Assessing insecticide susceptibility status of Anopheles mosquitoes in Gondar zuria district, Northwest Ethiopia

Insecticide-based vector control, which comprises the use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS), is the key method of malaria control in Ethiopia. However, its effectiveness is threatened as malaria vectors become resistant to insecticides. Thus, the aim of this study was to monitor the insecticide susceptibility status of malaria vectors. WHO susceptibility tests were used to detect knock-down and mortality rate in the wild malaria vectors collected in Gondar zuria woreda, Northwest Ethiopia. The WHO diagnostic doses of 0.75% permethrin, 0.05% deltamethrin, 0.05% alpha-cypermethrin, 0.1% propoxur and 0.25% pirimiphos-methyl were used. The major malaria vectors in Ethiopia, Anopheles gambiae s.l Anopheles funestus group, and Anopheles Pharoensis, were susceptible, to pirimiphos-methyl and propoxur. However, resistant to permethrin (mortality rate of 88.8%), alphacypermethrin (mortality rate of 67.5%), and deltamethrin (mortality rate of 73.8%). Although permethrin restoration was only 96% in permethrin resistant Anopheles mosquitoes, the efficacy of alphacypermethrin and deltamethrin was totally restored by pre-exposure to PBO. The susceptibility of malaria vectors to pirimiphos-methyl, propoxur, and PBO + pyrethroid insecticides is encouraging for successful malaria control. Further investigations are needed to better understand the molecular basis of pyrethroids insecticide resistant-malaria vectors.