Insecticide susceptibility status of Anopheles stephensi against novel insecticides in Eastern Ethiopia

Anopheles stephensiwas known to be local malaria vector in South East Asia but recently found expanding to the horn of Africa including urban areas of Ethiopia. Recent studies indicated that An. stephensihave high level of insecticide resistance to pyrethroid (Deltamethrin, permethrin and alpha-cypermethrin), Carbamates (Bendiocarb and Propoxur) and organophosphates (pirimiphos-methyl). The aim, of this study was to evaluate the susceptibility of An. stephensi from Diredawa against broflanilide, chlorfenapyr, clothianidin and pyriproxyfen.

A standard diagnostic doses of broflanilide, chlorfenapyr, clothianidin and pyriproxyfen were tested, using the revised WHO bottle bioassay test protocol, against wild adult An. stephensieared from larval collections from urban artificial larval habitats in Dire Dawa.

The 60 minutes knock down result indicated 85%, 76% and 14% against brofilanilide, clothianidin and clorfenapyr respectively. No KD was observed in controls and PPF. Complete mortality of An.stephensiat 24 hours was observed against broflanilide (9ug/bottle) and clothiandin (10ug/bottle). Also 66% mortality at 24 h and 100% mortality at 48 h post exposure against clorfenapyr (100ug/bottle) were observed. In case of PPF (100ug/bottle), no mortality at 24 h, 11% at 48 h. and 15% at 72 h were recorded and no mortality in all controls.In addition, 100% of oviposition were observed in controls and no oviposition were observed in PPF exposed mosquitoes. These results suggest that all three types of insecticides namely: Broflanilide, Chlorfenapyr and Clothianidin showed higher mortality than pyriproxyfen.

Full susceptibility to the three novel insecticides were observed and full oviposition inhibition were observed in wild reared larvae An. stephensi exposed to PPF. Therefore, this study recommends using these novel insecticides to control An. stephensi in Ethiopia.