Epidemiological risk factors: Understanding the effect of the environment on pathogen transmission by mosquitoes

For many years the influence of temperature variation and relative humidity on arbovirus transmission by mosquitoes has been overlooked in experimental studies. Recent empirical work however demonstrates that seasonal variation in daily temperature fluctuations can influence Aedes aegyptipopulation dynamics and dengue virus transmission. These studies reveal an interaction between the mean temperature of the daily exposure and the magnitude of fluctuations experienced by the mosquito. At low temperatures, large fluctuations appear to be beneficial for both the vector and the virus, by accelerating immature development and virus dissemination. At an intermediate temperature, the first evidence of virus dissemination is delayed 4 days, and immature development is extended by almost two days. At high temperatures however, small fluctuations have little to no effect on vector population dynamics or virus replication dynamics. Results demonstrate the potential for over- or under-estimating the risk of dengue virus transmission due to an incomplete understanding of the effect of realistic temperature fluctuations on vector-virus interactions in the field, particularly in areas with temperate climates.

The implications of these results extend beyond dengue virus transmission. Incorporating this methodology into ecological studies of other vector-pathogen interactions will be beneficial for improving our understanding of pathogen transmission in the field, and forecasting disease transmission risk.