Impacts of ivermectin mass drug administration for onchocerciasis on mosquito populations of Ogun state, Nigeria

Olaitan Olamide Omitola,Adedotun Ayodeji Bayegun,Cynthia Uchechukwu Umunnakwe,Uwem Friday Ekpo,Samuel Akinjide Anifowose,Hammed Oladeji Mogaji,Sammy Olufemi Sam-Wobo,Adebola Adedoyin Osipitan,Simon Nnayere Odoemene,Taiwo Sam Awolola,Akinola Stephen Oluwole

doi:10.1186/s13071-021-04716-3

Olaitan Olamide Omitola, Adedotun Ayodeji Bayegun + Show 9 more

Open Access

https://doi.org/10.1186/s13071-021-04716-3

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Abstract

BackgroundThe impact of single-dose mass drug administration (MDA) of ivermectin for onchocerciasis on mosquito populations was investigated in Ogun State, Nigeria.MethodsIndoor and outdoor collection of mosquitoes was carried out in two intervention (IC) and two control communities (CC) at three different periods: pre-MDA (baseline), 2–3 days after MDA and 13–14 days after MDA. The density and parity rate of female Anopheles and Culex mosquitoes were determined and compared. Environmental and climatic data of study locations were obtained to perform generalized linear model analysis.ResultsA total of 1399 female mosquitoes were collected, including 1227 Anopheles and 172 Culex mosquitoes. There was a similar magnitude of reduction in the indoor density of Anopheles by 29% in the IC and CC 2–3 days post-MDA but the reduction in indoor parity rate was significantly higher (p = 0.021) in the IC, reducing by more than 50%. In the IC, observation of a significant reduction at 2–3 days post-MDA was consistent for both the indoor density (1.43 to 1.02) and indoor parity rate (95.35% to 44.26%) of Anopheles mosquitoes. The indoor parity rate of Anopheles remained significantly reduced (75.86%) 13–14 post-MDA. On the other hand, the indoor density of Culex increased from 0.07 to 0.10 at 2–3 days post-MDA while the indoor parity rate of Culex did not change. The outdoor density of Anopheles in the IC increased (p = 0.394) from 0.58 to 0.90 at 2–3 days post-MDA; a similar observation was consistent for the outdoor density (2.83 to 3.90) and outdoor parity rate (70.59% to 97.44%) of Culex, while the outdoor parity rate of Anopheles reduced from 85.71 to 66.67% at 2–3 days post-MDA. A generalized linear model showed that ivermectin MDA significantly caused a reduction in both the indoor density (p < 0.001) and indoor parity rate (p = 0.003) of Anopheles in the IC.ConclusionIvermectin MDA resulted in the reduction of both the survival and density of Anopheles mosquitoes. This has strong implications for malaria transmission, which depends strongly on vector survival.Graphical abstract

Highlights

Mosquitoes alone account for 17% of the estimated global burden of infectious diseases, and every year, malaria which is transmitted by the Anopheles mosquito, causes the deaths of more than 400,000 people and incapacitatesOmitola et al Parasites Vectors (2021) 14:212 another 200 million for days [1]
We investigated the impacts of the annual round of ivermectin mass drug administration (MDA), used for the control of onchocerciasis and lymphatic filariasis (LF), on local mosquito vector populations in the communities of Odeda local government area (LGA) in Ogun State, Nigeria
The abundance of Anopheles mosquitoes was significantly lower in the intervention communities where the annual ivermectin MDA round has been ongoing for a long period

Summary

Introduction

Mosquitoes alone account for 17% of the estimated global burden of infectious diseases, and every year, malaria which is transmitted by the Anopheles mosquito, causes the deaths of more than 400,000 people and incapacitatesOmitola et al Parasites Vectors (2021) 14:212 another 200 million for days [1]. Residual transmission occurs when malaria continues to be transmitted, despite the effective implementation of available vector control tools, as a result of mosquitoes adapted to biting outside the time of the day when LLINs and indoor residual spraying can protect people. Ivermectin is a systemic endectocide, which, when administered to humans or animals, is toxic to mosquitoes that feed on the treated vertebrate host. This provides an opportunity to eliminate mosquitoes that may escape or survive existing vector control interventions since all female mosquitoes must obtain blood meals for the development of their eggs [3]. The impact of single-dose mass drug administration (MDA) of ivermectin for onchocerciasis on mos‐ quito populations was investigated in Ogun State, Nigeria

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