Determining factors of the blood feeding behaviour of mosquito vectors of West Nile and Rift Valley fever viruses in Madagascar

In Madagascar, the health burdens caused by West Nile virus (WNV) and Rift Valley Fever virus (RVFV) vary across regions, likely resulting from the variations of their vector capacity. This study aimed to assess the degree of vector-hots contact and to develop statistical models to identify factors influencing host preferences. Bimonthly mosquito collections were performed in 25 sites of Madagascar from February to October 2019. Engorged mosquitoes were collected from indoors and outdoors resting locations within each site. Blood meal identification was performed using host-specific PCRs. Generalised linear models were developed to explain host preferences of the two most abundant species. The origin of the blood meal of 1,177 engorged females belonging to ten species was analysed. Human and cattle were the dominant vertebrate hosts identified (respectively 44.86% and 44.52%), and pigs were rarely detected (< 1%). Models were developed for Culex antennatus and Culex quinquefasciatus. For these two species, host preference was driven by climatic and environmental factors, type of habitat, indoor/outdoor location, and number of available vertebrate hosts. This study provides an essential step towards an evidence-based determination of arbovirus transmission risk and suggests to explore the use of other tools to supplement indoor vector control in Madagascar.