Phenotypic Physiognomies and Malaria Vectors KDT to Certain Insecticides in Some Populations of Anambra State, Southeast Nigeria

Background:Malaria which is a disease that istransferred by disease-ridden female Anopheles mosquitoes remains a foremostunrestricted health problem in Nigeria particularly and the world at large. Obviously, innumerable classes of insecticides have frolickedsubstantialstarring role in the management and elimination of malaria by confronting the malaria vectors. Regrettably, the achievement of the use of insecticides in the effective and efficient control of malaria vectors is endangered by the development of resistance to the insecticides in malaria-endemic areas such as Anambra State, Southeast part of Nigeria. The current study was hence aimed at determining the phenotypic physiognomies and subsequent knockdown times (KDT) of the vectors to certain insecticides in some communities ofAnambra State, Southeast Nigeriawhose results will beused for effective management and control. Methods:Mosquitoe larval samples were collected from diverse habitats using the dipper method and reared to adults for susceptibility test using the test-kits recommended by World Health Organization (WHO). During the exposure of the vectors to insecticides, records were taken of the number of mosquitoes knocked down intermittently after 10, 15, 20, 30, 40, 50 60 minutes and 24 hours post exposure. One-way analysis of variance (ANOVA) and log-probit regression analysis were used to calculate the knockdown times (KDT50, KDT90 and KDT95) whereasmultiple comparisonsof mortality and knockdown rate were done using the least significant difference (LSD) test. Results: The result disclosed that Anopheles gambiaewith a prevalence of (54.2%) was the leading vector, tailed by Anopheles coluzziiwhich recoreded (45.8%) in the survey area. Percentage mortality of Anopheles gambiaes.l. after 24 hours was 100% in Malathion (Organophosphate) and Bendiocarb (Carbamate) in all the study areas. Mortality rate in Permethrin (Pyrethroid) ranged from 62%-65% and for Deltamethrin (Pyrethroid) was 54%-63% across the study areas. In Awka South LGA, knockdown times (KDT50, KDT90 and KDT95) were: 170 minutes, 396.5 minutes, and 501 minutes, respectively. While in Awka North LGA, the (KDT50, KDT90 and KDT95) were: 199 minutes, 478 minutes and 602 minutes, whereas in Njikoka LGA, the (KDT50, KDT90 and KDT95) were: 186 minutes, 436.5 minutes and 562.3 minutes, respectively. Conclusion:High knockdown times to Malathion and Bendiocarbinsecticides was repeatedlydetected in the study areas. This is a pointer that the use of Pyrethroids is efficient for insecticidal control of malaria vectors. Nevertheless, low knockdown times to Deltamethrin and Permethrin is a plank in the fight against the vectors. To that effect, there is an imperativerequirement for implementation of resistance management approaches alongside insecticide resistance monitoring in the Stateto avert the increasing resistance rate as was detected in the study.