Insecticide resistance profile and sex ratio of Culex quinquefasciatus in Umuahia, Abia State, Nigeria

Abstract

A vast majority of neglected tropical diseases such as lymphatic filariasis, Wuchereria bancrofti, avian malaria and a number of other viral diseases are vectored by Culex quinquefasciatus. This study was carried out to ascertain the insecticidal susceptibility status and sex ratio of Culex quinquefasciatus in Umuahia, Abia Sate, Nigeria, from November 2022 to February 2023. Larvae and pupae of Culex quinquefasciatus were sampled from different areas in Umuahia, and were conveyed in properly marked containers to the insectaria in the Entomology Unit of Michael Okpara University of Agriculture, Umudike. The mosquitoes were sustained and grown at a temperature of 26±3°C and relative humidity of 74±4% to adult stage for World Health Organization (WHO) kit bioassays. Four kinds, of WHO bioassay test papers treated with recommended diagnostic concentrations of 4% DDT (organochlorines), 0.75% permethrin (pyrethroids), 0.1% bendiocarb (carbamates) and 5% malathion (organophosphates) bought from the vector control unit of Universiti Sain Malaysia, were used for the bioassay. Records of knockdowns were taken at intervals of 0, 5, 10, 20, 30, 40, 50 and 60 minutes, and then maintained for 24 hours post exposure in 10% sugar solution. The percentage mortality of each insecticide after 24 hours was thereafter calculated and all the adult mosquitoes collected were sorted into male and female to determine the sex ratio. The result showed that Culex quinquefasciatus mosquitoes in the study area were resistant to DDT (organochlorines), permethrin (pyrethroids) and bendiocarb (carbamates) but susceptible to malathion (organophosphates). The sex ratio (1.5: 1) was male-biased which favoured mosquito vector control programme. This study showed that malathion was the insecticide of choice against Culex quinquefasciatus in the area. In view of the above, the use of botanicals is recommended for future vector control programmes because they are environmentally friendly and less likely to develop resistance.