Spatial Variation in Anopheles gambiae Complex Species Composition and Plasmodium Sporozoite Infection Among Indoor-Resting Mosquitoes in Rural Southwestern Nigeria
NJE Vol. 42(1) : 147-169, 2026
DOI.10.36108/NJE/6202/24.0111
Ibrahim, K.T.1, Ajayi, F.2, Oguayo, V.2, Noutcha, M.A.E.3, Anumudu, C.I.2
1Department of Zoology, Entomology Unit, University of Ibadan, Ibadan, Nigeria
Abstract
Continuous monitoring of mosquito vector distribution and dynamics is critical for effective malaria surveillance and control. However, current entomological data from rural southwestern Nigeria remain scarce. This study characterised indoor-resting mosquito populations and malaria transmission indices in two rural settlements in southwestern Nigeria during the 2022 rainy season. Indoor-resting mosquitoes were collected for three consecutive months in Igbo-Ora and Idere using pyrethrum spray catches and identified to species using standard morphological keys. Morphologically identified An. gambiae complex was subsequently differentiated into species by PCR–RFLP, and Plasmodium falciparum circumsporozoite protein was detected by ELISA. Among 739 mosquitoes collected, Anopheles accounted for 57.2%. Within the An. gambiae complex, An. gambiae sensu stricto comprised (56.0%) of typed specimens, An. coluzzii (31.2%), An. arabiensis (10.1%), and interspecific hybrids (2.7%), consistent with the heterogeneous sibling-species structure reported elsewhere in Nigeria. Sporozoite infection was detected only in An. coluzzii from Igbo-Ora (4.88%), yielding an overall infection rate of 0.47%, similar to low-to-moderate indoor infection levels observed in other Nigerian settings. Idere showed higher indoor-resting density (0.45 vs. 0.04 mosquitoes/room) and man-biting rate (0.07 vs. 0.01 bites/person/night) than Igbo-Ora, suggesting greater indoor vector–host contact, although such indices may fluctuate with season and local ecology. Marked spatial and temporal variation in species composition and abundance between the two communities mirrors patterns seen in broader Nigerian and West African surveys, where environmental and landscape factors drive fine-scale heterogeneity in vector distributions. These findings provide updated baseline data on Anopheles species assemblages and Plasmodium infection in rural southwestern Nigeria, underscoring the value of sustained entomological surveillance and site-specific, evidence-based vector control strategies tailored to local transmission dynamics
Keywords: Anopheles gambiae complex, malaria vectors, sporozoite infection, indoor residual density, southwestern Nigeria, entomological surveillance