Comparative Efficacy of Selected Insecticides Against Adult Mosquitoes of Public Health Importance

Abstract

Insecticide resistance is an increasing challenge to effective mosquito control and poses a serious threat to vector-borne disease management. The present study was conducted during 2024 at the National Agricultural Research Centre (NARC), Islamabad, to assess the susceptibility of selected mosquito populations from Khyber Pakhtunkhwa, Pakistan, to commonly used adulticides. Anopheles stephensi, Culex quinquefasciatus, and Aedes aegypti populations were evaluated using WHO diagnostic concentrations of DDT (4%), malathion (5%), and deltamethrin (0.05%). Marked differences in mortality were observed among mosquito populations. An. stephensi from Peshawar showed complete susceptibility, with 100% mortality against all three insecticides. Similarly, Ae. aegypti from Peshawar exhibited high susceptibility, with mortality ranging from 98% to 100%. In contrast, An. stephensi from Charsadda showed substantially reduced mortality to DDT (26.7%), malathion (19.2%), and deltamethrin (79.4%), indicating resistance. Cx. quinquefasciatus from Nowshera also demonstrated pronounced resistance to DDT (29.5%) and malathion (4.0%), while deltamethrin produced comparatively higher mortality (84.3%), requiring verification. Overall, the findings demonstrate considerable geographical and species-specific variation in insecticide susceptibility. The observed resistance, particularly to DDT and malathion, highlights the need for continuous insecticide-resistance surveillance, rational insecticide selection, and implementation of resistance-management strategies. These findings provide useful baseline information for improving mosquito-control programmes in Khyber Pakhtunkhwa and support the need for further investigation of the biochemical and molecular mechanisms underlying insecticide resistance.