Infection of the malaria vector Anopheles coluzzii with the entomopathogenic bacteria Chromobacterium sp. Burkina (C.sp_B) highly reduces larval survival and adult reproductive potentials

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Abstract BackgroundAdditional vector control tools are urgently needed to control malaria transmission in Africa. A native strain of Chromobacterium sp. from Burkina Faso (C.sp_B) was recently characterized. In bioassays, this bacterium showed a promising virulence and against adult mosquitoes and reduces their blood feeding propensity and fecundity. The current study aimed to assess entomopathogenic effects of C.sp_B on larval stages of mosquitoes, its impacts on infected mosquitoes reproductive capacity and their offsprings.MethodsThree different types of bioassays were performed in laboratory. The first bioassay aimed to evaluate the impact of C.sp_B infection on mosquito larvae survival using different bacterial concentrations. The second bioassay wanted to access the effect of C.sp_B infection on female insemination rates. The third bioassay investigated the impact of a non-lethal exposure of C.sp_B to parent mosquitoes on the body size of its offsprings. During bioassays mosquitoes were infected through the well-established systems of larvicidal procedure and through cotton ball soaked with 6% glucose containing. ResultsBurkina Faso native strain of Chromobacterium sp (C.sp_B). killed larvae of the pyrethroid resistant Anopheles coluzzii with LT80 of ~0.60 ± 0.03 days at 108 CFU/ml at larval breeding trays. Interestingly, this bacterium had important effects on mosquito reproductive success by reducing the insemination rate of uninfected females from 95 ±1.99 % to 21 ±3.76 % for the infected females. Moreover, C.sp_B considerably reduced the wing size of offspring from infected parents compared to uninfected parents. Within females, the wing size was 2104.157 ± 20.89 mm and 2547.569 ± 17.08 mm for offspring from C.sp_B. infected females and uninfected females respectively. For males the size of wings were respectively, 1991.059 ± 14.98 mm and 2436.220 ± 13.52 mm for offspring from C.sp_B infected males and uninfected males respectivelyConclusionThis study showed that the Burkina Faso Chromobacterium sp strain (C.sp_B) was highly virulent against larvae of insecticide-resistant An. coluzzii, and reduced both mosquito reproduction capacity and offspring fitness. However, additional lab, field, safety and social acceptance studies are needed to withdraw more conclusions about the practical utility of this promising bacterial strain for malaria vector control.

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