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Máquina M, Opiyo MA, Cuamba N, Marrenjo D, Rodrigues M, Armando S, Nhate S, Luis F, Saúte F, Candrinho B, Lobo NF, Paaijmans KP. Multiple Anopheles species complicate downstream analysis and decision-making in a malaria pre-elimination area in southern Mozambique. Malar J 2024; 23:23. [PMID: 38238774 PMCID: PMC10797956 DOI: 10.1186/s12936-024-04842-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 01/05/2024] [Indexed: 01/22/2024] Open
Abstract
BACKGROUND Different anopheline species (even within a species group/complex) can differ in their feeding and resting behaviours, which impact both malaria transmission patterns as well as the efficacy of vector control interventions. While morphological identification of sampled specimens is an important first step towards understanding species diversity and abundance, misidentification can result in the implementation of less effective vector control measures, and consequently smaller reductions in the number of local malaria cases. Focusing on southern Mozambique, a malaria pre-elimination area where malaria remains persistent, the aims of this preliminary study were to use molecular identification (CO1 and ITS2 barcoding) to (1) validate the results from the morphological identification (with a particular focus on Anopheles pharoensis and Anopheles squamosus), and (2) have a closer look at the Anopheles coustani group (which includes Anopheles tenebrosus and Anopheles ziemanni). METHODS Female anopheline mosquitoes (n = 81) were identified morphologically and subsequently sequenced at the ribosomal DNA internal transcribed spacer region 2 (ITS2) and/or cytochrome oxidase subunit 1 (CO1) loci towards species determination. RESULTS Out of the 62 specimens that were identified morphologically to species, 4 (6.5%) were misidentified. Regarding the An. coustani group, morphological identification showed that several members are present in southern Mozambique, including An. coustani sensu lato (s.l.), An. ziemanni and An. tenebrosus. However, based on both ITS2 and CO1 sequences, the exact species remains unknown for the latter two members until voucher sequences are available for comparison. CONCLUSION The reason(s) for morphological misidentification of anopheline mosquitoes need to be mitigated. This is usually related to both the capacity (i.e. training) of the microscopist to identify anopheline species, and the information provided in the dichotomous identification key. As the An. coustani complex contributes to (residual) malaria transmission in sub-Saharan Africa, it may play a role in the observed persistent malaria in southern Mozambique. A better baseline characterizing of the local anophelines species diversity and behaviours will allow us to improve entomological surveillance strategies, better understand the impact of vector control on each local vector species, and identify new approaches to target those vector species.
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Affiliation(s)
- Mara Máquina
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Manhica, Mozambique
| | - Mercy A Opiyo
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Manhica, Mozambique
- ISGlobal, Barcelona, Spain
- Malaria Elimination Initiative, University of California San Francisco, San Francisco, CA, USA
| | - Nelson Cuamba
- Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique
- PMI VectorLink Project, Abt Associates Inc., Maputo, Mozambique
| | - Dulcisária Marrenjo
- Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique
| | | | | | - Sheila Nhate
- Maputo Provincial Health Service, Matola, Mozambique
| | - Fabião Luis
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Manhica, Mozambique
| | - Francisco Saúte
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Manhica, Mozambique
| | - Baltazar Candrinho
- Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique
| | - Neil F Lobo
- Malaria Elimination Initiative, University of California San Francisco, San Francisco, CA, USA
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Krijn P Paaijmans
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Manhica, Mozambique.
- ISGlobal, Barcelona, Spain.
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, AZ, USA.
- Simon A. Levin Mathematical, Computational and Modeling Sciences Center, Arizona State University, Tempe, AZ, USA.
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Kuetche MTC, Tabue RN, Fokoua-Maxime CD, Evouna AM, Billong S, Kakesa O. Prevalence and risk factors determinants of the non-use of insecticide-treated nets in an endemic area for malaria: analysis of data from Cameroon. Malar J 2023; 22:205. [PMID: 37407962 DOI: 10.1186/s12936-023-04510-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 02/21/2023] [Indexed: 07/07/2023] Open
Abstract
BACKGROUND Malaria is the main cause of morbidity and mortality in Cameroon. Insecticide-treated nets (ITNs) significantly reduce malaria transmission, but their use is not common in the population. This study aimed to estimate the nationwide prevalence of the non-use of ITNs and identify its major determinants. METHODS A cross-sectional study was conducted on interview data collected in households selected across all the regions of Cameroon through a non-probabilistic, random, 2-stage stratified sampling process. Descriptive statistics were used to describe the distribution of baseline characteristics across the households, and statistical tests assessed if the distribution of these characteristics differed significantly based on the non-use of ITNs, with 0.05 serving as a threshold of the p-value for statistical significance. The prevalence of the non-use of ITNs was estimated, and logistic regression models were used to tally the odds ratios of the associations between various factors and the non-use of ITNs, along with their 95% confidence intervals. The sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve (AUC) were determined, and the Hosmer Lemeshow test was used to measure the goodness of fit of each statistical model. RESULTS Of the 7593 households interviewed, 77% had at least one ITN and 59% of the population used ITNs. Only 72% of the population with at least one ITN used it. The logistic model of the multivariate analysis was significant at a 5% threshold. The AUC was 0.7087 and the error rate was 18.01%. The sensitivity and specificity of the model were 97.56% and 13.70%, respectively. The factors that were associated with ITN use were the presence of sufficient nets in the household (p < 0.0001), the region of residence (p < 0.0001), the level of education of the respondent (p < 0.0001), and the standard of living (p = 0.0286). Sex, age, colour preferences, as well as the shape and size of the nets were not associated with ITN use. CONCLUSIONS The use of ITNs in Cameroon was low and varied according to specific factors. These identified factors could be used as the foundations of effective sensitization campaigns on the importance of ITNs.
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Affiliation(s)
| | | | - C D Fokoua-Maxime
- School of Public Health, New York State University at Albany, Albany, NY, USA
| | - Armel M Evouna
- Cameroon Field Epidemiology Training Program, Yaoundé, Cameroon
| | - Serge Billong
- National Committee Against HIV-AIDS, Yaoundé, Cameroon
| | - Olivier Kakesa
- President's Malaria Initiative (PMI)-Measure Malaria Project, Yaoundé, Cameroon
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Kampango A, Pinto J, Abílio AP, Machoe E, Matusse J, McCall PJ. Characterisation of human exposure to nocturnal biting by malaria and arbovirus vectors in a rural community in Chókwè district, southern Mozambique. Wellcome Open Res 2023; 8:193. [PMID: 37484481 PMCID: PMC10357080 DOI: 10.12688/wellcomeopenres.19278.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2023] [Indexed: 07/25/2023] Open
Abstract
Background: Understanding the magnitude of human exposure to mosquito biting is fundamental to reduce pathogen transmission. Here we report on a study quantifying the levels of mosquitoes attacking humans throughout the night in a rural area of Southern Mozambique. Methods: Surveys were carried out in Massavasse village, southern Mozambique. The abundance and composition of host-seeking mosquito communities at night were assessed by human-landing catches (HLC) at one-hour intervals. Periods when people were located predominantly outdoors or indoors were used to estimate the amount of residents' exposure to mosquito bites in either location, to explore the potential impact a bed net could have had in reducing biting by each vector species. Results: A total of 69,758 host-seeking female mosquitoes comprising 23 species in four genera were collected. The exposure to biting by virtually all vector species was consistently high outdoors, typically at early evening and morning, with exception of An. gambiae s.l which was likely of biting a person with nearly same intensity indoors and outdoors throughout the night. Bed nets use could have reduced biting by An. gambiae s.l (dominated by An. arabiensis), Ma. africana, Ma. uniformis, Cx. pipiens, Cx. antennatus, and Cx. poicilipes by 53%, 47%, 46%, 38%, 31%, and 28% respectively, compared to non-users. Conversely, a bed net user would have had little protection against An. pharoensis, An. ziemanni, An. tenebrosus, and Cx. tritaeniorhynchus biting exposures. Conclusions: This study showed that Massavasse residents were exposed to high levels of outdoor biting by malaria and arbovirus vectors that abound in the village. The findings help to identify entomological drivers of persistent malaria transmission in Mozambique and identify a wide range of arbovirus vectors nocturnally active in rural areas, many with outbreak potential. The study highlights the need for a surveillance system for monitoring arboviral diseases vectors in Mozambique.
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Affiliation(s)
- Ayubo Kampango
- Sector de Estudo de Vectores, Instituto Nacional de Saúde (INS), Maputo, Villa de Marracuene EN1, Plot 3943, Mozambique
- Department of Zoology and Entomology, University of Pretoria, Pretoria, Hatfield, 0028, South Africa
| | - João Pinto
- Global Health and Tropical Medicine, Institute of Hygiene and Tropical Medicine (IHMT), Lisbon, Rua da Junqueira, 100 1349-008, Portugal
| | - Ana Paula Abílio
- Sector de Estudo de Vectores, Instituto Nacional de Saúde (INS), Maputo, Villa de Marracuene EN1, Plot 3943, Mozambique
| | - Elias Machoe
- Sector de Estudo de Vectores, Instituto Nacional de Saúde (INS), Maputo, Villa de Marracuene EN1, Plot 3943, Mozambique
| | - Júlio Matusse
- Sector de Estudo de Vectores, Instituto Nacional de Saúde (INS), Maputo, Villa de Marracuene EN1, Plot 3943, Mozambique
| | - Philip J. McCall
- Vector Biology Department, Liverpool School of Tropical Medicine (LSTM), Liverpool, Pembroke Place, L3 5QA, UK
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Atuh NI, Anong DN, Jerome FC, Oriero E, Mohammed NI, D’Alessandro U, Amambua-Ngwa A. High genetic complexity but low relatedness in Plasmodium falciparum infections from Western Savannah Highlands and coastal equatorial Lowlands of Cameroon. Pathog Glob Health 2022; 116:428-437. [PMID: 34308788 PMCID: PMC9518281 DOI: 10.1080/20477724.2021.1953686] [Citation(s) in RCA: 4] [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] [Indexed: 11/06/2022] Open
Abstract
To determine the diversity and connectivity of infections in Northwestern and Southwestern Cameroon, 232 Plasmodium falciparum infections, collected in 2018 from the Ndop Health District (NHD) in the western savannah highlands in the Northwest and the Limbe Health District (LHD) in the coastal lowland forests in the Southwest of Cameroon were genotyped for nine neutral microsatellite markers. Overall infection complexity and genetic diversity was significantly (p < 0.05) lower in NHD than LHD, (Mean MOI = 2.45 vs. 2.97; Fws = 0.42 vs. 0.47; Mean He = 0.84 vs. 0.89, respectively). Multi-locus linkage disequilibrium was generally low but significantly higher in the NHD than LHD population (mean ISA= 0.376 vs 0.093). Consequently, highly related pairs of isolates were observed in NHD (mean IBS = 0.086) compared to those from the LHD (mean IBS = 0.059). Infections from the two regions were mostly unrelated (mean IBS = 0.059), though the overall genetic differentiation across the geographical range was low. Indices of differentiation between the populations were however significant (overall pairwise Fst = 0.048, Jost's D = 0.133, p < 0.01). Despite the high human migration across the 270km separating the study sites, these results suggest significant restrictions to gene flow against contiguous geospatial transmission of malaria in west Cameroon. Clonal infections in the highland sites could be driven by lower levels of malaria prevalence and seasonal transmission. How these differences in genetic diversity and complexity affect responses to interventions such as drugs will require further investigations from broader community sampling.
