April 26, 2004
Manitoba’s West Nile Virus (WNV) Corvid Surveillance program will begin May 5, 2004. The public will be asked to report dead birds from the crow family (corvids) to Health Links/Info Santé (788-8200 or 1-888-315-9257), including crows, blue jays, magpies and ravens. If conditions are appropriate, arrangements will be made to pick up the bird.
Dead birds from the crow family provide the first indication of the presence of West Nile virus in an area. Last year, the first positive corvid was detected on June 13.
Once a positive bird has been confirmed in an area, further birds are no longer needed. Therefore, not all dead corvids will be picked up for testing. Health Links/Info Santé will provide information on how to appropriately dispose of a bird if it is not needed for testing.
The 2004 surveillance program includes mapping and sampling for Culex mosquito larvae and corvid, adult mosquito, equine and human surveillance. Sentinel chicken testing has not provided reliable information about the human risk of WNV and has been discontinued.
The program has a cost-shared intervention component that approves larviciding and contingency adulticiding on a 75 per cent provincial and 25 per cent municipal basis.
At this time of year, the risk of being bitten by a mosquito carrying WNV is considered negligible. Depending on weather conditions, Culex tarsalis, the primary mosquito responsible for human infection with WNV, does not usually begin to appear until June.
Some mosquito traps will be set up in mid-May to monitor and evaluate early season mosquitoes. Larval sampling and larviciding for Culex tarsalis larvae and all traps that will monitor adult mosquitoes during the summer will be in place in June. Municipal insect control programs for nuisance mosquitoes usually begin in April and May.
As part of a spring yard cleanup, Manitobans are advised to take the time to reduce mosquito larval habitats around their homes by:
-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 down spout; and
-making sure their yards are clear of old tires or other debris that collect water.
Updated information on the risk of WNV will be provided to the public throughout the summer. The risk of WNV varies from year to year based on several factors which include infected bird populations, mosquito populations, mosquito infection rates, precipitation and temperature.
The greatest risk for being bitten by WNV infected mosquitoes in Manitoba is during July, August and September.
Most people bitten by an infected mosquito do not become ill. For those who do, the symptoms are usually mild. However, for some individuals, West Nile virus may cause serious illness and in some cases death.
To reduce the risk of WNV infection, Manitobans are advised to wear protective clothing, use a repellent containing DEET (according to label instructions) and reduce the amount of time spent outdoors between dusk and dawn when mosquitoes are most active.
Human cases were detected in southern Manitoba for the first time in the summer of 2003. There were 142 cases: 35 cases of West Nile virus neurologic syndrome, including two deaths, 104 cases of West Nile virus fever and three asymptomatic individuals.
Surveillance for human cases continues year-round. The risk for human illness is anticipated to increase in July.
WNV pamphlets will be available in the next few weeks at local public health offices. For more information about WNV, contact Health Links/Info Santé at 788-8200 in Winnipeg or toll-free at 1-888-315-9257. Please also see the Manitoba Health website at http://www.gov.mb.ca/health/wnv.
WNV updates and bulletins will be issued as necessary and media are advised to check the WNV website for weekly information updates. WNV program staff will be available for media questions.
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