A field bioassay for assessing ivermectin bio-efficacy in wild malaria vectors

Malaria Journal

Methodology

Lawrence Babu¹  Zedekiah Ondieki¹  Martha N. Muturi¹  Festus Yaah¹  Joseph Mwangangi¹  Haron Musani¹  Yvonne Kamau¹  Caroline Wanjiku¹  Marta F. Maia²  Mercy Tuwei³  Jonathan Karisa³  Simon Muriu³  Kelly M. Ominde³  Caroline Kiuru⁴  Carlos Chaccour⁵ 

[1] Department of Biosciences, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya;Department of Biosciences, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya;Centre for Global Health and Tropical Medicine and Nuffield Department of Medicine, University of Oxford, Oxford, UK;Department of Biosciences, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya;Department of Biological Sciences, and Pwani University Biosciences Research Centre, Pwani University, Kilifi, Kenya;ISGlobal, Barcelona, Spain;ISGlobal, Barcelona, Spain;Ciberinfec, Madrid, Spain;Faculty of Medicine, Universidad de Navarra, Pamplona, Spain;

关键词: Ivermectin;    Monitoring;    Vector control;    Bio-efficacy;    Anopheles gambiae;    Kenya;    Field bioassay;    Wild vectors;   

DOI  :  10.1186/s12936-023-04718-9

 received in 2023-03-06, accepted in 2023-09-13,  发布年份 2023

来源: Springer

【 摘 要 】

BackgroundIvermectin (IVM) mass drug administration is a candidate complementary malaria vector control tool. Ingestion of blood from IVM treated hosts results in reduced survival in mosquitoes. Estimating bio-efficacy of IVM on wild-caught mosquitoes requires they ingest the drug in a blood meal either through a membrane or direct feeding on a treated host. The latter, has ethical implications, and the former results in low feeding rates. Therefore, there is a need to develop a safe and effective method for IVM bio-efficacy monitoring in wild mosquitoes.MethodsInsectary-reared Anopheles gambiae s.s. were exposed to four IVM doses: 85, 64, 43, 21 ng/ml, and control group (0 ng/ml) in three different solutions: (i) blood, (ii) 10% glucose, (iii) four ratios (1:1, 1:2, 1:4, 1:8) of blood in 10% glucose, and fed through filter paper. Wild-caught An. gambiae s.l. were exposed to 85, 43 and 21 ng/ml IVM in blood and 1:4 ratio of blood-10% glucose mixture. Survival was monitored for 28 days and a pool of mosquitoes from each cohort sacrificed immediately after feeding and weighed to determine mean weight of each meal type.ResultsWhen administered in glucose solution, mosquitocidal effect of IVM was not comparable to the observed effects when similar concentrations were administered in blood. Equal concentrations of IVM administered in blood resulted in pronounced reductions in mosquito survival compared to glucose solution only. However, by adding small amounts of blood to glucose solution, mosquito mortality rates increased resulting in similar effects to what was observed during blood feeding.ConclusionBio-efficacy of ivermectin is strongly dependent on mode of drug delivery to the mosquito and likely influenced by digestive processes. The assay developed in this study is a good candidate for field-based bio-efficacy monitoring: wild mosquitoes readily feed on the solution, the assay can be standardized using pre-selected concentrations and by not involving treated blood hosts (human or animal) variation in individual pharmacokinetic profiles as well as ethical issues are bypassed. Meal volumes did not explain the difference in the lethality of IVM across the different meal types necessitating further research on the underlying mechanisms.

【 授权许可】

CC BY   
© BioMed Central Ltd., part of Springer Nature 2023

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