West Nile Virus Detected In Mosquitoes And Birds

By: Katja Schulz

West Nile virus (WNv) has been documented in two separate samples collected in Laramie this week. The first positive sample was from a collection of mosquitoes trapped by City of Laramie crews and tested with the City’s Rapid Analyte Measurement Platform (RAMP). The sample was collected from the eastern portion of Laramie. The second positive was from an American Crow that was also collected within the City limits by Wyoming Game and Fish and tested by Wyoming State Veterinary Laboratory. Both samples showed high levels of WNv.

The rating of the Risk of West Nile virus infection continues to be rated at LEVEL 1 (LOW RISK) based on the Centers for Disease Control (CDC) guidelines for a phased response to WNv surveillance data. Currently virus activity is categorized as “Limited to sporadic activity in local mosquitoes and birds”. City of Laramie technicians have tested a total of 98 samples of Culex tarsalis mosquitoes throughout the summer season with a total of 3 positive samples. The positive crow sample is the first confirmed positive in avian species for this season.

Although total mosquito numbers are currently low, vector mosquitoes that can effectively transmit WNv make up a greater percentage of the mosquito population in late summer due to the overwintering and reproduction cycles of these species. Current surveillance locally shows very low numbers of vector mosquitoes being collected at trap locations throughout the Big Laramie River Basin. Even though the mosquito abundance is low, it only takes one mosquito bite to transmit this virus.

Mosquito control has suspended all fogging applications due to the low populations of vector mosquitoes.  A return to full residential fogging is not currently anticipated as it is likely that populations will continue to decrease, based on long term weather forecasts and historical data.  Mosquito control will continually evaluate the vector population and test for WNV through the fall, until freezing temperatures end the season. Citizens are asked to report dead birds to mosquito control for potential WNv testing.

Citizens are reminded that WNv can infect people of all ages but the elderly may be at the greatest risk for a serious infection. Locally, the mosquitoes that transmit WNv are most active after dusk and citizens should limit activities in areas with high mosquito populations during this time. Repairing screens, especially in sleeping rooms, and using personal protection such as proper clothing and insect repellent containing DEET can also reduce the risk.  Further Wyoming WNv information can be found on line at: the www.badskeeter.org or the Centers for Disease Control website: http://www.cdc.gov/westnile/index.html

Hotline information regarding chemical applications on City owned properties will be updated daily at 4pm. Call 721-5056 or click on the Mosquito and Chemical Application hotline tab on the City of Laramie home page. For further information contact Tyler Shelving, Acting Mosquito Control Crew Supervisor at 721-5258; tshelving@cityoflaramie.org or Todd Feezer Parks and Recreation Director at 721-5260; tfeezer@cityoflaramie.org.