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Affiliation(s)
- Ngoh Ines Atuh
- Department of Biomedical Science, Faculty of Health Science, University of Buea, Buea, Cameroon
- Disease Control and Elimination, Medical Research Council Unit the Gambia at LSHTM. Banjul, The Gambia
| | - Damian Nota Anong
- Department of Microbiology & Parasitology, Faculty of Science, University of Buea, Molyko Buea, Cameroon
| | - Fru-Cho Jerome
- Department of Biomedical Science, Faculty of Health Science, University of Buea, Buea, Cameroon
| | - Eniyou Oriero
- Disease Control and Elimination, Medical Research Council Unit the Gambia at LSHTM. Banjul, The Gambia
| | - Nuredin Ibrahim Mohammed
- Disease Control and Elimination, Medical Research Council Unit the Gambia at LSHTM. Banjul, The Gambia
| | - Umberto D’Alessandro
- Department of Microbiology & Parasitology, Faculty of Science, University of Buea, Molyko Buea, Cameroon
| | - Alfred Amambua-Ngwa
- Disease Control and Elimination, Medical Research Council Unit the Gambia at LSHTM. Banjul, The Gambia
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Kwi PN, Ewane EE, Moyeh MN, Tangi LN, Ntui VN, Zeukeng F, Sofeu-Feugaing DD, Achidi EA, Cho-Ngwa F, Amambua-Ngwa A, Bigoga JD, Apinjoh TO. Diversity and behavioral activity of Anopheles mosquitoes on the slopes of Mount Cameroon. Parasit Vectors 2022; 15:344. [PMID: 36171589 PMCID: PMC9520907 DOI: 10.1186/s13071-022-05472-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 09/05/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria remains endemic in Cameroon, with heterogeneous transmission related to eco-climatic variations, vector diversity and spatial distribution. The intensification of malaria prevention and control through the free distribution of insecticide-treated nets in recent years may have altered the composition, geographic distribution and natural infection rate of Anopheles species, with implications for malaria transmission dynamics. The present study seeks to assess the vectorial diversity, dynamics and infectivity across different seasons and altitudes in relationship to parasite prevalence around the slopes of Mount Cameroon, southwestern region. METHOD Mosquitoes were sampled (indoors and outdoors) in 11 eco-epidemiological settings at low (18-197 m), intermediate (371-584 m) and high (740-1067 m) altitude by nightly human landing catches. The mosquitoes were identified morphologically and Anopheles gambiae sibling species identified by PCR. Parity status was ascertained by examining the ovaries and the entomological inoculation rates (EIR) determined by Plasmodium falciparum circumsporozoite antigen ELISA of the head-thorax. The prevalence of Plasmodium infection across target communities was assessed using rapid diagnostic tests. RESULTS A total of 7327 (18.0 mosquitoes/trap/night) mosquitoes were trapped, mainly during the rainy season (5678, 77.5%) and at low altitude (3669, 50.1%). Anopheles spp. (5079, 69.3%) was the most abundant genera and An. gambiae complex (2691, 36.7%) the major vector, varying with altitude (χ2 = 183.87, df = 8, P < 0.001) and season (χ2 = 28.14, df = 4, P < 0.001). Only An. gambiae (s.s.) was identified following molecular analysis of An. gambiae complex siblings. The overall biting peak for An. gambiae complex was 2-3 a.m. Anopheles cinctus was the most abundant secondary vector in the area. The average EIR in the area was 2.08 infective bites per person per night (ib/p/n), higher at low (2.45 ib/p/n) than at intermediate altitude (1.39 ib/p/n) and during the rainy (1.76 ib/p/n) compared to the dry season (0.34 ib/p/n). Anopheles funestus was most infectious overall (28.1%, 16/57) while An. gambiae had the highest inoculation rates averaging 1.33 ib/p/n. Most Anopheles species across all altitudes and seasons were parous, highest in communities with the highest proportion of malaria parasite infections. CONCLUSION Anopheles gambiae (s.s.) remains the major malaria vector in the area and An. cinctus possibly a secondary vector of the disease in the slopes of Mt. Cameroon. The seasonal and altitudinal effects on the distribution of these mosquitoes may have implications for the transmission of malaria and its control strategies in the area. Regular monitoring of the bionomics of local Anopheles vector species and targeted control interventions in the 'hotspots' is necessary to curb the prevalence of the infection and incidence of disease.
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Affiliation(s)
- Pilate N Kwi
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
| | - Elvis E Ewane
- Department of Medical Laboratory Sciences, University of Buea, Buea, Cameroon
| | - Marcel N Moyeh
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon.,Department of Chemical and Biological Engineering, The University of Bamenda, Bamenda, Cameroon
| | - Livinus N Tangi
- Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Vincent N Ntui
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
| | - Francis Zeukeng
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon.,Laboratory for Vector Biology and Control, The Biotechnology Centre, University of Yaounde 1, Yaounde, Cameroon
| | | | - Eric A Achidi
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
| | - Fidelis Cho-Ngwa
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon.,Department of Chemical and Biological Engineering, The University of Bamenda, Bamenda, Cameroon
| | - Alfred Amambua-Ngwa
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Jude D Bigoga
- Laboratory for Vector Biology and Control, The Biotechnology Centre, University of Yaounde 1, Yaounde, Cameroon
| | - Tobias O Apinjoh
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon. .,Department of Chemical and Biological Engineering, The University of Bamenda, Bamenda, Cameroon.
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Fernández Montoya L, Martí-Soler H, Máquina M, Comiche K, Cuamba I, Alafo C, Koekemoer LL, Sherrard-Smith E, Bassat Q, Galatas B, Aide P, Cuamba N, Jotamo D, Saúte F, Paaijmans KP. The mosquito vectors that sustained malaria transmission during the Magude project despite the combined deployment of indoor residual spraying, insecticide-treated nets and mass-drug administration. PLoS One 2022; 17:e0271427. [PMID: 36084031 PMCID: PMC9462736 DOI: 10.1371/journal.pone.0271427] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/23/2022] [Indexed: 11/18/2022] Open
Abstract
The "Magude project" aimed but failed to interrupt local malaria transmission in Magude district, southern Mozambique, by using a comprehensive package of interventions, including indoor residual spraying (IRS), pyrethroid-only long-lasting insecticide treated nets (LLINs) and mass-drug administration (MDA). Here we present detailed information on the vector species that sustained malaria transmission, their association with malaria incidence and behaviors, and their amenability to the implemented control interventions. Mosquitoes were collected monthly between May 2015 and October 2017 in six sentinel sites in Magude district, using CDC light traps both indoors and outdoors. Anopheles arabiensis was the main vector during the project, while An. funestus s.s., An. merus, An. parensis and An. squamosus likely played a secondary role. The latter two species have never previously been found positive for Plasmodium falciparum in southern Mozambique. The intervention package successfully reduced vector sporozoite rates in all species throughout the project. IRS was effective in controlling An. funestus s.s. and An. parensis, which virtually disappeared after its first implementation, but less effective at controlling An. arabiensis. Despite suboptimal use, LLINs likely provided significant protection against An. arabiensis and An. merus that sought their host largely indoors when people where in bed. Adding IRS on top of LLINs and MDA likely added value to the control of malaria vectors during the Magude project. Future malaria elimination attempts in the area could benefit from i) increasing the use of LLINs, ii) using longer-lasting IRS products to counteract the increase in vector densities observed towards the end of the high transmission season, and iii) a higher coverage with MDA to reduce the likelihood of human infection. However, additional interventions targeting vectors that survive IRS and LLINs by biting outdoors or indoors before people go to bed, will be likely needed to achieve local malaria elimination.
