Infection of the malaria vector Anopheles coluzzii with the entomopathogenic bacteria Chromobacterium anophelis sp. nov. IRSSSOUMB001 reduces larval survival and adult reproductive potential.

Background: Vector control tools are urgently needed to control malaria transmission in Africa. A native strain of Chromobacterium sp. from Burkina Faso was recently isolated and preliminarily named Chromobacterium anophelis sp. nov. IRSSSOUMB001. In bioassays, this bacterium showed a promising virulence against adult mosquitoes and reduces their blood feeding propensity and fecundity. The current study assessed the entomopathogenic effects of C. anophelis IRSSSOUMB001 on larval stages of mosquitoes, as well as its impacts on infected mosquitoes reproductive capacity and trans-generational effects.

Methods: Virulence on larvae and interference with insemination were assayed by co-incubation with C. anophelis IRSSSOUMB001 at a range of 10 to 10 cfu/ml. Trans-generational effects were determined by measuring body size differences of progeny from infected vs. uninfected parent mosquitoes using wing size as a proxy.

Results: Chromobacterium anophelis IRSSSOUMB001 killed larvae of the pyrethroid-resistant Anopheles coluzzii with LT of ~ 1.75 ± 0.14 days at 10 cfu/ml in larval breeding trays. Reproductive success was reduced as a measure of insemination rate from 95 ± 1.99% to 21 ± 3.76% for the infected females. There was a difference in wing sizes between control and infected mosquito offsprings from 2.55 ± 0.17 mm to 2.1 ± 0.21 mm in infected females, and from 2.43 ± 0.13 mm to 1.99 ± 0.15 mm in infected males.

Conclusions: This study showed that C. anophelis IRSSSOUMB001 was highly virulent against larvae of insecticide-resistant Anopheles coluzzii, and reduced both mosquito reproduction capacity and offspring fitness. Additional laboratory, field, safety and social acceptance studies are needed to draw firm conclusions about the practical utility of this bacterial strain for malaria vector control.