Variations in household microclimate affect outdoor-biting

Mosquito behaviours including the degree to which they bite Background inside houses or outside is a crucial determinant of human exposure to malaria. Whilst seasonality in mosquito vector abundance is well documented, much less is known about the impact of climate on mosquito behaviour. We investigated how variations in household microclimate affect outdoor-biting by malaria vectors, and . Anopheles arabiensis Anopheles funestus : Mosquitoes were sampled indoors and outdoors weekly using Methods human landing catches at eight households in four villages in south-eastern Tanzania, resulting in 616 trap-nights over 12 months. Daily temperature, relative humidity and rainfall were recorded. Generalized additive mixed models (GAMMs) were used to test associations between mosquito abundance and the microclimatic conditions. Generalized linear mixed models (GLMMs) were used to investigate the influence of microclimatic conditions on the tendency of vectors to bite outdoors (proportion of outdoor biting). : abundance peaked during high rainfall months Results An. arabiensis (February-May), whilst density remained stable into the dry An. funestus season (May-August) Across the range of observed household temperatures, . a rise of 1 C marginally increased nightly abundance (~11%), An. arabiensis but more prominently increased abundance (~66%). The An. funestus abundance of and showed strong positive An. arabiensis An. funestus associations with time-lagged rainfall (2-3 and 3-4 weeks before sampling). The degree of outdoor biting in was significantly associated with the An. arabiensis relative temperature difference between indoor and outdoor environments, with exophily increasing as temperature inside houses became relatively warmer. The exophily of did not vary with temperature differences. An. funestus : This study demonstrates that malaria vector shifts Conclusions An. arabiensis the location of its biting from indoors to outdoors in association with relative differences in microclimatic conditions. These environmental impacts could give rise to seasonal variation in mosquito biting behaviour and degree of protection provided by indoor-based vector control strategies. 1,2 1,3 2