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Affiliation(s)
- Lucía Fernández Montoya
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | | | - Mara Máquina
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Kiba Comiche
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Inocencia Cuamba
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Celso Alafo
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Lizette L. Koekemoer
- Faculty of Health Sciences, WITS Research Institute for Malaria, University of the Witswatersrand and the Natitonal Institute for Communicable Diseases, Johannesburg, South Africa
| | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Quique Bassat
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
- ICREA, Barcelona, Spain
- Pediatrics Department, Hospital Sant Joan de Déu, Universitat de Barcelona, Esplugues, Barcelona, Spain
- Consorcio de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Beatriz Galatas
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Pedro Aide
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
- Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique
| | - Nelson Cuamba
- Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique
- PMI VectorLink Project, Abt Associates Inc., Maputo, Mozambique
| | - Dulcisaria Jotamo
- Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique
| | - Francisco Saúte
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Krijn P. Paaijmans
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, AZ, United States of America
- The Biodesign Center for Immunotherapy, Vaccines and Virotherapy, Arizona State University, Tempe, AZ, United States of America
- Simon A. Levin Mathematical, Computational and Modeling Sciences Center, Arizona State University, Tempe, AZ, United States of America
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Nlinwe NO, Nchefor FG, Takwi NB. Impact of long lasting insecticidal nets on asymptomatic malaria during pregnancy, in a rural and urban setting in Cameroon. Parasite Epidemiol Control 2022; 18:e00265. [PMID: 35992014 PMCID: PMC9375851 DOI: 10.1016/j.parepi.2022.e00265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 07/04/2022] [Accepted: 08/09/2022] [Indexed: 11/16/2022] Open
Abstract
According to the world malaria report more malaria cases were reported in 2020 than in 2019, due to disruptions in the distribution of insecticide treated nets, caused by the COVID-19 pandemic. Consequently a projected 34.32% (11.6 million out of 33.8 million) pregnancies were exposed to malaria in the WHO African Region in 2020. This study was therefore designed to assess the impact of long lasting insecticidal nets (LLINs) on asymptomatic malaria in the pregnant women attending the Foumbot District Hospital (rural setting) and the Bamenda Regional Hospital (urban setting). This was a hospital based cross-sectional study done within three months from February to April 2021. A structured questionnaire and the CareStart™ Pf Malaria HRP2 qualitative rapid diagnostic test were used for data collection. Data were analysed using descriptive statistics, and Chi-square test. The relative risk, attributable risk, odds ratio, and likelihood ratio of malaria occurrence in exposed patients were determined by Chi-square (and Fisher's exact) test. The prevalence of asymptomatic malaria was 10.14% (63/621), with a higher prevalence among the pregnant women in the rural setting (12.21%; 37/303), than the urban setting (8.18%; 26/318). As indicated by the attributable risk, 21% of malaria incidence was attributed to absence of LLINs distribution in neighborhoods of the rural setting meanwhile 10% of malaria incidence is attributed to absence of LLINs distribution in neighborhoods of the urban setting. Regular screening for asymptomatic malaria in pregnancy and consistent free distribution of LLINs are recommended in endemic areas, especially in the rural settings.
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Mbakop LR, Awono-Ambene PH, Ekoko WE, Mandeng SE, Nwane P, Fesuh BN, Toto JC, Alenou LD, Onguina HG, Piameu M, Fomena A, Etang J. Malaria Transmission and Vector Resistance to Insecticides in a Changing Environment: Case of Simbock in Yaoundé-City, Cameroon. FRONTIERS IN TROPICAL DISEASES 2022. [DOI: 10.3389/fitd.2022.902211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Ecological upheavals resulting from uncontrolled urbanization can lead to significant changes in vector borne diseases’ profiles, thus requiring a thorough revision of their prevention and control strategies. The current study aimed at characterizing malaria vector populations in the Simbock neighborhood of Yaoundé-city (Cameroon), in relation to its urbanization scheme. Adult mosquitoes were captured by human landing catches (HLC) in- and outdoors prior to (2000–2006) and during infrastructural development (2014–2016). Anophelines were morphologically identified and analyzed for Plasmodium (P.) falciparum circumsporozoite protein detection using the ELISA technique. Species of the Anopheles (An.) gambiae complex were identified using SINE-PCR. Adult An. gambiae s.l. from larvae collected between 2014 and 2017 were tested for susceptibility to insecticides (0.1% bendiocarb, 4% DDT, 0.75% permethrin and 0.05% deltamethrin) with or without piperonyl butoxide (PBO) synergist, using WHO standard bioassays. The Hot Oligonucleotide Ligation Assay was used to detect the knockdown resistance (kdr) L995F/S mutations. Overall, nine malaria vector species were identified in 2000-2006, mostly An. moucheti (49%), An. nili (13.5%) and An. gambiae s.l. (12%); the six remaining species were represented at less than 3% each. However, only three species were found in 2014-2016, with increasing proportions of An. gambiae s.l. (67%) and An. funestus (32%) (P<0.0001). An. gambiae s.l. consisted An. coluzzii (> 85%) and An. gambiae (<15%) species during the two study periods. Plasmodium falciparum infection rates were 2.1% and 1.0% in 2000-2006 and 2014-2016 respectively (P=0.4), with decreasing entomological inoculation rates (EIR) from 0.34 infective bites per man per night (ib/m/n) to 0.02 ib/m/n (P<0.0001). Anopheles gambiae s.l. was resistant to DDT and permethrin [<40% mortality rates (MR)], and deltamethrin (65-89% MR), but fully susceptible to bendiocarb (100% MR). Pre-exposure of mosquitoes to PBO resulted in 90-100% MR to deltamethrin but not to permethrin. Furthermore, the two kdr L995F/S resistance alleles were recorded at 0.64 and 0.006 frequencies respectively. This study highlights a shift from rural to urban malaria transmission in Simbock, coupled with DDT and pyrethroid resistance in An. gambiae s.l. Combination vector control interventions, e.g., PBO nets and bendiocarb indoor residual spraying are needed in such areas.
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9
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Jones CM, Ciubotariu II, Muleba M, Lupiya J, Mbewe D, Simubali L, Mudenda T, Gebhardt ME, Carpi G, Malcolm AN, Kosinski KJ, Romero-Weaver AL, Stevenson JC, Lee Y, Norris DE. Multiple Novel Clades of Anopheline Mosquitoes Caught Outdoors in Northern Zambia. FRONTIERS IN TROPICAL DISEASES 2021; 2. [PMID: 35983564 PMCID: PMC9384971 DOI: 10.3389/fitd.2021.780664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Residual vector populations that do not come in contact with the most frequently utilized indoor-directed interventions present major challenges to global malaria eradication. Many of these residual populations are mosquito species about which little is known. As part of a study to assess the threat of outdoor exposure to malaria mosquitoes within the Southern and Central Africa International Centers of Excellence for Malaria Research, foraging female anophelines were collected outside households in Nchelenge District, northern Zambia. These anophelines proved to be more diverse than had previously been reported in the area. In order to further characterize the anopheline species, sequencing and phylogenetic approaches were utilized. Anopheline mosquitoes were collected from outdoor light traps, morphologically identified, and sent to Johns Hopkins Bloomberg School of Public Health for sequencing. Sanger sequencing from 115 field-derived samples yielded mitochondrial COI sequences, which were aligned with a homologous 488 bp gene segment from known anophelines (n = 140) retrieved from NCBI. Nuclear ITS2 sequences (n = 57) for at least one individual from each unique COI clade were generated and compared against NCBI’s nucleotide BLAST database to provide additional evidence for taxonomical identity and structure. Molecular and morphological data were combined for assignment of species or higher taxonomy. Twelve phylogenetic groups were characterized from the COI and ITS2 sequence data, including the primary vector species Anopheles funestus s.s. and An. gambiae s.s. An unexpectedly large proportion of the field collections were identified as An. coustani and An. sp. 6. Six phylogenetic groups remain unidentified to species-level. Outdoor collections of anopheline mosquitoes in areas frequented by people in Nchelenge, northern Zambia, proved to be extremely diverse. Morphological misidentification and underrepresentation of some anopheline species in sequence databases confound efforts to confirm identity of potential malaria vector species. The large number of unidentified anophelines could compromise the malaria vector surveillance and malaria control efforts not only in northern Zambia but other places where surveillance and control are focused on indoor-foraging and resting anophelines. Therefore, it is critical to continue development of methodologies that allow better identification of these populations and revisiting and cleaning current genomic databases.
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Affiliation(s)
- Christine M. Jones
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
| | - Ilinca I. Ciubotariu
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States
| | | | - James Lupiya
- Tropical Diseases Research Centre, Ndola, Zambia
| | - David Mbewe
- Tropical Diseases Research Centre, Ndola, Zambia
| | | | | | - Mary E. Gebhardt
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
| | - Giovanna Carpi
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States
| | - Ashley N. Malcolm
- Florida Medical Entomology Laboratory, Department of Entomology and Nematology, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL, United States
| | - Kyle J. Kosinski
- Florida Medical Entomology Laboratory, Department of Entomology and Nematology, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL, United States
| | - Ana L. Romero-Weaver
- Florida Medical Entomology Laboratory, Department of Entomology and Nematology, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL, United States
| | - Jennifer C. Stevenson
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
| | - Yoosook Lee
- Florida Medical Entomology Laboratory, Department of Entomology and Nematology, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL, United States
- Correspondence: Yoosook Lee, ; Douglas E. Norris,
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10
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Bamou R, Mayi MPA, Djiappi-Tchamen B, Nana-Ndjangwo SM, Nchoutpouen E, Cornel AJ, Awono-Ambene P, Parola P, Tchuinkam T, Antonio-Nkondjio C. An update on the mosquito fauna and mosquito-borne diseases distribution in Cameroon. Parasit Vectors 2021; 14:527. [PMID: 34635176 PMCID: PMC8507310 DOI: 10.1186/s13071-021-04950-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 08/12/2021] [Indexed: 11/10/2022] Open
Abstract
The expansion of mosquito-borne diseases such as dengue, yellow fever, and chikungunya in the past 15 years has ignited the need for active surveillance of common and neglected mosquito-borne infectious diseases. The surveillance should be designed to detect diseases and to provide relevant field-based data for developing and implementing effective control measures to prevent outbreaks before significant public health consequences can occur. Mosquitoes are important vectors of human and animal pathogens, and knowledge on their biodiversity and distribution in the Afrotropical region is needed for the development of evidence-based vector control strategies. Following a comprehensive literature search, an inventory of the diversity and distribution of mosquitoes as well as the different mosquito-borne diseases found in Cameroon was made. A total of 290 publications/reports and the mosquito catalogue website were consulted for the review. To date, about 307 species, four subspecies and one putative new species of Culicidae, comprising 60 species and one putative new species of Anopheles, 67 species and two subspecies of Culex, 77 species and one subspecies of Aedes, 31 species and one subspecies of Eretmapodites, two Mansonia, eight Coquillettidia, and 62 species with unknown medical and veterinary importance (Toxorhynchites, Uranotaenia, Mimomyia, Malaya, Hodgesia, Ficalbia, Orthopodomyia, Aedeomyia, and Culiseta and Lutzia) have been collected in Cameroon. Multiple mosquito species implicated in the transmission of pathogens within Anopheles, Culex, Aedes, Eretmapodites, Mansonia, and Coquillettidia have been reported in Cameroon. Furthermore, the presence of 26 human and zoonotic arboviral diseases, one helminthic disease, and two protozoal diseases has been reported. Information on the bionomics, taxonomy, and distribution of mosquito species will be useful for the development of integrated vector management programmes for the surveillance and elimination of mosquito-borne diseases in Cameroon. ![]()
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Affiliation(s)
- Roland Bamou
- Vector Borne Diseases Laboratory of the Biology and Applied Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang, Cameroon. .,Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon. .,Aix Marseille Univ, IRD, SSA, AP-HM, UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Marseille, France. .,IHU Méditerranée Infection, Marseille, France.
