Reduce the risk – Protect yourself

West Nile virus

West Nile virus (WNv) is a mosquito-borne virus that can cause mild symptoms or, in rare cases, a more serious West Nile neurological syndrome. Mosquitoes become infected with WNv when they feed on infected birds. Only three of the 43 species of mosquitoes present in Alberta are likely to carry the virus. WNv is not known to be spread by birds or other animals to people, or by direct person-to-person contact.

The risk of getting WNv in Alberta remains low. Even in other provinces where the virus is present, only a small percentage of mosquitoes will carry the virus, and only a small number of people bitten by an infected mosquito will develop serious illness.

Personal protection

The best way to reduce the risk of infection is to avoid mosquito bites. Severe disease is rare, but can happen at any age. The risk of serious illness increases with age. Everyone can take some simple precautions to reduce their own risk.

• Use a mosquito repellent containing DEET or other approved ingredients on exposed skin; apply it to clothing as well, because mosquitoes can bite through fabric.
• Wear long-sleeved shirts and pants during peak mosquito times.
• Place mosquito netting over infant carriers when outdoors.

Around the yard

Make sure there is no standing water in your yard where mosquitoes can lay their eggs.

• Look for any place where water can collect. This can be a bird-bath, unattended pet watering bowl, inflatable wading pool, fish-pond, old tire, plastic tarp or bucket. Do not let water stand in these places for more than seven days. Note: Chlorinated swimming pools are an exception.
• Clean leaves and debris from eavestroughs regularly to prevent clogs that can trap water.
• Use a mesh-screened lid to keep mosquitoes off the water surface of rain barrels. Wrap screening tightly around any open joints on the downspouts.

• Avoid excessive lawn watering. Save water – and keep mosquitoes down!

Around the house

Keep mosquitoes out of the house by following these simple steps:

• Check all window and door screens; repair any holes.
• Keep outside doors closed. Consider installing an automatic door closer if your family forgets to shut the door.
• Use mosquito netting or screened enclosures to let your family enjoy protected outdoor living during periods of high mosquito activity.

The symptoms

Most people who become infected with West Nile virus will experience no symptoms, or a mild fever.

• Very few individuals will experience the more severe symptoms of West Nile neurological syndrome.
• The Provincial Laboratory of Public Health will provide results on tests of human samples within one week.

West Nile fever

West Nile fever is a mild illness. Symptoms occur three to 15 days following the bite of an infected mosquito, and can include:

• Fever;
• Headache;
• Body aches;
• Skin rash; and
• Swollen glands.

West Nile neurological syndrome

In some individuals, particularly the elderly, WNv can cause serious disease that affects the brain, either in the form of encephalitis or meningitis. This syndrome can cause permanent neurological damage, and can be fatal. Symptoms related to the syndrome include:

• High fever;
• Coma and tremors;
• Headache and neck stiffness;
• Stupor and disorientation;
• Sudden muscle weakness; and
• Paralysis;

The risk of getting WN neurological syndrome is limited to persons in areas where the virus is present, and is higher in persons 50 years of age or older, or in those with weakened immune systems.

Illnesses related to mosquito bites are rare, but you should see a doctor immediately if you develop these symptoms.

While there is no specific treatment for West Nile neurological syndrome, doctors will treat individual symptoms as they occur.

Animals and WNv

Domestic animals

Dogs, cats, cattle and other animals are not affected by West Nile virus. Horses, donkeys, mules and domestic geese are the only livestock that can be seriously affected.

West Nile virus and birds

Although many bird species can be infected with the WNv, mortality is rare except in members of the Corvid family (crows, magpies, ravens, blue jays and grey jays). Because of these fatal infections and because crows are widespread throughout the province, the Alberta WNv surveillance program of wild birds is focused on fresh dead crows.

What should I do if I find a dead crow?

When moving any “found dead” wildlife, always wear gloves, pick up the carcass using a bag inverted over your hand, or use a stick to move the dead animal into a container. Do not handle dead wildlife directly with your hands.

West Nile virus and horses

Mammals in general are very resistant to infection with WNv. Although individual mammals may be bitten by infected mosquitoes, they generally produce an immune response that prevents infection. Horses are an exception – they are particularly susceptible to WNv.

Testing horses

Detection of exposure to WNv in most horses is restricted to a blood test that identifies antibodies to WNv. Routine testing of horses is not recommended, even if the virus has been confirmed in the area. Specialized laboratory tests can confirm the presence of WNv in the brain or spinal cords of horses dying or being euthanized and are available to your veterinarian.

Treatment for horses

There is no specific therapy for WNv infection. Veterinarians use supportive therapy such as intravenous fluids and provide care to prevent secondary infections. A vaccine for horses is now available through veterinarians.

There is no scientific evidence to indicate that WNv can be transmitted directly from horses to other species, including humans; therefore quarantine of affected horses is not necessary.

Mosquitoes

Mosquito surveillance program

The province, in conjunction with municipalities, conducted mosquito surveillance programs from 2003–2008 to learn more about the province’s mosquito population and to detect the virus.

Mosquito control products

Insecticide spraying of adult mosquitoes is not considered to be the best form of control. Mosquitoes can easily hide and avoid contact with an insecticide being applied as a fog or spray. All insecticides that control adult mosquitoes kill many other “good” insects as well.