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Mosquito Mapping

News Release
For immediate release
July 23, 2007 

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Mosquito Mapping Shows West Nile Virus is A Fact of Life

Since 2001, Algoma Public Health has been gathering data to better understand West Nile Virus in our District. Algoma Public Health has been working with the Innovation Centre to map mosquito results. We are hoping to expand the mapping capabilities to include other parts of the Algoma District in the near future.

“As communities, we need to work together to keep the risk as low as possible”, says Kara Flannigan, coordinator for Vector-borne Diseases at the health unit. “The virus is here to stay. As northern-Ontarians, we need to change our beliefs that mosquitoes are only a nuisance because they spread disease now. We have to adapt our behaviours and accept that the risk has changed.”

West Nile virus is a disease that is transmitted to humans by the bite an infected mosquito. Symptoms usually develop between two and 15 days after being bitten. Of those who show symptoms, most will experience mild illness including fever, headache, body ache, nausea, vomiting and rash on their chest, stomach or back. About one in 150 people infected will experience serious symptoms including high fever, severe headache, muscle weakness, stiff neck, confusion, tremors, numbness and sudden sensitivity to light. There is no cure, so prevention is the strategy.

Prevention includes protection from mosquito bites and decreasing mosquitoes around us.

Preventing mosquito bites is easy:
• Use insect repellent containing DEET (30% for adults, 10% or less for children)
• Wear light-coloured long-sleeves and pants or specialized bug-protective clothing
• Avoid being outside during high mosquito activity times, such as dusk and dawn

It’s easier to prevent mosquito bites if there are fewer around to bite people. Because mosquitoes lay eggs in still water, eliminating standing water is crucial to decreasing their numbers. Water collects on public and private property.

Last year, standing water was identified in buried electrical vaults across the City of Sault Ste. Marie. Mosquito larvae were found in the water. To kill the larvae, licensed City employees treated the water by adding environmentally-friendly bacteria. This was done again this year and may become a seasonal activity. Storm drains in the street can also attract mosquitoes. They differ from vaults because a heavy rain will flush out the water and the larvae.

Private property is also a source of mosquitoes. Standing water can collect in many things so it’s important for residents and businesses to inspect their properties weekly and get rid of the water. Check bird baths, old tires, unused containers like barrels, flower pot saucers, swimming pool covers, wading pools, clogged gutters and eaves troughs, clogged drainage ditches, small containers like cans or bottle tops, unused children’s toys or vehicles. For things like bird baths and wading pools, change the water every three days or so.

Because birds and mosquitoes are so important to the spread of the disease, public health units across the province engage in a variety of activities to monitor activity. These include tracking dead bird sightings, checking for larval activity, testing birds and mosquitoes for West Nile Virus, checking mosquito types in our area. Crows and live mosquitoes are submitted for viral testing. The first positive bird was confirmed in 2002. The first positive mosquitoes were caught in 2005.

Mosquitoes are also sent to be identified as to species of mosquito. Kara explains, “The reason we identify the species of mosquito is because the Culex species are known to be able to spread the disease and if we find this species, we may be able to reduce their numbers. Decreasing Culex may interfere with the spread of West Nile virus.”

“The Culex mosquitoes are more common in urban areas because they prefer laying eggs in man-made areas such as standing water in our backyards and storm drains. So, we identify the “city bugs” and compare them with the other types of mosquitoes. Although overall we have more “bush” mosquitoes, you can’t tell which is which when it comes to bite you. But just because you may be in the country, there’s probably something around that will attract the “city bug” to lay its eggs.”

The Mosquito Trapping Results (2006) map shows both the total number of female mosquitoes caught in traps located in various sites within Sault Ste Marie, as well as the proportion of Culex and non-Culex species caught in the traps. The red portion of the circle represents the proportion of Culex species mosquitoes and the green portion represents the non-Culex mosquitoes. Reviewing the map, the size of the circles shows that the total number of mosquitoes caught in the traps varied as did the proportion of Culex species. Although some traps caught more mosquitoes, the proportion of Culex species was in some instances actually lower than other traps that caught fewer mosquitoes. Although the exact reasons for these differences are not clear, the proximity of some traps to more rural areas may be a factor.

Mapping dead bird sightings has also been helpful. In 2005, a cluster of dead crows was reported in an east end neighbourhood. Testing confirmed a positive crow. Mosquito traps were moved to the area and the first positive mosquitoes in the District were caught. Homes and businesses were visited door to door and provided with information about West Nile Virus and prevention. The City mobilized its team and equipment to clean out standing water in the storm drains in the area.

Kara reminds the public that “Culex species were confirmed in most traps so it is important to take precautions against mosquito bites everywhere. The City has larvicided buried vaults across the municipality in an effort to reduce Culex populations. We can all pitch in and do our part to remove standing water and prevent mosquito bites. Also, remember that the risk of West Nile virus outside the Algoma District may be much higher, so take precautions when traveling.”

Please call 759-5286 or your local Environmental Health office of Algoma Public Health to report dead crows, ravens, and bluejays.

Sault Ste. Marie Innovation Centre