high loiasis transmission, representing up to 1.2 million individuals at high risk of experiencing SAEs if treated with ivermectin. In these areas, alternative treatment strategies should be explored, including biannual albendazole monotherapy for LF (1.4 million individuals) and ‘test-and-treat’ strategies (8.7 million individuals) for onchocerciasis. Conclusions These maps are intended to initiate discussion around the potential for tailored treatment strategies, and highlight populations at risk of SAEs. Further work is required to test and refine strategies in programmatic settings, providing the empirical evidence needed to guide efforts towards the 2020/2025 goals and beyond. Electronic supplementary material The online version of this article (10.1186/s13071-018-2655-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jorge Cano
- Department of Disease Control, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK.
| | - Maria-Gloria Basáñez
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary's campus), Imperial College London, London, UK
| | - Simon J O'Hanlon
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary's campus), Imperial College London, London, UK
| | - Afework H Tekle
- Research Foundation in Tropical Medicine and the Environment, Buea, Cameroon
| | - Samuel Wanji
- Department of Biochemistry and Microbiology, University of Buea, P.O. Box 63, Buea, Cameroon.,Research Foundation in Tropical Medicine and the Environment, Buea, Cameroon
| | - Honorat G Zouré
- Former African Programme for Onchocerciasis Control Programme, Ouagadougou, Burkina Faso
| | - Maria P Rebollo
- Expanded Special Programme for Elimination of Neglected Tropical Diseases (ESPEN), Brazzaville, Republic of Congo
| | - Rachel L Pullan
- Department of Disease Control, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
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22
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Luroni LT, Gabriel M, Tukahebwa E, Onapa AW, Tinkitina B, Tukesiga E, Nyaraga M, Auma AM, Habomugisha P, Byamukama E, Oguttu D, Katabarwa M, Unnasch TR. The interruption of Onchocerca volvulus and Wuchereria bancrofti transmission by integrated chemotherapy in the Obongi focus, North Western Uganda. PLoS One 2017; 12:e0189306. [PMID: 29253862 PMCID: PMC5734780 DOI: 10.1371/journal.pone.0189306] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 11/22/2017] [Indexed: 11/18/2022] Open
Abstract
Intervention Few studies have documented the interruption of onchocerciasis and Lymphatic Filariasis (LF) by integrated chemotherapy in Uganda. The study describes the interruption of transmission of the two diseases co-endemic in Obongi focus, north western Uganda. Base line data for Onchocerciasis and LF were collected in 1994 and 2006, respectively. Annual mass drug administration for onchocerciasis (Ivermectin) and Lymphatic Filariasis (Ivermectin + albendazole) was conducted for 20 and 6 years, respectively. Thereafter, assessments by skin snip, larval searches in rivers and human landing catches were performed. Children <10 years were screened for IgG4 antibodies using Ov16 ELISA technique in 2013. LF Pre-TAS and TAS1 were conducted in sentinel sites. ITN coverage and utilization for the implementation unit was also reported. Intervention coverage Onchocerciasis treatment coverage was <80% but improved with the introduction of CDTI in 1999. While for LF, effective coverage of >65% was achieved in the six treatment rounds. Household ownership of ITN’s and utilization was 96% and 72.4%., respectively. Impact Parasitological examinations conducted for onchocerciasis among 807 adults and children, revealed a reduction in mf prevalence from 58% in 1994 to 0% in 2012. Entomological monitoring conducted at the two sites had no single Simulium damnosum fly caught. Serological analysis using Ov16 ELISA for onchocerciasis revealed that out of the 3,308 children <10 years old screened in 2013, only 3/3308 (0.091%) positive cases were detected. All Ov16 positive children were negative when tested for patent infection by skin snip PCR. A reduction in LF microfilaria prevalence from 2.5% (n = 13/522) in 2006 to 0.0% (n = 602) in 2014 was observed. LF TAS1 conducted in 2015 among 1,532 children 6–7 years, all were negative for antigens of W. bancrofti. Conclusion The results concluded that interruption of onchocerciasis and LF has been achieved.
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Affiliation(s)
| | - Matwale Gabriel
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | | | | | | | - Michael Nyaraga
- Moyo District Local Government, Medical Department, Moyo, Uganda
| | - Anna Mary Auma
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | | | - David Oguttu
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | - Thomas Raymond Unnasch
- University of South Florida, Global Health Infectious Disease Research, College of Public Health, Tampa, FL, United States of America
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Loum D, Katholi CR, Lakwo T, Habomugisha P, Tukahebwa EM, Unnasch TR. Evaluation of Community-Directed Operation of Black Fly Traps for Entomological Surveillance of Onchocerca volvulus Transmission in the Madi-Mid North Focus of Onchocerciasis in Northern Uganda. Am J Trop Med Hyg 2017; 97:1235-1242. [PMID: 29031285 DOI: 10.4269/ajtmh.17-0244] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Entomological measures of transmission are important metrics specified by the World Health Organization to document the suppression and interruption of transmission of Onchocerca volvulus, the causative agent of onchocerciasis. These metrics require testing of large numbers of vector black flies. Black fly collection has relied on human landing collections, which are inefficient and potentially hazardous. As the focus of the international community has shifted from onchocerciasis control to elimination, replacement of human landing collections has become a priority. The Esperanza window trap (EWT) has shown promise as an alternative method for collection of Simulium damnosum s.l., the primary vector of O. volvulus in Africa. Here, we report the results of a community-based trial of the EWT in northern Uganda. Traps operated by residents were compared with human landing collections in two communities over 5 months. Three traps, when operated by a single village resident, collected over four times as many S. damnosum as did the two-men collection team. No significant differences were noted among the bait formulations. The results suggest that EWTs may be effectively operated by community residents and that the trap represents a viable alternative to human landing collections for entomological surveillance of O. volvulus transmission.
