Insecticide susceptibility level of Anopheles arabiensis in two agrodevelopment localities in eastern Ethiopia.

Anopheles arabiensis strains reared from larvae and pupae collected from two different localities, Metehara and Melka-Worer, eastern Ethiopia, were evaluated against three insecticides. Resistance states of adult females were determined using the WHO test kits under field condition. The insecticides used were WHO discriminating doses of 4% DDT, 0.75% permethrin and 0.1% propoxur. The study revealed that 42.5% of the An. arabiensis population was resistant to DDT in Melka-Worer while only 30% of the species was resistant in Metehara to the same insecticide. In Metehara, 25% of An. arabiensis was also resistant to permethrin while the population was highly susceptible to the insecticide in Melka-Worer. Propoxur, which was not evaluated in Melka-Worer, was highly toxic to An. arabiensis in Metehara. The knocked-down time (KD50) for permethrin was 14.5 and 12.5 minutes in Metehara and Melka-Worer, respectively. The implications of these findings are discussed.