Species Composition and Plasmodium falciparum Infection Rates of Anopheles gambiae s.l. Mosquitoes in Six Localities of Kwara State, North Central, Nigeria

Abstract

Entomological data gathering is essential for monitoring malaria vector disease risks and selection of appropriate interventions for the protection of exposed human populations. This study assessed the relative abundance, species composition, and sporozoite infection rates of indoor resting An. gambiae s.l. malaria vectors in six communities across 3 Local Government Areas in Kwara State, Nigeria. Total number of mosquitoes collected by Pyrethrum Spray Catch method over a period of eighth months were correlated with rainfall values in the area. Plasmodium falciparum sporozoite infection rates and sibling species identification of collected An. gambiae s.l. mosquito samples were determined by ELISA and PCR respectively. Results showed a positive correlation (r = 0.639, p = 0.08) between rainfall and numbers of Anopheles mosquitoes in the study areas. The overall composition of the An. gambiae s.l sibling species in the collected samples from all the six communities showed the predominance of An. gambiae s.s 298 (75.3%) compared to An. coluzzii 94(23.7%) and An. arabiensis 4(1.0%). However, the sporozoite infection rate of An. coluzzii (22.3%) was higher compared to An. gambiae s.s (12.8%) and An. arabiensis (0%). Mean numbers of An. gambiae s.l mosquitoes were significantly higher in Ilorin west LGA compared to Asa (F = 17.81, P < 0.001) and Ilorin East LGAs (F = 22.81, P < 0.001). Sporozoite rates of both An. gambiae s.s and An. coluzzii sibling species were higher in Ilorin West communities (Aiyede 21%, Ogundele 32%) compared to Asa (Idi Emi 11.1%, Lasoju 5.1%) and Ilorin East (Oke Oyi 2.4%, Ote-efan 0%) communities. Prevalence of sporozoite-infected An. gambiae s.s and An. coluzzii indoors highlight the need for effective insecticide treated bed-nets interventions to protect the residents from malaria risks. Higher numbers of An. coluzzii in the swampy rice marshed Ilorin West LGA communities require larval source management as an additional strategy for effective malaria vector control.