West Nile Virus and Culex tarsalis (August 8, 2019; Wk 18)

West Nile Virus Risk –  Health Canada posts information related to West Nile Virus in Canada.  Health Canada also tracks West Nile Virus through human, mosquito, bird and horse surveillance.  Link here to access the most current weekly update (July 27, 2019). The screenshot below was retrieved 09Aug2019 as reference but access that information here.

The following is offered to predict when Culex tarsalis will begin to fly across the Canadian prairies (Fig. 1). Protect yourself by wearing DEET!  This week, regions most advanced in degree-day accumulations for Culex tarsalis, the vector for West Nile Virus, are shown in the map below.  As of July 28, 2019, areas highlighted orange are on the verge of approaching sufficient heat accumulation for mosquitoes to emerge.  Areas highlighted red in the map below should now have C. tarsalis in flight.

Figure 1. Predicted development of Culex tarsalis, across the Canadian prairies (as of August 5, 2019).

Once adults emerge, the following map demonstrates how quickly a Culex tarsalis mosquito carrying WNV can become fully infective (i.e., when it has accumulated 109 base 14.3° degree days) - it's a matter of days, depending on the region (Figure 2).  For example, as of August 8, 2019, Winnipeg MB was predicted to only take 16-18 days for C. tarsalis to become fully infective.