Composition and Diversity of Anopheles Species and Their Feeding Patterns in Nasarawa State, Nigeria: Implications for Malaria Vector Control

Abstract

Background: Anopheles mosquitoes transmit malaria and are major global disease vectors. Their varied feeding and resting behaviors make malaria control difficult and influence disease transmission. Aim: To investigate composition, abundance and feeding pattern of Anopheles species in Nasarawa State, Nigeria. Study Design: Three houses each were randomly selected in two communities for hourly collection of Anopheles species.   Place and Duration of Study: This study was conducted between March 2023 and February 2024 in two Local Government Areas of Nasarawa State, Nigeria. Methodology: Adult female Anopheles species were caught indoor and outdoor hourly from 6:00pm to 6:00am for three consecutive nights in each month in each of the three houses per sites using CDC light traps. Anopheles mosquitoes were morphologically identified using dissecting microscope. Species composition and abundance were compared using descriptive statistics and chi-square (χ²) tests at P<0.01, while feeding behaviour was assessed using Durbin Watson regression and t-tests. Results: Out of 3,826 female Anopheles species caught, 3,017(78.9%) were Anopheles gambiae s.l., 570(14.9%) Anopheles coustani, 154(4%) Anopheles funestus, and 85(2.2%) Anopheles pharoensis. An. gambiae was significantly (P<.01) more in Keffi, whereas An. coustani significantly (P<.01) predominated in Obi. No difference (P>.01) in An. funestus and An. pharoensis abundance in the two localities. An. gambiae’s abundance peaked during the wet season (July–September) and lowest in February. Anopheles species in the study areas were both exophagic and endophagic, biting late evening and early morning. Peak biting period of the four Anopheles species in the study areas was between 11:00 pm to 2:00 am.  An. coustani significantly (P=.05) bit outdoor while An. funestus and An. pharoensis significantly (P=.05) bit indoor. An. gambiae though bite more indoor but not significantly different (P=.05) with outdoor biting. Conclusion: Localised abundance and high outdoor biting activities of these Anopheles species underscores the importance of locality-specific vector control strategies that also address outdoor and peak biting hours because plasticity in mosquitoes’ behaviour reduces indoor-based control efficacy thereby sustaining malaria transmission despite conventional interventions.