Impact of temperature on the transmission of West Nile virus by Culex mosquitoes

Principal Investigator: William Reisen

The current degree-day temperature model describing the impact of temperature on the duration of the extrinsic incubation period [EIP] of West Nile virus (WNV) in Culex tarsalis was estimated using the NY99 strain of virus and has not been validated using cycling temperatures or more recent viral strains. The proposed research tests our overarching hypothesis that temperature determines the duration of the EIP and therefore the rate of WNV amplification during late winter and spring by addressing three specific objectives: 1) compare the duration of the EIP for NY99, WN02 and a contemporary California WNV isolate at two constant temperatures, 2) if the viral isolates differ, revise the EIP model by estimating the duration of the EIP at 5 constant temperatures for the new WNV isolate, and 3) determine whether daily cycling temperature differs from constant temperature using vernal temperatures measured in California. This work is critical for assuring accurate temperature-related risk estimates in WNV response plans and the CalSurv Gateway, and for understanding how WNV may be transmitted during late winter and spring when most average temperatures remain below the replication threshold estimated from our previous study.