Authors

M ADELEKE³; J Adeyemi¹; K Fasasi³; L Oforka⁴; A Adeogun²; G Olatunde³;  ¹ Federal University of Technology, Akure, Nigeria;  ² Nigerian Instituite of Medical Research, Nigeria;  ³ Osun State University, Nigeria;  ⁴ University of Lagos, Nigeria

Discussion

One of the major challenges facing malaria control today is the high spate of insecticide resistance in mosquito populations. The present study is therefore designed to investigate (i) the sibling composition of An. Gambiae complex using molecular techniques (ii) the susceptibility status of An. Gambiae complex to DDT and Deltamethrin at selected locations in Osun State, Nigeria. The larvae of An. Gambiae complex were collected from six selected towns, representing the three Senatorial geopolitical zones in Osun State. Two to three day old unfed female mosquitoes were subjected to bioassays using papers impregnated with 0.05% Deltametrin (pyrethroid) and 4% DDT (organochlorine) in accordance with WHO protocol. The mosquitoes were thereafter subjected to Polymerase Chain Reaction assay for molecular characterization of the sibling species. The results of the knockdown effects of the insecticides within 60 min of exposure ranged from 40-70% in mosquitoes exposed to Deltamethrin and 15-45% for the mosquitoes exposed to DDT across the locations. The post-exposure mortality caused by the two insecticides varied significantly; and mortality recorded in mosquitoes exposed to Deltamethrin was significantly higher than DDT (P>0.05) in all the study locations. The mortality recorded in mosquitoes exposed to DDT was less than 80% in all the locations. All the mosquitoes exposed to Deltamethrin also had less than 98% mortality except at a site where 100% mortality was recorded. Molecular identification showed that An. Gambiae s.s and An. arabiensis occurred at the study area. Therefore, the use of the two insecticides (Deltamethrin and DDT) for vector control and management in Osun State may not yield any appreciable results as the local populations of An.gambiae complex are virtually resistant to the two insecticides.