Efficacy of vector control tools against malaria-infected mosquitoes

Abstract

Within mosquito vector populations, infectious mosquitoes are the ones completing the transmission of pathogens to susceptible hosts and they are, consequently, of great epidemiological interest. Mosquito infection by malaria parasites has been shown to affect several traits of mosquito physiology and behavior, and could interplay with the efficacy of control tools. In this study, we evaluated, in pyrethroid resistant Anopheles gambiae, the effect of mosquito infection with the human malaria parasite Plasmodium falciparum on the efficacy of nets treated with either the insecticide deltamethrin or the repellent DEET, measuring (i) mosquito success to pass through the net, (ii) blood-feeding on a host and (iii) chemicals-induced mortality. Infection of mosquitoes at non-infectious stage did not affect their success to pass through the net, to blood-feed, nor chemicals-induced mortality. At infectious stage, depending on replicates, infected mosquitoes had higher mortality rates than uninfected mosquitoes, with stronger effect in presence of DEET. This data evidenced a cost of infection on mosquito survival at transmissible stages of infection, which could have significant consequences for both malaria epidemiology and vector control. This stresses the need for understanding the combined effects of insecticide resistance and infection on the efficacy on control tools.

Figure 1

Passing rate through deltamethrin-impregnated nets (A), blood-feeding (B) and mortality associated (C). Blood-feeding was calculated for females that successfully passed through the impregnated net. Hatched bars show infected females, and full bars show non – infected ones. I = Infected, NI = Non-Infected. Results are presented as mean ± standard error (s.e). Different letters indicate significant differences (post hoc chi-squared tests with a Tukey correction).

Figure 2

Passing rate through DEET-impregnated nets (A), blood-feeding (B) and mortality (C). Blood-feeding was calculated for females that successfully passed through the impregnated net. Hatched bars show infected females, and full bars show non – infected ones. I = Infected, NI = Non-Infected. Results are presented as mean ± standard error (s.e). Different letters indicate significant differences (post hoc chi-squared tests with a Tukey correction).