Influence of meteorological variables on the abundance and distribution patterns of Anopheles mosquitoes in Epe and Orimedu, Lagos, Nigeria

Understanding the rainfall, relative humidity and temperature patterns and their correlations with larval abundance can inform planning timely and cost-effective malaria interventions. This study assessed the influence of meteorological variables on the abundance and distribution patterns of Anopheles larvae. Larval samples were collected once every month, for a period of 18 months, from forty-eight georeferenced sampling stations, selected by stratified systematic random sampling technique in Epe and Orimedu. Principal component analysis was used to assess the patterns of correlation between larval abundance and meteorological variables monthly, namely; rainfall, maximum- and minimum- temperatures and relative humidity. Highest Anopheles larval occurrence was observed in Feb, 2019 in Epe (1323) and in Orimedu (1178), which corresponded with a relatively low rainfall intensity (117 mm) and low relative humidity (76.4%). Lowest larval occurrence in Epe (250) was recorded in September, 2018 while the lowest was 195 in Orimedu recorded in August, 2018. The loading of the observatory variables in the PC plan shows that biplot axis one (F1) was mainly explained positively by maximum- (EV = 0.9) and minimum- temperatures (EV = 0.8), related to positive predictor of larval occurrence in Epe and Orimedu. Conversely, rainfall (EV = − 0.8) and relative humidity (EV = − 0.7) were related to negative predictor of larval occurrence in Epe and Orimedu, which may be due to the washing away and high mortality of larval instars by runoffs resulting from heavy and continuous rains. Anopheles larval occurrence is negatively influenced by intense rainfall, characteristic of peak period of rains in Epe and Orimedu.