Does Ivermectin impair Anopheles mosquitoes’ attractiveness toward treated cattle under field and laboratory conditions?

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Zela, Lamidi | Pooda, Sié Hermann | Porciani, Angelique | Sagna, André, Barembaye | Bandaogo, Abdoul Malik | Kambou, Ramzy, A. N. | Somé, Anyirekun, Fabrice | Roberge, Christophe | Belem, Adrien, M. G. | Dabiré, Roch Kounbobr | Mouline, Karine

Edité par CCSD -

International audience. Introduction : The administration of ivermectin (IVM) to humans or cattle is viewed as a promising complementary tool to control malaria vectors. However, potential modification of treated hosts’ attractiveness to mosquitoes owing to IVM metabolization has not been studied. This study aimed to investigate whether the malaria vector An. coluzzii was more attracted to IVM-treated cattle compared to control groups.Methods : A two-arm study was designed using 8 calves: 4 controls and 4 treated with a long-acting ivermectin formulation at a dose of 1mg/kg (3-4 months efficacy, IMPACT project). The calves were exposed to wild mosquitoes at t=2 days, 1-, 2-, 3-, and 4-month post-treatments, under nets in the field (Bama, Burkina Faso) and to An. coluzzii (lab colony) using a dual-choice olfactometer in the laboratory. In field experiment, trapped wild mosquitoes were counted and identified into species. In laboratory experiment, female An. coluzzii were released into an olfactometer, and activated females were counted according to their preference for treated or control calves.Results : A total of 181,696 mosquitoes was collected in field experiments, of which 70% were Culex, 27.3% Anopheles, and 2.7% Mansonia. IVM treatments did not influence mosquito attractiveness (X22=0.8791; P=0.3484) when all mosquitoes were taken together. However, IVM-treated calves were more attracted by Anopheles mosquitoes than controls, but this was only significant at month 4 post-treatment (Z=0.584; P =0.001). An. coluzzii tended to be more trapped around treated than control calves for all timepoints, but this difference was not significant. At the laboratory, dual choice-tests on An. coluzzii colony showed similar attractiveness regardless of cattle treatments (Z=0.215; P=0.83).Conclusions : IVM seemed to increase Anopheles mosquitoes, including An. coluzzii attractiveness toward treated calves in the field, but not in the laboratory. Further studies are needed to decipher the main odor molecules driving this attractiveness toward IVM-treated calves.

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