Manitoba Health

September 2, 2010

Manitoba Health reports one mosquito sample tested positive for West Nile virus during the week of Aug. 22 to 28, in Morris. So far this year, a total of 20 positive mosquito samples have been found. Based on the current level of infected mosquitoes, adult mosquito control is not being recommended at this time.

The number of adult Culex tarsalis mosquitoes trapped during the week of Aug. 22 decreased compared to the previous week. Preliminary numbers for the week of Aug. 29 show the number of Culex tarsalis in traps continue to decrease.

The risk of human exposure to West Nile virus is decreasing but the potential for exposure is still present in southern Manitoba. The risk is expected to continue to decline in the weeks ahead. As daytime and evening temperatures become cooler, Culex tarsalis mosquitoes may become more active during the day and early evening, with reduced activity overnight when temperatures are cool.

To date, no human cases of West Nile virus have been identified in Manitoba in the 2010 season.

Weekly average trap counts of Culex tarsalis by regional health authority are available here.

Manitobans can reduce the risk of mosquito bites by:

• reducing the amount of time spent outdoors 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.