Effect of Environmental Temperature on the Ability of Culex tarsalis and Aedes taeniorhynchus (Diptera: Culicidae) to Transmit Rift Valley Fever Virus.

Rift Valley fever virus (RVFV) causes severe disease in domestic ungulates (cattle, goats, and sheep) and a febrile illness in humans (with ∼1% case fatality rate). This virus has been spreading geographically, and there is concern of it spreading to Europe or the Americas. Environmental temperature can significantly affect the ability of mosquitoes to transmit an arbovirus. However, these effects are not consistent among viruses or mosquito species. Therefore, we evaluated the effect of incubation temperatures ranging from 14°C to 30°C on infection and dissemination rates for Culex tarsalis and Aedes taeniorhynchus allowed to feed on hamsters infected with RVFV. Engorged mosquitoes were randomly allocated to cages and placed in incubators maintained at 14°C, 18°C, 22°C, 26°C, or 30°C. Although infection rates detected in Cx. tarsalis increased with increasing holding temperature, holding temperature had no effect on infection rates detected in Ae. taeniorhynchus. However, for both species, the percentage of mosquitoes with a disseminated infection after specific extrinsic incubation periods (4, 7, 10, 14, 17, or 21 days) increased with increasing incubation holding temperature, even after adjusting for the apparent increase in infection rate in Cx. tarsalis. The effects of environmental factors, such as ambient temperature, need to be taken into account when developing models for viral persistence and spread in nature.