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Host identification, environmental and climatic variables associated to host-feeding patterns of mosquito vectors of West Nile and Rift Valley fever viruses in Madagascar
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International audience. The burdens of West Nile and Rift Valley Fever viruses vary across Madagascar, probably resulting from heterogenous abundance of mosquito vector species and variations in the level of vector-host contacts. Here we explore the association of host, climatic and environmental factors with mosquito feeding behaviour. Bimonthly mosquito collections were performed in 24 districts of Madagascar from February to October 2019. Engorged mosquitoes were collected indoors after indoor pyrethrum spraying (IPSCs) and outdoors using Muirhead-Thomson pit traps (MTPTs). Blood meal identification was performed using PCRs. For the two predominant mosquito species, beta regression models were developed using four blood indices (BI) corresponding to human (HBI), cattle (CaBI), bird (BiBI) and small ruminants (SRBI) as response variables. Twelve variables including seasonality, average number of vertebrate hosts per house, climatic and environmental factors were included as explanatory variables. In MTPTs, origin of the blood meals were identified in 770 females of 843 females tested. In IPSCs, they were identified in 297 females of 334 females tested. Human was the dominant vertebrate host identified (44.86%), followed by cattle (44.52%) and Galliformes (25.53%). Blood meals from Passeriformes and pigs were rarely detected (<1%). Blood indices of Culex antennatus and Culex quinquefasciatus (two predominant species) varied in time and space (p<0.05), and were correlated to the collection method used (p<0.05). Significant associations between the mosquito blood indices and explanatory variables were observed only for Cx. antennatus : (i) HBI and the average number of humans per house [Odds Ratio =2.36], (ii) CaBI and the outdoor resting location [OR =0.28], the precipitation [OR= 1.03] and relative humidity [OR =0.93]. (iii) BiBI and the type of house [OR= 3.89] and the number of humans per house [OR= 0.41]. The different results obtained from Cx. antennatus and Cx. quinquefasciatus demonstrate differences in biological and ecological traits between mosquito species.
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