Effect of environmental temperature on the vector competence of Aedes fowleri for Rift Valley fever virus.

Studies were conducted to determine the effect of environmental temperature on the ability of Senegalese Aedes fowleri to transmit Rift Valley fever (RVF) virus. Temperatures tested included 17 degrees C, 28 degrees C and a cyclic (17-28 degrees C) regimen designed to mimic temperatures to which a mosquito might be exposed in October in southeastern Senegal. After per oral exposure, infection rates were similar (ca. 93%) for all three groups. However, RVF virus disseminated to the haemocoel more rapidly in mosquitoes held at higher temperatures, with peak dissemination rates (ca. 80%) reached at 11, 18 and greater than 42 days after the infectious blood meal for mosquitoes held at 28 degrees C, cyclic and 17 degrees C, respectively. Likewise, the time interval between ingestion of the viremic blood meal and the first transmission by bite was inversely related to environmental temperature, with the first transmission occurring at 11, 18 and 35 days for mosquitoes held at 28 degrees C, cyclic and 17 degrees C, respectively. After being transferred from 17 to 28 degrees C on days 7 or 14 after the infectious blood meal, mosquitoes rapidly developed a disseminated infection and transmitted virus by bite within 7 days. Environmental temperature significantly affected the vectorial capacity of A. fowleri for RVF virus, with transmission occurring earlier and at a higher rate in mosquitoes held at higher temperatures.