July 24, 2015
West Nile Virus Update #1
Manitoba Health, Healthy Living and Seniors reports that its mosquito surveillance program has identified this season’s first Culex tarsalis mosquito sample infected with West Nile virus (WNV). At this time, no human cases of West Nile virus have been identified in Manitoba.
The infected mosquitoes were collected during the week of July 12 from an adult mosquito trap in Portage la Prairie. There are currently no orders for adult mosquito control in Portage la Prairie or elsewhere in the province.
To date most of the mosquitoes collected in adult mosquito traps continue to be nuisance mosquitoes which do not transmit WNV. However, the number of Culex tarsalis mosquitoes trapped during the week of July 12 has increased in several communities across southern Manitoba. In addition, preliminary trap information for the week of July 19 indicates that Culex tarsalis numbers continue to increase in a number of communities, most notably in the southern portion of the Prairie Mountain Health Region. Culex tarsalis numbers are lower in comparison to this time last year and 2007 when Manitoba had multiple human cases.
The potential for human exposure to infected Culex tarsalis mosquitoes is present throughout southern Manitoba. The risk of exposure to WNV is expected to increase in the coming weeks, particularly if warm nighttime temperatures persist, as these are ideal conditions for Culex tarsalis development and activity. Manitobans are cautioned the province is entering what has historically been the highest risk period for WNV transmission.
Manitobans can reduce the risk of mosquito bites and exposure to West Nile virus by:
- reducing the amount of time spent outdoors during peak mosquito hours between dusk and dawn;
- using appropriate mosquito repellent;
- wearing light-coloured, loose-fitting clothing; and
- maintaining door and window screens so they fit tightly and are free of holes.
Manitobans can reduce the number of mosquitoes around their homes by eliminating standing water. To prevent the development of Culex tarsalis mosquitoes, homeowners can:
- clean eavestroughs and regularly empty bird baths, old tires and other items that collect water;
- ensure rain barrels are covered with mosquito screening or are tightly sealed around the downspout; and
- improve landscaping to prevent standing water around the home.
The province offers a cost-shared larviciding program for municipalities and communities to take steps to help control Culex tarsalis mosquitoes. To date this year, 52 communities are participating in the program.
Information on the risk of WNV will continue to be provided to the public throughout the summer in a media campaign and at various fairs and festivals. Manitobans can also check the West Nile virus website regularly for up-to-date data and information.
More information about West Nile virus, including weekly average trap counts of Culex tarsalis mosquitoes, fact sheets, posters and information for municipalities and health-care providers, is available at www.gov.mb.ca/health/wnv.
Manitobans can also contact Health Links–Info Santé at 204-788-8200 in Winnipeg or at (toll-free) 1-888-315-9257 for more information.
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