| | - Marie Paul Audrey Mayi
- Vector Borne Diseases Laboratory of the Biology and Applied Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang, Cameroon
| | - Borel Djiappi-Tchamen
- Vector Borne Diseases Laboratory of the Biology and Applied Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang, Cameroon.,Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon
| | - Stella Mariette Nana-Ndjangwo
- Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon.,Laboratoire de Parasitologie et d'écologie, Université de Yaoundé 1, Yaoundé, Cameroun
| | - Elysée Nchoutpouen
- Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon
| | - Antony John Cornel
- Department of Entomology and Nematology, Mosquito Control Research Laboratory, University of California, Davis, California, USA
| | - Parfait Awono-Ambene
- Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon
| | - Phillipe Parola
- Aix Marseille Univ, IRD, SSA, AP-HM, UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Marseille, France.,IHU Méditerranée Infection, Marseille, France
| | - Timoléon Tchuinkam
- Vector Borne Diseases Laboratory of the Biology and Applied Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, Dschang, Cameroon
| | - Christophe Antonio-Nkondjio
- Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroon.,Vector Biology Liverpool School of Tropical Medicine, Liverpool, UK
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11
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Efficacy of broflanilide (VECTRON T500), a new meta-diamide insecticide, for indoor residual spraying against pyrethroid-resistant malaria vectors. Sci Rep 2021; 11:7976. [PMID: 33846394 PMCID: PMC8042056 DOI: 10.1038/s41598-021-86935-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 03/18/2021] [Indexed: 11/09/2022] Open
Abstract
The rotational use of insecticides with different modes of action for indoor residual spraying (IRS) is recommended for improving malaria vector control and managing insecticide resistance. Insecticides with new chemistries are urgently needed. Broflanilide is a newly discovered insecticide under consideration. We investigated the efficacy of a wettable powder (WP) formulation of broflanilide (VECTRON T500) for IRS on mud and cement wall substrates in laboratory and experimental hut studies against pyrethroid-resistant malaria vectors in Benin, in comparison with pirimiphos-methyl CS (Actellic 300CS). There was no evidence of cross-resistance to pyrethroids and broflanilide in CDC bottle bioassays. In laboratory cone bioassays, broflanilide WP-treated substrates killed > 80% of susceptible and pyrethroid-resistant An. gambiae sl for 6–14 months. At application rates of 100 mg/m2 and 150 mg/m2, mortality of wild pyrethroid-resistant An. gambiae sl entering experimental huts in Covè, Benin treated with VECTRON T500 was similar to pirimiphos-methyl CS (57–66% vs. 56%, P > 0.05). Throughout the 6-month hut trial, monthly wall cone bioassay mortality on VECTRON T500 treated hut walls remained > 80%. IRS with broflanilide shows potential to significantly improve the control of malaria transmitted by pyrethroid-resistant mosquito vectors and could thus be a crucial addition to the current portfolio of IRS insecticides.
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12
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Cross DE, Thomas C, McKeown N, Siaziyu V, Healey A, Willis T, Singini D, Liywalii F, Silumesii A, Sakala J, Smith M, Macklin M, Hardy AJ, Shaw PW. Geographically extensive larval surveys reveal an unexpected scarcity of primary vector mosquitoes in a region of persistent malaria transmission in western Zambia. Parasit Vectors 2021; 14:91. [PMID: 33522944 PMCID: PMC7849156 DOI: 10.1186/s13071-020-04540-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 12/11/2020] [Indexed: 11/10/2022] Open
Abstract
Background The Barotse floodplains of the upper Zambezi River and its tributaries are a highly dynamic environment, with seasonal flooding and transhumance presenting a shifting mosaic of potential larval habitat and human and livestock blood meals for malaria vector mosquitoes. However, limited entomological surveillance has been undertaken to characterize the vector community in these floodplains and their environs. Such information is necessary as, despite substantial deployment of insecticide-treated nets (ITNs) and indoor residual spraying (IRS) against Anopheles vectors, malaria transmission persists across Barotseland in Zambia’s Western Province. Methods Geographically extensive larval surveys were undertaken in two health districts along 102 km of transects, at fine spatial resolution, during a dry season and following the peak of the successive wet season. Larvae were sampled within typical Anopheles flight range of human settlements and identified through genetic sequencing of cytochrome c oxidase I and internal transcribed spacer two regions of mitochondrial and nuclear DNA. This facilitated detailed comparison of taxon-specific abundance patterns between ecological zones differentiated by hydrological controls. Results An unexpected paucity of primary vectors was revealed, with An. gambiae s.l. and An. funestus representing < 2% of 995 sequenced anophelines. Potential secondary vectors predominated in the vector community, primarily An. coustani group species and An. squamosus. While the distribution of An. gambiae s.l. in the study area was highly clustered, secondary vector species were ubiquitous across the landscape in both dry and wet seasons, with some taxon-specific relationships between abundance and ecological zones by season. Conclusions The diversity of candidate vector species and their high relative abundance observed across diverse hydro-ecosystems indicate a highly adaptable transmission system, resilient to environmental variation and, potentially, interventions that target only part of the vector community. Larval survey results imply that residual transmission of malaria in Barotseland is being mediated predominantly by secondary vector species, whose known tendencies for crepuscular and outdoor biting renders them largely insensitive to prevalent vector control methods.![]()
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Affiliation(s)
- Dónall Eoin Cross
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, SY23 3FG, UK
| | - Chris Thomas
- Lincoln Centre for Water and Planetary Health, School of Geography, College of Science, Think Tank, University of Lincoln, Ruston Way, Lincoln, LN6 7DW, UK.
| | - Niall McKeown
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, SY23 3FG, UK
| | - Vincent Siaziyu
- Limulunga District Health Office, P.O. Box 910022, Mongu, Zambia
| | - Amy Healey
- Lincoln Centre for Water and Planetary Health, School of Geography, College of Science, Think Tank, University of Lincoln, Ruston Way, Lincoln, LN6 7DW, UK
| | - Tom Willis
- School of Geography, University of Leeds, Leeds, LS2 9JT, UK
| | - Douglas Singini
- Provincial Health Office, Western Province, P.O. Box 910022, Mongu, Zambia.,School of Public Health and Health Systems, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Francis Liywalii
- Provincial Health Office, Western Province, P.O. Box 910022, Mongu, Zambia
| | | | - Jacob Sakala
- Provincial Health Office, Western Province, P.O. Box 910022, Mongu, Zambia
| | - Mark Smith
- School of Geography, University of Leeds, Leeds, LS2 9JT, UK
| | - Mark Macklin
- Lincoln Centre for Water and Planetary Health, School of Geography, College of Science, Think Tank, University of Lincoln, Ruston Way, Lincoln, LN6 7DW, UK
| | - Andy J Hardy
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK
| | - Paul W Shaw
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, SY23 3FG, UK.,Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, South Africa
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13
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Murindahabi MM, Takken W, Misago X, Niyituma E, Umupfasoni J, Hakizimana E, van Vliet AJH, Poortvliet PM, Mutesa L, Murindahabi NK, Koenraadt CJM. Monitoring mosquito nuisance for the development of a citizen science approach for malaria vector surveillance in Rwanda. Malar J 2021; 20:36. [PMID: 33423679 PMCID: PMC7798336 DOI: 10.1186/s12936-020-03579-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 12/31/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Many countries, including Rwanda, have mosquito monitoring programmes in place to support decision making in the fight against malaria. However, these programmes can be costly, and require technical (entomological) expertise. Involving citizens in data collection can greatly support such activities, but this has not yet been thoroughly investigated in a rural African context. METHODS Prior to the implementation of such a citizen-science approach, a household entomological survey was conducted in October-November 2017 and repeated one year later in Busoro and Ruhuha sectors, in southern and eastern province of Rwanda, respectively. The goal was to evaluate the perception of mosquito nuisance reported by citizens as a potential indicator for malaria vector hotspots. Firstly, mosquito abundance and species composition were determined using Centers for Disease Control and Prevention (CDC) light traps inside the houses. Secondly, household members were interviewed about malaria risk factors and their perceived level of mosquito nuisance. RESULTS Tiled roofs, walls made of mud and wood, as well as the number of occupants in the house were predictors for the number of mosquitoes (Culicidae) in the houses, while the presence of eaves plus walls made of mud and wood were predictors for malaria vector abundance. Perception of mosquito nuisance reported indoors tended to be significantly correlated with the number of Anopheles gambiae sensu lato (s.l.) and Culicidae collected indoors, but this varied across years and sectors. At the village level, nuisance also significantly correlated with An. gambiae s.l. and total mosquito density, but only in 2018 while not in 2017. CONCLUSIONS Perception of mosquito nuisance denoted in a questionnaire survey could be used as a global indicator of malaria vector hotspots. Hence, involving citizens in such activities can complement malaria vector surveillance and control.
