The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. By this week, all regions across the prairies have now accumulated sufficient degree-day heat units for Culex tarsalis to develop to adult stages, if present in the region (Fig. 1).
As of August 15, 2021 (Fig. 1), C. tarsalis development has now reached the point that adults are predicted to be flying across all areas of the Canadian prairies. Outdoor enthusiasts falling within areas highlighted red OR in areas that have accumulated >400 degree-days for C. tarsalis to emerge should wear DEET to protect against WNV!
The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date August 13, 2021; retrieved August 19, 2021). The screenshot below (retrieved 19Aug2021) serves as a reference and reports one human case of WNV, two positive wild birds, and positive mosquito pools in Ontario.
Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (reporting date August 18, 2021; retrieved 19Aug2021) which reports 3 positive birds collected in both Ontario and Quebec.
Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.