Malaria Vector Composition, Abundance, and Plasmodium Infection Rates in Rural Southwestern Nigeria: Implications for Targeted Control Strategies.

Background: Malaria remains a major public health concern in Nigeria, particularly in rural communities where environmental and socio-demographic factors drive sustained transmission. Understanding mosquito species composition, abundance, and infection rates is essential for effective vector control interventions.

Methods: This study investigated malaria vector diversity and transmission dynamics in two rural communities, Igbo-Ora and Idere, in southwestern Nigeria. Indoor-resting mosquitoes were collected monthly during the 2022 rainy season using pyrethroid spray collection methods. Collected specimens were morphologically and molecularly identified, and circumsporozoite protein (CSP) ELISA was performed to detect Plasmodium infection.

Results: A total of 739 mosquitoes belonging to three genera (Anopheles, Culex, and Aedes) were collected, with Anopheles species being the most abundant (57.2%). Molecular identification of the Anopheles gambiae complex revealed three sibling species, An. gambiae s.s. (56%), An. coluzzii (31.2%), and An. arabiensis (10.1%), with hybrid forms also detected. An. gambiae s.l. was the primary malaria vector, comprising 70.4% of the Anopheles mosquitoes. Vector density varied between locations, with higher indoor resting density (IRD: 0.45) and man-biting rate (MBR: 0.11) in Idere compared to Igbo-Ora (IRD: 0.04; MBR: 0.01). Sporozoite infection rates were low, with only two An. coluzzii testing positive for Plasmodium falciparum CSP antigen in Igbo-Ora (2.53% infection rate).

Conclusion: The findings highlight the ecological factors influencing malaria vector distribution and transmission dynamics in rural Nigeria. The dominance of An. gambiae s.l. and localized differences in vector abundance emphasize the need for site-specific, adaptive vector control strategies. Continuous surveillance is essential, particularly in the context of insecticide resistance and evolving vector behavior, to enhance malaria intervention programs in endemic regions.