August 03, 2006
Initial test results indicate five human cases of West Nile virus in Manitoba.
Further testing and investigation is underway to confirm these as cases of West Nile virus, when and where exposure may have occurred and the severity of illness. One positive test result was identified by Canadian Blood Services from a blood donor. Four positive test results were identified by Cadham Provincial Laboratory.
Information on these cases, including decade of age, gender, regional health authority of residence, likeliest area of exposure and classification of disease, will be provided on the website when it becomes available.
In 2005, 58 cases of West Nile virus were identified in Manitoba. Of those, 10 cases were identified as West Nile virus neurological syndrome (the most severe form of the disease), 45 cases were identified as the less-severe West Nile virus non-neurological syndrome and three cases showed no symptoms. The first human cases last year were reported on Aug. 4.
In previous years, the last week of July and the first three weeks of August have been the peak period for the risk of human exposure to West Nile virus in Manitoba. Even though mosquito activity may appear to be low, this is the most important time to take personal protective precautions against mosquitoes in both urban and rural areas.
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.
Adult mosquito trap information from the week of July 23 indicates the numbers of Culex tarsalis mosquitoes in southern Manitoba increased compared to the numbers from the week of July 16.
Preliminary trap information from the week of July 30 indicates the Culex tarsalis numbers in many southern Manitoba communities are continuing to increase compared to the numbers from the week of July 23.
During hot weather, mosquitoes are less likely to be active during the day and more likely to be active at dusk. This is particularly true for Culex tarsalis, which are often less noticeable than nuisance mosquitoes. Heat is one factor that affects the development of Culex tarsalis mosquitoes and Culex tarsalis activity increases when the average daily temperature is above 16 C.
Mosquito samples from four additional communities across southern Manitoba from the week of July 23 were identified as positive for West Nile virus. These communities are Brandon, Deloraine, East St. Paul and Stony Mountain.
This year, positive mosquito samples have been found in 17 Manitoba communities: Steinbach, Carman, Selkirk, Boissevain, Carberry, Portage la Prairie, Gimli, Niverville, St. Andrews, Beausejour, Headingley, West St. Paul, Winnipeg, Brandon, Deloraine, East St. Paul and Stony Mountain.
At this time, the only community where an order for adult mosquito control has been issued is for a targeted area of the Rural Municipality of West St. Paul. Two nights of spraying have been completed. Further spraying will depend on the results of ongoing mosquito surveillance.
Information on adult mosquito control for West Nile virus, including spraying schedules, is available on the Manitoba Health website at http://www.gov.mb.ca/health/wnv.
Manitobans can reduce the number of Culex tarsalis mosquitoes around their homes 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.
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.
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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