July 12, 2012

WEST NILE VIRUS UPDATE #1

Manitoba Health reports that its mosquito surveillance program has identified this season’s first Culex tarsalis mosquito samples infected with West Nile virus.  At this time, no human cases of West Nile virus have been identified in Manitoba in the 2012 season.
The infected mosquitoes were collected during the week of July 1 from adult mosquito traps in Portage la Prairie and the Sandy Bay First Nation.  Based on the most recent information, the numbers of infected mosquitoes are predicted to be low for this area.  The current estimated risk does not warrant an order for adult mosquito control at this time.
The numbers of Culex tarsalis mosquitoes trapped during the week of July 1 increased throughout southern Manitoba.  The mosquito numbers are highest in central and southwest Manitoba at this time but the potential for human exposure to infected mosquitoes is present throughout southern Manitoba.  Mosquito samples that are positive for West Nile virus may be identified in additional communities in the next few weeks.
Preliminary trap information for the week of July 8 indicates the numbers of Culex tarsalis mosquitoes have increased slightly from the previous week.  The risk of exposure to West Nile virus is expected to increase in the coming weeks, particularly with the current hot, humid weather, which is ideal for Culex tarsalis development and activity.
Taking measures to prevent mosquito bites and reducing standing water around the home can help reduce the risk of West Nile virus exposure.  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 homes 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.

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, 58 communities are participating in the program.
Information on the risk of West Nile virus 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.
For more information about West Nile virus, contact Health Links–Info Santé at 204-788-8200 or toll-free at 1-888-315-9257.  Weekly average trap counts of Culex tarsalis by regional health authority are available on the province’s West Nile virus website at www.gov.mb.ca/health/wnv/.