West Nile Virus

The spread of West Nile Virus in Ontario has attracted the attention of public health officials, the media and Ontario residents. At this time, the human health risk of West Nile Virus remains minimal compared to other human health risks. However, knowledge of the scope and severity of illness is growing as this newly emerging virus extends across North America.

West Nile Virus is a public health issue. The Ontario Ministry of Health and Long-Term Care, in association with local health units across the province, has the primary responsibility for research and public education about West Nile Virus. As with other public health issues, these agencies have requested the assistance of the people of Ontario and other institutions, such as Conservation Authorities, to help deal with the virus.

The Upper Thames River Conservation Authority (UTRCA) has adopted a strategy to help protect its staff and members of the public who use UTRCA facilities. The components of the strategy are public education, monitoring and surveillance, and removal of stagnant water sources.

Public education - UTRCA is providing information in response to the public perception of risk due to the virus near wetlands, flood plains, natural areas and storm water management ponds. The UTRCA will continue to communicate to our visitors and private landowners adjacent to our natural areas about the importance of eliminating stagnant water areas where the carrier species breed and about preventative measures for mosquito bites.

Monitoring and surveillance - UTRCA will report dead crows to local health units to help them track the spread of West Nile Virus, as well as identify and map potential mosquito breeding areas within our Conservation Areas.

The UTRCA is part of a provincial effort to monitor methoprene concentrations in streams. Methoprene is a larvicide that will be applied this year to control mosquito populations and the West Nile Virus. There are 28 monitoring sites from Ottawa to Windsor. The UTRCA is monitoring at three sites: the Thames River at Komoka, the Avon River and Dingman Creek.

Removal of stagnant water sources - UTRCA will inspect our properties and remove sources of stagnant, polluted water such as aluminum cans, blocked eaves and road ruts and small ponding areas that are potential breeding locations for the mosquitoes that carry West Nile Virus.

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What is West Nile Virus?

Human Illness from West Nile Virus

Human illness from the West Nile Virus is still rare, even in areas where the virus has been reported. According to the Centers for Disease Control (CDC), the chance that any one person will become seriously ill from an infected mosquito bite is low. Many people who have contracted WNV do not even know it. About 20% of those infected will have a mild illness with flu-like symptoms (mild fever, headache, muscle aches, stiff neck, swollen glands, skin rash) within 3 to 15 days following the bite of an infected mosquito. Less than 1% of those infected will develop encephalitis (swelling of the brain) and may experience prolonged muscle and neurological problems. Personal preventative measures are the most effective way of protecting yourself against WNV. Once you have WNV and recover, you are immune for life.

How is the virus spread?

West Nile Virus is usually carried by birds and spread when a mosquito feeds on an infected bird and then bites other birds, animals or people. The virus is carried in the mosquito’s salivary glands. During blood feeding, the virus may be injected into the animal or human, where it may multiply, possibly causing illness. The virus as a single dose is not powerful; several mosquitoes infected with the virus must bite before the virus will infect a human.

According to the CDC, very few mosquitoes are infected with the virus, even in areas where the virus is circulating. There are approximately 50 species of mosquitoes in Southern Ontario. Approximately 18 species can carry the virus but not all mosquito species are capable of transmitting it. At present, the mosquito species of most concern in the transmission of the West Nile virus to humans are the Culex species or catch basin mosquito. They are active from May to August. They prefer highly polluted and stagnant waters for breeding (i.e. water in ditches, eavestroughs, bird baths and roadside catch basins) and are more common in urban rather than rural areas. These species tend to be more active between dusk and dawn. The other species of concern are the Aedes species. These species prefer temporary wet areas such as flood plains for breeding and feed throughout the day or night. Both species are relatively weak fliers, highlighting the importance of eliminating mosquito habitat in backyards as the primary method for reducing mosquito populations.

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Take Action - Protect Yourself!

Monitor the Spread of West Nile Virus

Crows, blue jays and ravens usually die as a result of having contracted West Nile Virus.  Report all sightings of dead crows and any large numbers (i.e five or more) of bird deaths to your local health unit.

Personal Protection

Mosquitoes prefer dark places rather than direct sun, so dawn, dusk and early evening are peak mosquito-biting times:

• Limit your outdoor activity during dawn and dusk.
• Wear long sleeved, light coloured clothing and long pants.
• Use insect repellent containing DEET on skin or clothes.

• An effective repellent will contain 20-30% DEET. Avoid using products containing more then 30% DEET as it may cause side effects, particularly in children, and provides no additional protection.

• Note: Read and follow the directions on the product. In general, use the lowest effective concentration of DEET that is appropriate, do not apply to open wounds or scratches, eyes or mouth, avoid prolonged and excessive use of DEET and wash all treated skin after returning indoors. Repellents should not be applied to children under 3 years old.

Reduce the Spread of West Nile Virus

Mosquitoes prefer stagnant, nutrient rich water and temporary wet areas for breeding:

• Empty all standing water from small containers at least once a week (e.g. flower pots, buckets, plastic containers, bird baths, discarded tires, etc.).
• Clear eavestroughs and downspouts.
• Add an aerator to fish ponds.
• Screen windows and doors.
• Store wheelbarrows, etc. upside down.
• Clear out dense shrubbery where mosquitoes breed and rest.
• Fill in small low spots on your property so water cannot collect.
• Refer to the Health Unit pamphlet for other tips.

Note: Vitamin B, vegetable oil and ultrasonic bug -zapping devices are NOT effective in preventing mosquito bites or reducing mosquito populations. In fact, they may harm the environment or discourage the presence of natural mosquito predators.

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