West Nile virus detected in Saskatchewan wild birds
CWHC Western/Northern has detected West Nile virus in six dead wild birds from Saskatoon and Outlook, Saskatchewan.
The first of these, an American Crow, was found sick in early July in a Saskatoon neighborhood. The bird was unable to walk or fly and died shortly after being taken to local wildlife rehabilitators. CWHC Western/Northern received the bird and collected swabs for avian influenza and West Nile virus testing. Avian influenza was not detected but the sample tested positive for West Nile virus. Another crow from Saskatoon tested positive for West Nile virus about a week later after being found with similar signs of illness. Further testing is being done to determine whether infection with the virus was the main cause of death for the crows.
Four birds also tested positive from the town of Outlook, located about 80km south of Saskatoon. Three crows and a Black-billed Magpie were found dead in late June and submitted to CWHC Western/Northern prior to the start of routine seasonal testing. Although the birds were not initially tested for West Nile virus, they were later tested after signs of infection were seen in the tissues.
The presence of West Nile virus in wild bird populations indicates that the virus is circulating in these areas of the province despite all mosquito pools testing negative so far.
West Nile virus infects many bird species and can cause illness and death in corvid species (crows, magpies, etc.) and some birds of prey (hawks, owls, etc). Mosquitos feed on infected birds and transmit the virus to other birds as well as some mammal species, including humans and horses. The virus can cause severe illness in a small percentage of human cases. As West Nile virus depends on mosquito populations, specifically Culex species for transmission, the presence and timing of the virus in Saskatchewan changes from year to year and is impacted by changes in climate and weather patterns.
Saskatchewan Ministry of Health conducts seasonal monitoring of Culex tarsalis populations and West Nile virus-infected mosquitos pools to alert the public about increasing infection risk. Similar monitoring is conducted in other provinces including Manitoba, where the first positive mosquito pool of the season was announced in early July. Although mosquito pools are often the first sign that the virus has arrived in the province, it is not unusual for West Nile virus infections to show up in wild birds first. These cases highlight wild bird disease surveillance as an important tool in the early detection of West Nile virus in Saskatchewan.
