Repellent and Larvicidal Effects of Some Indigenous Plants in Abia State, Nigeria Against Female Anopheles gambiae

This study investigated the repellent and larvicidal activities of ethanol leaf extracts from three plants, Azadirachta indica, Carica papaya and Annona muricata, against female Anopheles gambiae mosquitoes with the aim of identifying effective plant-based alternatives for malaria vector control. Adult mosquitoes were collected from Garki Market in Okigwe, Imo State, Nigeria using an aspirator and transported to the laboratory for identification and rearing. Female An. gambiae mosquitoes were isolated and maintained under standard insectary conditions for reproduction. Third instar larvae were used for larvicidal assays, while fourth instar larvae were reared to adulthood for repellency tests. Repellency was assessed using the WHO Arm-in-Cage protocol. The ethanol leaf extracts of the three plant species were tested at concentrations of 0%, 2.5%, 5%, 10%, 15%, and 20%. All three plant extracts demonstrated significant, dose-dependent repellent and larvicidal effects. At 20% concentration, A. muricata showed the highest repellency (96.97%), followed by A. indica (95.15%) and C. papaya (89.09%). A strong negative correlation was observed between extract concentration and mosquito landings (r = -0.978, -0.949, and -0.981, respectively). Complete larval mortality (100%) was achieved at concentrations above 10% for A. indica and C. papaya, and above 5% for A. muricata. Phytochemical analysis revealed a high presence of flavonoids in all three species, suggesting a potential link to their bioactivity. These findings highlight the potential of these plant extracts as environmentally friendly and accessible alternatives for malaria vector control, particularly in resource-limited settings.