Effect of environmental temperature on the susceptibility of Culex pipiens (Diptera: Culicidae) to Rift Valley Fever virus

Studies were conducted to determine the effect of environmental temperature on the susceptibility of Culex pipiens (L.) to Rift Valley fever (RVF) virus. Larval rearing temperature (13, 17, 19, or 26 degrees C) did not affect the susceptibility of adult female Cr. pipiens to infection with RVF virus. In contrast, the adult holding temperature after a viremic blood meal affected infection rates in females. Significantly fewer mosquitoes contained detectable virus when they were held at cooler temperatures, 13 degrees C (10%), 17 degrees C (20%), and 19 degrees C (41%) than at a warmer temperature, 28 degrees C (91%). For mosquitoes held at 13 degrees C and then switched to 26 degrees C, infection rates increased steadily with increased time at 26 degrees C. There was no effect on the ability to detect RVF virus in adult females that were subjected to cooler holding temperature (17 degrees C) after they were first held at warmer temperature (26 degrees C). The role of environmental temperature needs to be considered in studies on the epidemiology of arthropod-borne viruses.