Susceptibility of Anopheles gambiae s.l., and Anopheles funestus s.l. to seven insecticides in southern Ethiopia

Abstract

Background: In Ethiopia, as the primary malaria vector control tools rely on the efficacy of insecticides, the susceptibility of malaria vectors should be monitored regularly. 

Methods: A standard WHO susceptibility test was used to test Anopheles gambiae s.l. (order Diptera, family Culicidae, Giles) from four sites and Anopheles funestus (order Diptera, family Culicidae, Giles) from one site in southern Ethiopia.

Results: Exposure to DDT, permethrin, and deltamethrin resulted in less than 95% knock down of mosquitoes one hour after exposure in all sites. Both species were resistant to DDT, permethrin, malathion, and deltamethrin in all sites tested. Conversely, both species were susceptible to fenitrothion in all sites tested.  An. gambiae s.l. was resistant to bendiocarb in the four sites, with mortalities between 92 and 97%, whereas An. funestus in the tested site was susceptible.  Similarly, An. funestus was susceptible to propoxur, and An. gambiae s.l. mortalities after exposure to propoxur were between 97 and 100%. 

Conclusions: The widespread resistance to pyrethroids is a concern for the efficacy of long-lasting insecticidal nets (LLINs), whereas the resistance to bendiocarb and incomplete mortality after exposure to propoxur present worrying signs for the efficacy of indoor residual spraying (IRS). There is a need for implementation of resistance management strategies to ensure continued gains in reducing malaria.