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Affiliation(s)
- Marilyn Milumbu Murindahabi
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,College of Sciences and Technology, University of Rwanda, Kigali, Rwanda
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Xavier Misago
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Elias Niyituma
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Jackie Umupfasoni
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Emmanuel Hakizimana
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Arnold J H van Vliet
- Environmental Systems Analysis Group, Wageningen University & Research, Wageningen, The Netherlands
| | - P Marijn Poortvliet
- Strategic Communication Group, Wageningen University & Research, Wageningen, the Netherlands
| | - Leon Mutesa
- College of Medicine and Health Sciences, University of Rwanda, Kigali, Rwanda
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14
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Influence of a Major Mountainous Landscape Barrier (Mount Cameroon) on the Spread of Metabolic ( GSTe2) and Target-Site ( Rdl) Resistance Alleles in the African Malaria Vector Anopheles funestus. Genes (Basel) 2020; 11:genes11121492. [PMID: 33322524 PMCID: PMC7764057 DOI: 10.3390/genes11121492] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/05/2020] [Accepted: 12/08/2020] [Indexed: 12/03/2022] Open
Abstract
Increased levels of insecticide resistance in major malaria vectors such as Anopheles funestus threaten the effectiveness of insecticide-based control programmes. Understanding the landscape features impacting the spread of resistance makers is necessary to design suitable resistance management strategies. Here, we examined the influence of the highest mountain in West Africa (Mount Cameroon; 4095 m elevation) on the spread of metabolic and target-site resistance alleles in An. funestus populations. Vector composition varied across the four localities surveyed along the altitudinal cline with major vectors exhibiting high parity rate (80.5%). Plasmodium infection rates ranged from 0.79% (An. melas) to 4.67% (An. funestus). High frequencies of GSTe2R (67–81%) and RdlR (49–90%) resistance alleles were observed in An. funestus throughout the study area, with GSTe2R frequency increasing with altitude, whereas the opposite is observed for RdlR. Patterns of genetic diversity and population structure analyses revealed high levels of polymorphisms with 12 and 16 haplotypes respectively for GSTe2 and Rdl. However, the reduced diversity patterns of resistance allele carriers revealed signatures of positive selection on the two genes across the study area irrespective of the altitude. Despite slight variations associated with the altitude, the spread of resistance alleles suggest that control strategies could be implemented against malaria vectors across mountainous landscapes.
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15
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Bango ZA, Tawe L, Muthoga CW, Paganotti GM. Past and current biological factors affecting malaria in the low transmission setting of Botswana: A review. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2020; 85:104458. [PMID: 32668367 PMCID: PMC7354381 DOI: 10.1016/j.meegid.2020.104458] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 11/29/2022]
Abstract
Malaria continues to be one of the top infectious agents contributing to morbidity and mortality in sub-Saharan Africa. Annually, Botswana accounts only for a small proportion of cases (<<1%). Despite significantly reduced incidence rate, the country still experiences sporadic outbreaks that hamper the goal of malaria elimination. This review evaluated previous and current biological factors that impact malaria in Botswana, specifically focussing on the vectors, the parasite and the host. This was accomplished via a literature review evaluating these variables in Botswana. Current literature suggests that Anopheles arabiensis is the main malaria vector in the country. Several other potential vectors have been found widely distributed throughout Botswana in high numbers, yet remain largely unstudied with regards to their contribution to the country's malaria burden. We also report the most up to date list of all Anopheles species that have been found in Botswana. Plasmodium falciparum is responsible for the vast majority of symptomatic malaria in the country and some drug resistance markers have been documented for this species. Plasmodium vivax has been reported in asymptomatic subjects, even though a large proportion of the Botswana population appears to be Duffy antigen negative. Very little is known about the true distribution of P. vivax and no point of care testing infrastructure for this species exists in Botswana, making it difficult to tailor treatment to address possible recrudescence or relapse. Due to a genetically diverse population with a substantial Khoisan contribution into the Bantu genetic background, several phenotypes that potentially impact prevalence and severity of malaria exist within the country. These include sickle cell trait, Glucose-6-Phosphate Dehydrogenase deficiency, and Duffy negativity. This review highlights the information that currently exists on malaria in Botswana. It also postulates that a comprehensive understanding of these aforementioned biological factors may help to explain malaria persistence in Botswana.
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Affiliation(s)
| | - Leabaneng Tawe
- Botswana-University of Pennsylvania Partnership, Gaborone, Botswana; Department of Medical Laboratory Sciences, Faculty of Health Sciences, University of Botswana, Gaborone, Botswana
| | | | - Giacomo Maria Paganotti
- Botswana-University of Pennsylvania Partnership, Gaborone, Botswana; Division of Infectious Diseases, Perelman School of Medicine, University of Pennsylvania, PA, USA; Department of Biomedical Sciences, University of Botswana, Gaborone, Botswana.
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16
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Assessment of Malaria Predisposing Factors among Crop Production Farmers Attending the Ndop District Hospital, Northwest Region of Cameroon. J Parasitol Res 2020; 2020:1980709. [PMID: 32802483 PMCID: PMC7416250 DOI: 10.1155/2020/1980709] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 06/02/2020] [Accepted: 07/24/2020] [Indexed: 01/08/2023] Open
Abstract
The widespread impacts of malaria in the tropical regions of the developing world are not only on healthcare issues but also an agricultural output. Malaria causes manpower loss when it strikes farmers at critical planting, weeding, and harvesting times. Given the above, the expected outcome to malaria prevention programs in farming communities remains a far cry, especially where the predisposing factors are not properly identified and long-lasting solutions proffered. Consequently, this study was designed to assess the malaria predisposing factors among the crop production farmers attending the Ndop District Hospital. The microscopy method was used to determine the presence of malaria parasitaemia. The following categorical variables were considered predisposing factors: Sex, history on malaria illness/treatment, use of long-lasting insecticide nets (LLINs) and knowledge on malaria transmission/prevention. A four-point Likert-type rating scale was adopted for the scoring of the responses given on the predisposing factors, while Fisher's exact test was used to assess the associations between malaria and each of the predisposing factors. The prevalence of malaria parasitaemia among the crop production farmers was 20% (143/715). The predisposing factors tested were found to be significantly associated to the occurrence of malaria among the crop production farmers. Therefore, the combination of improved existing and innovative malaria control strategies may possibly ensure sustained malaria decrease among the farmers in the Ndop Health District.
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17
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Effect of Impregnated Mosquito Bed Nets on the Prevalence of Malaria among Pregnant Women in Foumban Subdivision, West Region of Cameroon. J Parasitol Res 2020; 2020:7438317. [PMID: 32733698 PMCID: PMC7383309 DOI: 10.1155/2020/7438317] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 05/02/2020] [Accepted: 05/09/2020] [Indexed: 11/18/2022] Open
Abstract
Background Malaria is one of the major public health problems in many tropical developing countries including Cameroon. Impregnated mosquito bed nets are one of the control measures put in place by the WHO and adopted by the Cameroon's Ministry of Public Health to fight against malaria in pregnancy. This study was a population-based cross-sectional study that investigated the level of adherence, respondent's knowledge, altitude, and practices toward malaria prevention and control. Methods To investigate this, a sample size of 410 pregnant women who were inhabitants of Foumban Subdivision was examined. Data on net ownership versus usage, pregnancy status, and socioeconomic background were collected using a questionnaire. Parasitological tests for malaria parasites were carried out using peripheral blood samples obtained from finger pricks of the pregnant women for the preparation of thick blood smear and RDTs. Results Two hundred and eighteen tested positive (53.4%) with the highest prevalence occurring during the first trimester (79.6%) and in primigravidae (68.8%). Participants believed that mosquito bed nets can protect them against malaria infection. The highest number (81.0%) of the women who had mosquito nets acquired them during antenatal visits. Among those who possessed nets, 42.7% adhered to sleeping under them and few (50%) experienced problems of sweating, discomfort, and heat. Also, the study revealed a high prevalence rate of 63.8% for those who did not use nets during pregnancy as compared to those who owned and used them. Conclusion The findings indicated that increased access to impregnated mosquito bed nets is required to lower the risk of malaria infection amongst pregnant women. The Cameroon government should improve health education to families within the locality and pursue an integrated approach to fight against mosquitoes during the rainy season.
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Antonio-Nkondjio C, Ndo C, Njiokou F, Bigoga JD, Awono-Ambene P, Etang J, Ekobo AS, Wondji CS. Review of malaria situation in Cameroon: technical viewpoint on challenges and prospects for disease elimination. Parasit Vectors 2019; 12:501. [PMID: 31655608 PMCID: PMC6815446 DOI: 10.1186/s13071-019-3753-8] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 10/18/2019] [Indexed: 11/30/2022] Open
Abstract
Malaria still has a devastating impact on public health and welfare in Cameroon. Despite the increasing number of studies conducted on disease prevalence, transmission patterns or treatment, there are to date, not enough studies summarising findings from previous works in order to identify gaps in knowledge and areas of interest where further evidence is needed to drive malaria elimination efforts. The present study seeks to address these gaps by providing a review of studies conducted so far on malaria in Cameroon since the 1940s to date. Over 250 scientific publications were consulted for this purpose. Although there has been increased scale-up of vector control interventions which significantly reduced the morbidity and mortality to malaria across the country from a prevalence of 41% of the population reporting at least one malaria case episode in 2000 to a prevalence of 24% in 2017, the situation is not yet under control. There is a high variability in disease endemicity between epidemiological settings with prevalence of Plasmodium parasitaemia varying from 7 to 85% in children aged 6 months to 15 years after long-lasting insecticidal nets (LLINs) scale-up. Four species of Plasmodium have been recorded across the country: Plasmodium falciparum, P. malariae, P. ovale and P. vivax. Several primate-infecting Plasmodium spp. are also circulating in Cameroon. A decline of artemisinin-based combinations therapeutic efficacy from 97% in 2006 to 90% in 2016 have been reported. Several mutations in the P. falciparum chloroquine resistance (Pfcrt) and P. falciparum multidrug resistance 1 (Pfmdr1) genes conferring resistance to either 4-amino-quinoleine, mefloquine, halofanthrine and quinine have been documented. Mutations in the Pfdhfr and Pfdhps genes involved in sulfadoxine-pyrimethamine are also on the rise. No mutation associated with artemisinin resistance has been recorded. Sixteen anopheline species contribute to malaria parasite transmission with six recognized as major vectors: An. gambiae, An. coluzzii, An. arabiensis, An. funestus, An. nili and An. moucheti. Studies conducted so far, indicated rapid expansion of DDT, pyrethroid and carbamate resistance in An. gambiae, An. coluzzii, An. arabiensis and An. funestus threatening the performance of LLINs. This review highlights the complex situation of malaria in Cameroon and the need to urgently implement and reinforce integrated control strategies in different epidemiological settings, as part of the substantial efforts to consolidate gains and advance towards malaria elimination in the country.