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Affiliation(s)
- Denis Loum
- Nwoya District Local Government, Nwoya, Uganda
| | - Charles R Katholi
- Department of Biostatistics, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama
| | - Thomson Lakwo
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | | | - Thomas R Unnasch
- Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
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Kelly-Hope L, Paulo R, Thomas B, Brito M, Unnasch TR, Molyneux D. Loa loa vectors Chrysops spp.: perspectives on research, distribution, bionomics, and implications for elimination of lymphatic filariasis and onchocerciasis. Parasit Vectors 2017; 10:172. [PMID: 28381279 PMCID: PMC5382514 DOI: 10.1186/s13071-017-2103-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 03/23/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Loiasis is a filarial disease caused Loa loa. The main vectors are Chrysops silacea and C. dimidiata which are confined to the tropical rainforests of Central and West Africa. Loiasis is a mild disease, but individuals with high microfilaria loads may suffer from severe adverse events if treated with ivermectin during mass drug administration campaigns for the elimination of lymphatic filariasis and onchocerciasis. This poses significant challenges for elimination programmes and alternative interventions are required in L. loa co-endemic areas. The control of Chrysops has not been considered as a viable cost-effective intervention; we reviewed the current knowledge of Chrysops vectors to assess the potential for control as well as identified areas for future research. RESULTS We identified 89 primary published documents on the two main L. loa vectors C. silacea and C dimidiata. These were collated into a database summarising the publication, field and laboratory procedures, species distributions, ecology, habitats and methods of vector control. The majority of articles were from the 1950-1960s. Field studies conducted in Cameroon, Democratic Republic of Congo, Equatorial Guinea, Nigeria and Sudan highlighted that C. silacea is the most important and widespread vector. This species breeds in muddy streams or swampy areas of forests or plantations, descends from forest canopies to feed on humans during the day, is more readily adapted to human dwellings and attracted to wood fires. Main vector targeted measures proposed to impact on L. loa transmission included personal repellents, household screening, indoor residual spraying, community-based environmental management, adulticiding and larviciding. CONCLUSIONS This is the first comprehensive review of the major L. loa vectors for several decades. It highlights key vector transmission characteristics that may be targeted for vector control providing insights into the potential for integrated vector management, with multiple diseases being targeted simultaneously, with shared human and financial resources and multiple impact. Integrated vector management programmes for filarial infections, especially in low transmission areas of onchocerciasis, require innovative approaches and alternative strategies if the elimination targets established by the World Health Organization are to be achieved.
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Affiliation(s)
- Louise Kelly-Hope
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Rossely Paulo
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.,CISA, Health Research Centre of Angola, Caxito, Angola
| | - Brent Thomas
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Miguel Brito
- CISA, Health Research Centre of Angola, Caxito, Angola.,Lisbon School of Health Technology, Lisbon, Portugal
| | - Thomas R Unnasch
- College of Public Health, Department of Global Health, University of South Florida, Tampa, USA
| | - David Molyneux
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK
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Cheke RA. Factors affecting onchocerciasis transmission: lessons for infection control. Expert Rev Anti Infect Ther 2017; 15:377-386. [PMID: 28117596 DOI: 10.1080/14787210.2017.1286980] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Onchocerca volvulus infects in excess of 15 million people. The vectors are Simulium blackflies, varieties of which differ in their ecologies, behavior and vectorial abilities. Control of the vectors and mass administrations of ivermectin have succeeded in reducing prevalences with elimination achieved in some foci, particularly in Central and southern America. In Africa, progress towards elimination has been less successful. Areas covered: Even with community directed treatment with ivermectin (CDTI), control has been difficult in African areas with initial prevalences in excess of 55%, especially if only annual treatments are dispensed. This is partly attributable to insufficient coverage, but the appearance of incipiently resistant non-responding parasites and lack of attention to vector biology in modeling and planning outcomes of intervention programmes have also played their parts, with recrudescence now appearing in some treated areas. Expert commentary: The biology of onchocerciasis is complex involving different vectors with differing abilities to transmit parasites, diverse pathologies related to geographical and parasite variations and endosymbionts in both parasite and vector. Modeling to predict epidemiological and control outcomes is addressing this complexity but more attention needs to be given to the vectors' roles to further understanding of where and when control measures will succeed.
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Affiliation(s)
- Robert A Cheke
- a Agriculture, Health and Environment Department, Natural Resources Institute , University of Greenwich at Medway , Kent , UK.,b Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary's campus) , Imperial College London , London , UK
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