Influence of Climatic Factors on Aggression and Infectivity of Anopheles in the Districts the Indoor Residual Spray (IRS) in Northern Benin, West Africa

Background: Climate variability influence the diversity and abundance of malaria vectors and thereby on malaria transmission dynamics. Examine its effect on Anopheles parameters involved in transmission may predict the potential malaria hotspot as a right target for its control intervention strategies. Here, we investigated the influence of meteorological parameters on the aggressiveness and infectivity of Anopheles in two health districts zones where IRS has been extended in Northern Benin. Mosquito collections were carried out using human landing catches to evaluate rates of aggression and infectivity in twelve villages. Concomitantly, meteorological data from synoptic stations of Benin and neighbouring countries were collected in 2016-2017. The spatial distribution of infective bites of An. gambiae is characterized by an intense aggression in the rural villages of the study area. Analysis of variances showed significant HBR difference according to the period but not according to the locality. However, the same analysis carried out with the infectivity rate shows no significant difference according to the period and the locality. In addition, the number of infective bites per man per month is higher in August and October, and the climatic parameters that have mainly favoured aggression are wind speed, humidity, sunshine and temperature. Indeed, the peak of wind speed is concentrated around 1.2 km / h and in September (5 km / h) whereas the aggressiveness score of Anopheles in the region is greater than 10 infective bites per man a year. Malaria transmission by Anopheles is influenced by climatic factors. The climate observed in the districts where IRS was extended in northern Benin has a real impact on Anopheles density and weakens current and future vector control strategies. This could lead to a series of modifications observed in anopheline populations just after IRS implementation ranging from a tendency to exophagy, from a decrease in the rate of blood-feeding to changes in the time, and change in aggressiveness. These phenomena most likely contribute to the sustainability of malaria transmission despite vector control measures.