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Affiliation(s)
- Christophe Antonio-Nkondjio
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B. P.288 Yaoundé, Cameroun
- Centre for Research in Infectious Disease (CRID), P.O. Box 13591, Yaoundé, Cameroon
- Vector Biology Liverpool School of Tropical medicine Pembroke Place, Liverpool, UK
| | - Cyrille Ndo
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 24157, Douala, Cameroon
- Centre for Research in Infectious Disease (CRID), P.O. Box 13591, Yaoundé, Cameroon
| | - Flobert Njiokou
- Centre for Research in Infectious Disease (CRID), P.O. Box 13591, Yaoundé, Cameroon
- Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Jude D. Bigoga
- Laboratory for Vector Biology and control, National Reference Unit for Vector Control, The Biotechnology Center, Nkolbisson-University of Yaounde I, P.O. Box 3851, Messa, Yaounde, Cameroon
- Department of Biochemistry, Faculty of Science, University of Yaounde I, Yaounde, Cameroon
| | - Parfait Awono-Ambene
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B. P.288 Yaoundé, Cameroun
| | - Josiane Etang
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B. P.288 Yaoundé, Cameroun
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 24157, Douala, Cameroon
- Institute for Insect Biotechnology, Justus Liebig University Gießen, Winchester Str. 2, 35394 Gießen, Germany
| | - Albert Same Ekobo
- Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Charles S. Wondji
- Centre for Research in Infectious Disease (CRID), P.O. Box 13591, Yaoundé, Cameroon
- Vector Biology Liverpool School of Tropical medicine Pembroke Place, Liverpool, UK
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Mbakop LR, Awono-Ambene PH, Mandeng SE, Ekoko WE, Fesuh BN, Antonio-Nkondjio C, Toto JC, Nwane P, Fomena A, Etang J. Malaria Transmission around the Memve'ele Hydroelectric Dam in South Cameroon: A Combined Retrospective and Prospective Study, 2000⁻2016. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 16:ijerph16091618. [PMID: 31075820 PMCID: PMC6539953 DOI: 10.3390/ijerph16091618] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 03/08/2019] [Accepted: 03/12/2019] [Indexed: 11/16/2022]
Abstract
Dam constructions are considered a great concern for public health. The current study aimed to investigate malaria transmission in the Nyabessan village around the Memve'ele dam in South Cameroon. Adult mosquitoes were captured by human landing catches in Nyabessan before and during dam construction in 2000-2006 and 2014-2016 respectively, as well as in the Olama village, which was selected as a control. Malaria vectors were morphologically identified and analyzed for Plasmodium falciparum circumsporozoite protein detection and molecular identification of Anopheles (A.) gambiae species. Overall, ten malaria vector species were identified among 12,189 Anopheles specimens from Nyabessan (N = 6127) and Olama (N = 6062), including A. gambiae Giles (1902), A. coluzzii Coetzee (2013), A. moucheti Evans (1925), A. ovengensis Awono (2004), A. nili Theobald (1903), A. paludis Theobald (1900), A. zieanni, A. marshallii Theobald (1903), A. coustani Laveran (1900), and A. obscurus Grünberg (1905). In Nyabessan, A. moucheti and A. ovengensis were the main vector species before dam construction (16-50 bites/person/night-b/p/n, 0.26-0.71 infective bites/person/night-ib/p/n) that experienced a reduction of their role in disease transmission in 2016 (3-35 b/p/n, 0-0.5 ib/p/n) (p < 0.005). By contrast, the role of A. gambiae s.l. and A. paludis increased (11-38 b/p/n, 0.75-1.2 ib/p/n) (p < 0.01). In Olama, A. moucheti remained the main malaria vector species throughout the study period (p = 0.5). These findings highlight the need for a strong vector-borne disease surveillance and control system around the Memve'ele dam.
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Affiliation(s)
- Lili R Mbakop
- Laboratory of Animal Biology and Physiology, Faculty of Sciences, University of Yaoundé I, P.O. Box 337 Yaoundé, Cameroon.
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
| | - Parfait H Awono-Ambene
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
| | - Stanislas E Mandeng
- Laboratory of Animal Biology and Physiology, Faculty of Sciences, University of Yaoundé I, P.O. Box 337 Yaoundé, Cameroon.
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
| | - Wolfgang E Ekoko
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
- Laboratory of Animal Biology and Physiology, University of Douala, P.O. Box 24157 Douala, Cameroon.
| | - Betrand N Fesuh
- Laboratoire d'Ingénierie Mathématique et Systèmes d'Information, Ecole Nationale Supérieure de Polytechnique (ENSP), Université de Yaoundé I, B.P. 337 Yaoundé, Cameroun.
| | - Christophe Antonio-Nkondjio
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
| | - Jean-Claude Toto
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
| | - Philippe Nwane
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
- Centre de Recherche sur les Filarioses et Maladies Tropicales (CRFilMT), B.P. 5797 Yaoundé, Cameroun.
| | - Abraham Fomena
- Laboratory of Animal Biology and Physiology, Faculty of Sciences, University of Yaoundé I, P.O. Box 337 Yaoundé, Cameroon.
| | - Josiane Etang
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroun.
- Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 2701 Douala, Cameroon.
- Institute for Insect Biotechnology, Justus-Liebig University Gießen, Winchesterstr. 2, 35394 Gießen, Germany.
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Amvongo-Adjia N, Wirsiy EL, Riveron JM, Chounna Ndongmo WP, Enyong PA, Njiokou F, Wondji CS, Wanji S. Bionomics and vectorial role of anophelines in wetlands along the volcanic chain of Cameroon. Parasit Vectors 2018; 11:471. [PMID: 30107815 PMCID: PMC6092805 DOI: 10.1186/s13071-018-3041-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Accepted: 07/30/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The epidemiological profiles of vector-borne diseases, such as malaria, are strongly associated with landscape components. The reduction of malaria burden in endemic and epidemic regions mainly depends on knowledge of the malaria-transmitting mosquito species, populations and behavioural characteristics, as well as malaria exposure risks. This work aimed at carrying out a holistic study in order to characterise Anopheles species in relation to human malaria in seven wetlands along the lower section of the volcanic chain of Cameroon. RESULTS Eight malaria vectors: Anopheles arabiensis, An. coluzzii, An. funestus (s.s.), An. gambiae, An. hancocki, An. melas, An. nili and An. ziemanni, were found biting humans. Anopheles gambiae was widespread; however, it played a secondary role in the Ndop plain where An. ziemmani was the primary vector species (79.2%). Anophelines were more exophagic (73.6%) than endophagic (26.4%), showing a marked nocturnal activity (22:00-4:00 h) for An. coluzzii and An. gambiae while An. funestus (s.s.) was mostly caught between 1:00 and 6:00 h and An. ziemanni having an early evening biting behaviour (18:00-00:00 h). Female Anopheles were mostly observed to have relative high parity rates (≥ 70%), with the exception of the Meanja site where species parity varies from 46 to 55%. Overall, the transmission level was low with entomological inoculation rates estimated to 0.7 infected bites per person per month (ib/p/mth) in Tiko and Ndop, 1.4 ib/p/mth in Mamfe and 2.24 ib/p/mth in Santchou. CONCLUSIONS The present study represents detailed Anopheles vector characterisation from an understudied area along the volcanic chain of Cameroon with endemic malaria transmission. The significant differences in bionomics and Anopheles species distribution within the studied wetlands, highlights the importance of providing baseline data and an opportunity to assess the outcome of ongoing malaria control interventions in the country.
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Affiliation(s)
- Nathalie Amvongo-Adjia
- Parasitology and Ecology Laboratory, Animal Biology and Physiology Department, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon. .,Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon. .,Centre for Medical Research, Institute of Medical Research and Medicinal Plants Studies (IMPM), Yaoundé, Cameroon.
| | - Emmanuela L Wirsiy
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasite and Vector Biology Research Unit (PAVBRU), Microbiology and Parasitology Department, University of Buea, Buea, Cameroon
| | - Jacob M Riveron
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Winston P Chounna Ndongmo
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasite and Vector Biology Research Unit (PAVBRU), Microbiology and Parasitology Department, University of Buea, Buea, Cameroon
| | - Peter A Enyong
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.,Parasite and Vector Biology Research Unit (PAVBRU), Microbiology and Parasitology Department, University of Buea, Buea, Cameroon
| | - Flobert Njiokou
- Parasitology and Ecology Laboratory, Animal Biology and Physiology Department, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon.,Centre for Research in Infectious Diseases (CRID), LSTM Research Unit, Yaoundé, Cameroon
| | - Charles S Wondji
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.,Centre for Research in Infectious Diseases (CRID), LSTM Research Unit, Yaoundé, Cameroon
| | - Samuel Wanji
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon. .,Parasite and Vector Biology Research Unit (PAVBRU), Microbiology and Parasitology Department, University of Buea, Buea, Cameroon.
