July 27, 2006

An order under Manitoba’s Environment Act has been issued to control adult mosquitoes in the area surrounding City of Winnipeg biosolid storage pads in the Rural Municipality of West St. Paul.  This site has historically attracted large numbers of Culex tarsalis each year.  At this time, a significant number of these mosquitoes have become infected with West Nile virus and are likely to migrate into nearby residential areas.

In addition, mosquito samples from nine additional communities across southern Manitoba from the week of July 16 were identified as positive for West Nile virus.  These communities are Carberry, Portage la Prairie, Gimli, Niverville, St. Andrews, Beausejour, Headingley, West St. Paul and Winnipeg.  In most of these communities, surveillance indicates the number of infected Culex tarsalis mosquitoes is low.

At this time, no other orders have been issued for adult mosquito control in any community other than West St. Paul.  The province continues to monitor adult Culex tarsalis mosquito numbers in these communities and across southern Manitoba.

In previous years, the last week of July and the first few weeks of August have been the peak period for the risk of human exposure to West Nile virus in Manitoba.  Surveillance data indicate the virus is present throughout southern Manitoba at this time.

Adult mosquito control to reduce the risk of West Nile virus will take place in the evening and at night and will begin within the next two days, weather conditions permitting.  The spraying will take place within an approximately three-kilometre area of the City of Winnipeg biosolid storage pads including sections of West St. Paul and the city of Winnipeg.

Information on adult mosquito control schedules for West Nile virus and a description of the area to be sprayed will be available on the Manitoba Health website at http://www.gov.mb.ca/health/wnv.

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

·         making sure doors and window screens fit tightly and are free of holes.

Manitobans can reduce the number of Culex tarsalis mosquitoes around their home by reducing standing water.  This includes:

·         regularly cleaning and emptying eavestroughs, bird baths and other items that might collect water;

·         ensuring rain barrels are covered with mosquito screening or are tightly sealed around the downspout; and

·         making sure yards are clear of old tires or other debris that collect water.

Adult mosquito trap information from the week of July 16 indicates a rise in the number of Culex tarsalis mosquitoes compared to the week of July 9. 

Preliminary trap information from the week of July 23 indicates the Culex tarsalis numbers in many southern Manitoba communities continue to rise.  Heat is major factor that affects the development of Culex tarsalis mosquitoes and Culex tarsalis activity increases when the average daily temperature is above 16°C.

This year, positive mosquito samples have been found in thirteen Manitoba communities:  Steinbach, Carman, Selkirk, Boissevain, Carberry, Portage la Prairie, Gimli, Niverville, St. Andrews, Beausejour, Headingley, West St. Paul and Winnipeg.

The risk of becoming ill from West Nile virus is rising and will increase in the coming weeks.   To date, no human cases of WNV have been identified in Manitoba.

Testing for West Nile virus is ongoing at Cadham Provincial Laboratory.  Weekly average trap counts of Culex tarsalis by regional health authority are available on the province’s West Nile virus website at http://www.gov.mb.ca/health/wnv.

Health Canada has concluded that the use of malathion for adult mosquito control in residential areas using ultra-low-volume application will not pose a health concern.  However, people who wish to reduce their exposure to malathion can take precautions, including:

·         closing all doors and windows,

·         avoiding trucks while spraying is underway,

·         turning off fans and air conditioners or setting them at exhaust,

·         removing clothes and children’s toys from outdoor areas,

·         washing any household items or toys left outside before using them, and

·         washing fruits and vegetables.

For more information, visit http://www.gov.mb.ca/health/wnv or call Health Links at 1‑888‑315‑9257 or 788-8200 in Winnipeg.

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