Manitoba sees first west nile mosquito

The Office of the Chief Medical Officer of Health reports that Manitoba’s mosquito surveillance program has identified the first Culex tarsalis mosquito samples infected with West Nile virus in Manitoba in 2008.

Samples of Culex tarsalis from adult mosquito traps in the towns of Deloraine and Boissevain in the Assiniboine Regional Health Authority tested positive for West Nile virus.  The samples were collected earlier this week. The numbers of infected mosquitoes are relatively low in these communities and no adult mosquito control has been recommended at this time.

It is anticipated that more positive mosquitoes will be identified in additional communities in the next few weeks. In previous years, the peak risk period for human exposure to West Nile virus has been the last two weeks of July to the first two to three weeks of August.

To date, no human cases of West Nile virus have been identified in Manitoba in the 2008 season. The disease has affected livestock in past seasons, particularly horses.

Manitobans can reduce the risk of mosquito bites 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 mosquitoes around their home by reducing standing water.  To prevent the development of Culex tarsalis mosquitoes, homeowners can:

  • clean eavestroughs and regularly empty bird baths and other items that might collect water,
  • ensure rain barrels are covered with mosquito screening or are tightly sealed around the downspout,
  • clear yards of old tires or other items that collect water, and
  • improve landscaping to prevent standing water around the home.

Weekly average trap counts of Culex tarsalis by regional health authority are available on the province’s West Nile virus website at

Information on the risk of West Nile virus will continue to be provided to the public throughout the summer. Manitobans can also check the West Nile virus website regularly for up-to-date data and information.

For more information about West Nile virus, contact Health Links–Info Santé at 788-8200 or 1-888-315-9257 (toll-free) or visit the Manitoba Health website at

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