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Hakizimana E, Karema C, Munyakanage D, Githure J, Mazarati JB, Tongren JE, Takken W, Binagwaho A, Koenraadt CJ. Spatio-temporal distribution of mosquitoes and risk of malaria infection in Rwanda. Acta Trop 2018; 182:149-157. [PMID: 29476726 DOI: 10.1016/j.actatropica.2018.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/26/2018] [Accepted: 02/11/2018] [Indexed: 11/24/2022]
Abstract
To date, the Republic of Rwanda has not systematically reported on distribution, diversity and malaria infectivity rate of mosquito species throughout the country. Therefore, we assessed the spatial and temporal variation of mosquitoes in the domestic environment, as well as the nocturnal biting behavior and infection patterns of the main malaria vectors in Rwanda. For this purpose, mosquitoes were collected monthly from 2010 to 2013 by human landing catches (HLC) and pyrethrum spray collections (PSC) in seven sentinel sites. Mosquitoes were identified using morphological characteristics and PCR. Plasmodium falciparum sporozoite infection rates were determined using ELISA. A total of 340,684 mosquitoes was collected by HLC and 73.8% were morphologically identified as culicines and 26.2% as anophelines. Of the latter, 94.3% were Anopheles gambiae s.l., 0.4% Anopheles funestus and 5.3% other Anopheles species. Of An. gambiae s.l., An. arabiensis and An. gambiae s.s. represented 84.4% and 15.6%, respectively. Of all An. gambiae s.l. collected indoor and outdoor, the proportion collected indoors was 51.3% in 2010 and 44.9% in 2013. A total of 17,022 mosquitoes was collected by PSC of which 20.5% were An. gambiae s.l. and 79.5% were culicines. For the seven sentinel sites, the mean indoor density for An. gambiae s.l. varied from 0.0 to 1.0 mosquitoes/house/night. P. falciparum infection rates in mosquitoes varied from 0.87 to 4.06%. The entomological inoculation rate (EIR) ranged from 1.0 to 329.8 with an annual average of 99.5 infective bites/person/year. This longitudinal study shows, for the first time, the abundance, species composition, and entomological inoculation rate of malaria mosquitoes collected throughout Rwanda.
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Awono-Ambene PH, Etang J, Antonio-Nkondjio C, Ndo C, Eyisap WE, Piameu MC, Mandeng ES, Mbakop RL, Toto JC, Patchoke S, Mnzava AP, Knox TB, Donnelly M, Fondjo E, D. Bigoga J. The bionomics of the malaria vector Anopheles rufipes Gough, 1910 and its susceptibility to deltamethrin insecticide in North Cameroon. Parasit Vectors 2018; 11:253. [PMID: 29669580 PMCID: PMC5907476 DOI: 10.1186/s13071-018-2809-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 03/25/2018] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Following the recent discovery of the role of Anopheles rufipes Gough, 1910 in human malaria transmission in the northern savannah of Cameroon, we report here additional information on its feeding and resting habits and its susceptibility to the pyrethroid insecticide deltamethrin. METHODS From 2011 to 2015, mosquito samples were collected in 38 locations across Garoua, Mayo Oulo and Pitoa health districts in North Cameroon. Adult anophelines collected using outdoor clay pots, window exit traps and indoor spray catches were checked for feeding status, blood meal origin and Plasmodium circumsporozoite protein. The susceptibility of field-collected An. rufipes to deltamethrin was assessed using WHO standard procedures. RESULTS Of 9327 adult Anopheles collected in the 38 study sites, An. rufipes (6.5%) was overall the fifth most abundant malaria vector species following An. arabiensis (52.4%), An. funestus (s.l.) (20.8%), An. coluzzii (12.6%) and An. gambiae (6.8%). This species was found outdoors (51.2%) or entering houses (48.8%) in 35 suburban and rural locations, together with main vector species. Apart from human blood with index of 37%, An. rufipes also fed on animals including cows (52%), sheep (49%), pigs (16%), chickens (2%) and horses (1%). The overall parasite infection rate of this species was 0.4% based on the detection of P. falciparum circumsporozoite proteins in two of 517 specimens tested. Among the 21 An. rufipes populations assessed for deltamethrin susceptibility, seven populations were classified as "susceptible" (mortality ≥ 98%) , ten as "probable resistant" with a mortality range of 90-97% and four as "resistant" with a mortality range of 80-89%. CONCLUSIONS This study revealed changeable resting and feeding behaviour of An. rufipes, as well as further evidence on its ability to carry human malaria parasites in North Cameroon. Besides, this species is developing physiological resistance to deltamethrin insecticide which is used in treated nets and agriculture throughout the country, and should be regarded as one of potential targets for the control of residual malaria parasite transmission in Africa.
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Affiliation(s)
- Parfait H. Awono-Ambene
- Research Institute of Yaounde (IRY), Organization de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon
| | - Josiane Etang
- Research Institute of Yaounde (IRY), Organization de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 2701, Douala, Cameroon
| | - Christophe Antonio-Nkondjio
- Research Institute of Yaounde (IRY), Organization de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon
| | - Cyrille Ndo
- Research Institute of Yaounde (IRY), Organization de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 2701, Douala, Cameroon
| | | | - Michael C. Piameu
- Ecole des Sciences de la Santé, Université Catholique d’Afrique Centrale, B.P. 1110, Yaoundé, Cameroon
| | - Elysée S. Mandeng
- Faculty of Sciences, University of Yaoundé I, P.O. Box 812, Yaounde, Cameroon
| | - Ranaise L. Mbakop
- Faculty of Sciences, University of Yaoundé I, P.O. Box 812, Yaounde, Cameroon
| | - Jean Claude Toto
- Research Institute of Yaounde (IRY), Organization de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon
| | - Salomon Patchoke
- National Malaria Control Programme, Ministry of Public Health, P.O. Box 14386, Yaoundé, Cameroon
| | - Abraham P. Mnzava
- The African Leaders Malaria Alliance (ALMA), 3 Barack Obama Drive, P.O. Box 70198, 11101 Dar es Salaam, Tanzania
| | - Tessa B. Knox
- Global Malaria Programme, World Health Organization, Avenue Appia, Geneva, Switzerland
| | - Martin Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA UK
| | - Etienne Fondjo
- National Malaria Control Programme, Ministry of Public Health, P.O. Box 14386, Yaoundé, Cameroon
| | - Jude D. Bigoga
- National Reference Unit for Vector Control, The Biotechnology Center, University of Yaoundé I, P.O. Box 3851-Messa, Yaoundé, Cameroon
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Tabue RN, Awono-Ambene P, Etang J, Atangana J, C AN, Toto JC, Patchoke S, Leke RGF, Fondjo E, Mnzava AP, Knox TB, Tougordi A, Donnelly MJ, Bigoga JD. Role of Anopheles (Cellia) rufipes (Gough, 1910) and other local anophelines in human malaria transmission in the northern savannah of Cameroon: a cross-sectional survey. Parasit Vectors 2017; 10:22. [PMID: 28077167 PMCID: PMC5225577 DOI: 10.1186/s13071-016-1933-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 12/08/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND As part of a study to determine the impact of insecticide resistance on the effectiveness of long-lasting insecticide treated nets (LLINs) in the north of Cameroon, the unexpectedly high density and anthropophilic behaviour of Anopheles rufipes lead us to investigate this species bionomics and role in human malaria parasite transmission. METHODS For four consecutive years (2011-2014), annual cross-sectional sampling of adult mosquitoes was conducted during the peak malaria season (September-October) in three health districts in northern Cameroon. Mosquitoes sampled by human landing catch and pyrethrum spray catch methods were morphologically identified, their ovaries dissected for parity determination and Anopheles gambiae siblings were identified by molecular assay. Infection with P. falciparum and blood meal source in residual fauna of indoor resting anopheline mosquitoes were determined by enzyme-linked-immunosorbent assays. RESULTS Anopheles gambiae (sensu lato) (s.l.) comprised 18.4% of mosquitoes collected with An. arabiensis representing 66.27% of the sibling species. The proportion of An. rufipes (2.7%) collected was high with a human-biting rate ranging between 0.441 and 11.083 bites/person/night (b/p/n) and an anthropophagic rate of 15.36%. Although overall the members of An. gambiae complex were responsible for most of the transmission with entomological inoculation rates (EIR) reaching 1.221 infective bites/person/night (ib/p/n), An. arabiensis and An. coluzzii were the most implicated. The roles of An. funestus, An. pharoensis and An. paludis were minor. Plasmodium falciparum circumsporozoite protein rate in Anopheles rufipes varied from 0.6 to 5.7% with EIR values between 0.010 and 0.481 ib/p/n. CONCLUSIONS The study highlights the epidemiological role of An. rufipes alongside the members of the An. gambiae complex, and several other sympatric species in human malaria transmission during the wet season in northern Cameroon. For the first time in Cameroon, An. rufipes has been shown to be an important local malaria vector, emphasising the need to review the malaria entomological profile across the country as pre-requisite to effective vector management strategies.
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Affiliation(s)
- Raymond N Tabue
- Faculty of Science, Department of Biochemistry, University of Yaounde I, P.O. Box 813- Messa, Yaounde, Cameroon.,National Reference Unit for Vector Control, The Biotechnology Center, University of Yaoundé I, P.O. Box 3851-Messa, Yaoundé, Cameroon.,Ministry of Public Health, National Malaria Control Programme, P.O. Box 14386, Yaoundé, Cameroon
| | - Parfait Awono-Ambene
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Josiane Etang
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Jean Atangana
- Ministry of Public Health, National Malaria Control Programme, P.O. Box 14386, Yaoundé, Cameroon
| | - Antonio-Nkondjio C
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Jean C Toto
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Salomon Patchoke
- Ministry of Public Health, National Malaria Control Programme, P.O. Box 14386, Yaoundé, Cameroon
| | - Rose G F Leke
- National Reference Unit for Vector Control, The Biotechnology Center, University of Yaoundé I, P.O. Box 3851-Messa, Yaoundé, Cameroon
| | - Etienne Fondjo
- Ministry of Public Health, National Malaria Control Programme, P.O. Box 14386, Yaoundé, Cameroon
| | - Abraham P Mnzava
- Global Malaria Programme, World Health Organization, Avenue Appia 20, Geneva, Switzerland
| | - Tessa B Knox
- Global Malaria Programme, World Health Organization, Avenue Appia 20, Geneva, Switzerland
| | - Alexis Tougordi
- WHO country Office in Cameroon, PO BOX 155, Yaounde, Cameroon
| | - Martin J Donnelly
- Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK.,Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Jude D Bigoga
- Faculty of Science, Department of Biochemistry, University of Yaounde I, P.O. Box 813- Messa, Yaounde, Cameroon. .,National Reference Unit for Vector Control, The Biotechnology Center, University of Yaoundé I, P.O. Box 3851-Messa, Yaoundé, Cameroon.
