Distribution of Anopheles Mosquito Species and Malaria Transmission Intensity in Ondo State, Southwest Nigeria

Understanding the entomological basis of malaria transmission is critical for the design of effective vector control interventions. This study assessed the distribution and relative abundance of Anopheles mosquito species and estimated malaria transmission intensity in selected communities of Ondo State, Southwest Nigeria. Adult mosquitoes were collected over three consecutive months using CDC light traps and pyrethrum spray catch methods in indoor and outdoor settings. A total of 1,240 Anopheles mosquitoes were morphologically identified, with Anopheles gambiae sensu lato accounting for 76.4 percent of the collection. Sporozoite rate, determined by ELISA, was 3.2 percent, yielding an entomological inoculation rate of 18.6 infectious bites per person per month. Transmission intensity was highest during the rainy season in communities with dense vegetation cover. Insecticide susceptibility testing showed reduced susceptibility to pyrethroids in field-collected mosquitoes, indicating emerging resistance. The study recommends updated resistance management strategies and regular entomological surveillance to guide malaria vector control programmes in Ondo State. Cross-referencing entomological data with clinical case records at nearby health facilities would further strengthen local transmission mapping. Keywords: Anopheles gambiae, malaria transmission, entomological inoculation rate, insecticide resistance, Ondo State.