Susceptibility status of mosquitoes (Diptera: Culicidae) to Malathion in Lagos, Nigeria

Abstract

Mosquitoes are major vectors of infectious diseases transmitting malaria,  lymphatic filariasis, yellow fever, dengue fever, zika and chikungunya virus.  Resistance to DDT, pyrethriods and carbamates has been reported to different mosquito species in Nigeria. This investigation was carried out to determine the susceptibility status of mosquitoes in Lagos State, Nigeria to malathion. Mosquito larva were collected from four different Local Government Areas of Lagos, and reared to adult. Female adult mosquitoes were exposed to 5 % malathion insecticide test papers using WHO standard procedures and kits. Species identification was done using PCR assay. Suspected resistance was observed in Cx. quinquefasciatus from Kosofe and Alimosho with 24 hour mortality of 96 % and 95 % respectively. Other mosquito species and Cx. quinquefasciatus from Badagry and  Ibeju-Lekki were fully susceptible 24 hours post exposure period. KDT50 and KDT95 for An. gambiae s.s ranges from 14.6 – 25.1 and 23.7 – 51.5 minutes respectively for all the location, KDT50 and KDT95 for Ae. aegypti ranges from 24.8 – 27.8 and 44.8 – 62.5 minutes respectively for all the location and KDT50 and KDT95 for Cx. quinquefasciatus ranges from 21.5 – 37.8 and 41.5 – 77.7 minutes respectively for all the location. The relatively high values of KDT50 and KDT95 in all assayed mosquito species call for urgent attention and may indicate the gradual development of malathion resistance to different mosquito species in Lagos. Regular insecticide resistance monitoring is needed and the indiscriminate use of unapproved organophosphate insecticides to be discouraged to forestall the development of malathion resistance in mosquitoes.

Keywords: Mosquitoes, Insecticide resistance, Malathion, Organophosphates, Infectious diseases