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Susceptibility of Anopheles gambiae to insecticides used for malaria vector control in Rwanda. Malar J 2016; 15:582. [PMID: 27905919 PMCID: PMC5134262 DOI: 10.1186/s12936-016-1618-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 11/15/2016] [Indexed: 11/10/2022] Open
Abstract
Background The widespread emergence of resistance to pyrethroids is a major threat to the gains made in malaria control. To monitor the presence and possible emergence of resistance against a variety of insecticides used for malaria control in Rwanda, nationwide insecticide resistance surveys were conducted in 2011 and 2013. Methods Larvae of Anopheles gambiae sensu lato mosquitoes were collected in 12 sentinel sites throughout Rwanda. These were reared to adults and analysed for knock-down and mortality using WHO insecticide test papers with standard diagnostic doses of the recommended insecticides. A sub-sample of tested specimens was analysed for the presence of knockdown resistance (kdr) mutations. Results A total of 14,311 mosquitoes were tested and from a sample of 1406 specimens, 1165 (82.9%) were identified as Anopheles arabiensis and 241 (17.1%) as Anopheles gambiae sensu stricto. Mortality results indicated a significant increase in resistance to lambda-cyhalothrin from 2011 to 2013 in 83% of the sites, permethrin in 25% of the sites, deltamethrin in 25% of the sites and DDT in 50% of the sites. Mosquitoes from 83% of the sites showed full susceptibility to bendiocarb and 17% of sites were suspected to harbour resistance that requires further confirmation. No resistance was observed to fenitrothion in all study sites during the entire survey. The kdr genotype results in An. gambiae s.s. showed that 67 (50%) possessed susceptibility (SS) alleles, while 35 (26.1%) and 32 (23.9%) mosquitoes had heterozygous (RS) and homozygous (RR) alleles, respectively. Of the 591 An. arabiensis genotyped, 425 (71.9%) possessed homozygous (SS) alleles while 158 (26.7%) and 8 (1.4%) had heterozygous (RS) and homozygous (RR) alleles, respectively. Metabolic resistance involving oxidase enzymes was also detected using the synergist PBO. Conclusion This is the first nationwide study of insecticide resistance in malaria vectors in Rwanda. It shows the gradual increase of insecticide resistance to pyrethroids (lambda-cyhalothrin, deltamethrin, permethrin) and organochlorines (DDT) and the large presence of target site insensitivity. The results demonstrate the need for Rwanda to expand monitoring for insecticide resistance including further metabolic resistance testing and implement an insecticide resistance management strategy to sustain the gains made in malaria control.
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Kenea O, Balkew M, Tekie H, Gebre-Michael T, Deressa W, Loha E, Lindtjørn B, Overgaard HJ. Human-biting activities of Anopheles species in south-central Ethiopia. Parasit Vectors 2016; 9:527. [PMID: 27716416 PMCID: PMC5045578 DOI: 10.1186/s13071-016-1813-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 09/22/2016] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are the key malaria vector control interventions in Ethiopia. The success of these interventions rely on their efficacy to repel or kill indoor feeding and resting mosquitoes. This study was undertaken to monitor human-biting patterns of Anopheles species in south-central Ethiopia. METHODS Human-biting patterns of anophelines were monitored for 40 nights in three houses using human landing catches (HLC) both indoors and outdoors between July and November 2014, in Edo Kontola village, south-central Ethiopia. This time coincides with the major malaria transmission season in Ethiopia, which is usually between September and November. Adult mosquitoes were collected from 19:00 to 06:00 h and identified to species. Comparisons of HLC data were done using incidence rate ratio (IRR) calculated by negative binomial regression. The nocturnal biting activities of each Anopheles species was expressed as mean number of mosquitoes landing per person per hour. To assess malaria infections in Anopheles mosquitoes the presence of Plasmodium falciparum and P. vivax circumsporozoite proteins (CSP) were determined by enzyme-linked immunosorbent assay (ELISA). RESULTS Altogether 3,408 adult female anophelines were collected, 2,610 (76.6 %) outdoors and 798 (23.4 %) indoors. Anopheles zeimanni was the predominant species (66.5 %) followed by An. arabiensis (24.8 %), An. pharoensis (6.8 %) and An. funestus (s.l.) (1.8 %). The overall mean anopheline density was 3.3 times higher outdoors than indoors (65.3 vs 19.9/person/night, IRR: 3.3, 95 % CI: 1.1-5.1, P = 0.001). The mean density of An. zeimanni, An. pharoensis and An. funestus (s.l.) collected outdoors was significantly higher than indoors for each species (P < 0.05). However, the mean An. arabiensis density outdoors was similar to that indoors (11.8 vs 9.4/person/night, IRR: 1.3, 95 % CI: 0.8-1.9, P = 0.335). The mean hourly human-biting density of An. arabiensis was greater outdoors than indoors and peaked between 21:00 and 22:00 h. However, An. arabiensis parous population showed high indoor man biting activities during bedtimes (22:00 to 05:00 h) when the local people were indoor and potentially protected by IRS and LLINs. All mosquito samples tested for CSP antigen were found negative to malaria parasites. CONCLUSIONS Results show much greater mosquito human-biting activities occurring outdoors than indoors and during early parts of the night, implying higher outdoor malaria transmission potential in the area. However, high bedtime (22:00 to 05:00 h) indoor biting activities of parous An. arabiensis suggest high potential intervention impact of IRS and LLINs on indoor malaria transmission.
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Affiliation(s)
- Oljira Kenea
- Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia
- Department of Biology, Wollega University, Nekemte, Ethiopia
| | - Meshesha Balkew
- Akililu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Habte Tekie
- Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Teshome Gebre-Michael
- Akililu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Wakgari Deressa
- Department of Preventive Medicine, School of Public Health, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Eskindir Loha
- School of Public and Environmental Health, Hawassa University, Hawassa, Ethiopia
| | - Bernt Lindtjørn
- Centre for International Health, University of Bergen, Bergen, Norway
| | - Hans J. Overgaard
- Norwegian University of Life Sciences, Ås, Norway
- Institut de Recherche pour le Développement (IRD), Maladies InfectieusesetVecteurs, Ecologie, Génétique, Evolution etContrôle (MIVEGEC), Montpellier, France
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
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Omondi D, Masiga DK, Ajamma YU, Fielding BC, Njoroge L, Villinger J. Unraveling Host-Vector-Arbovirus Interactions by Two-Gene High Resolution Melting Mosquito Bloodmeal Analysis in a Kenyan Wildlife-Livestock Interface. PLoS One 2015; 10:e0134375. [PMID: 26230507 PMCID: PMC4521840 DOI: 10.1371/journal.pone.0134375] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 07/08/2015] [Indexed: 11/23/2022] Open
Abstract
The blood-feeding patterns of mosquitoes are directly linked to the spread of pathogens that they transmit. Efficient identification of arthropod vector bloodmeal hosts can identify the diversity of vertebrate species potentially involved in disease transmission cycles. While molecular bloodmeal analyses rely on sequencing of cytochrome b (cyt b) or cytochrome oxidase 1 gene PCR products, recently developed bloodmeal host identification based on high resolution melting (HRM) analyses of cyt b PCR products is more cost-effective. To resolve the diverse vertebrate hosts that mosquitoes may potentially feed on in sub-Saharan Africa, we utilized HRM profiles of both cyt b and 16S ribosomal RNA genes. Among 445 blood-fed Aedeomyia, Aedes, Anopheles, Culex, Mansonia, and Mimomyia mosquitoes from Kenya’s Lake Victoria and Lake Baringo regions where many mosquito-transmitted pathogens are endemic, we identified 33 bloodmeal hosts including humans, eight domestic animal species, six peridomestic animal species and 18 wildlife species. This resolution of vertebrate host species was only possible by comparing profiles of both cyt b and 16S markers, as melting profiles of some pairs of species were similar for either marker but not both. We identified mixed bloodmeals in a Culex pipiens from Mbita that had fed on a goat and a human and in two Mansonia africana mosquitoes from Baringo that each had fed on a rodent (Arvicanthis niloticus) in addition to a human or baboon. We further detected Sindbis and Bunyamwera viruses in blood-fed mosquito homogenates by Vero cell culture and RT-PCR in Culex, Aedeomyia, Anopheles and Mansonia mosquitoes from Baringo that had fed on humans and livestock. The observed mosquito feeding on both arbovirus amplifying hosts (including sheep and goats) and possible arbovirus reservoirs (birds, porcupine, baboons, rodents) informs arbovirus disease epidemiology and vector control strategies.
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Affiliation(s)
- David Omondi
- Martin Lüscher Emerging Infectious Disease (ML-EID) Laboratory, International Centre for Insect Physiology and Ecology, P. O Box 30772-00100, Nairobi, Kenya
- Molecular Biology and Virology Laboratory, Department of Medical Biosciences, University of Western Cape, Private Bag X17, Bellville, 7535, South Africa
- Biochemistry and Molecular Biology Department, Egerton University, P.O Box 536, Egerton, 20115, Kenya
| | - Daniel K. Masiga
- Martin Lüscher Emerging Infectious Disease (ML-EID) Laboratory, International Centre for Insect Physiology and Ecology, P. O Box 30772-00100, Nairobi, Kenya
| | - Yvonne Ukamaka Ajamma
- Martin Lüscher Emerging Infectious Disease (ML-EID) Laboratory, International Centre for Insect Physiology and Ecology, P. O Box 30772-00100, Nairobi, Kenya
| | - Burtram C. Fielding
- Molecular Biology and Virology Laboratory, Department of Medical Biosciences, University of Western Cape, Private Bag X17, Bellville, 7535, South Africa
| | - Laban Njoroge
- Invertebrates Zoology Section, Zoology Department, National Museums of Kenya, P.O. Box 40658-00100, Nairobi, Kenya
| | - Jandouwe Villinger
- Martin Lüscher Emerging Infectious Disease (ML-EID) Laboratory, International Centre for Insect Physiology and Ecology, P. O Box 30772-00100, Nairobi, Kenya
- * E-mail:
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