West Nile Virus Update - April 2010 (pdf file)

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FAQs

1. What is West Nile virus (WNv)?
2. What are the symptoms of WNv?
3. Is there a vaccine?
4. Who is at risk?
5. How is the virus spread?
6. How can I protect my family and myself against West Nile Virus?
7. What is the likelihood of contracting West Nile virus?
8. Is there a test for West Nile virus?
9. Where and what type of laboratory tests are available for West Nile virus?
10. Can we still have our birdbaths full of water, as long as the water is changed every other day?
11. Assuming that household pets are at risk of contracting West Nile Virus as well - how are we to protect them? Has anyone spoken to veterinarians on signs of illness of a family pet and what to do if they appear to have symptoms?
12. What is the York Region West Nile Virus control plan for 2003?
13. What is larviciding?
14. If larvicides and pesticides are being sprayed to kill off some of the mosquitoes, wouldn’t that be bad for the environment?
15. Are permits required to carry out larviciding?
16. It would be useful to know what can be done to prevent ornamental ponds becoming mosquito- breeding areas. I know fish are a solution, but what can we add to the water when there are no fish, without killing the plants?
17. We have a small garden fountain that recirculates water and has to be topped up regularly. We do not run it all the time. Is there a commercially available larvicide we could add to the water from time to time?
18. I have a rain barrel with a screen on the top it, would it still be a breeding area for mosquitoes? I have heard of putting bleach or dish soap in the water but wouldn’t that be harmful if you want to recycle the water for your plants?
19. I have read that purple martins and bats can help reduce the mosquito population. Is this a good way to prevent West Nile?
20. I bought a bug zapper and installed it in my backyard. Will that help protect me from West Nile virus?
21. I read that crows are the main bird carrying West Nile Virus. Are ravens also carriers?
22. Why are dead birds being collected?
23. If we find a dead bird, what are we supposed to do? Should we phone a hotline or just dispose of the dead bird?
24. What is York Region Health Services Health Connection?

1. What is West Nile virus (WNv)?

West Nile virus is an illness that is contracted by mosquitoes when they bite infected birds. The virus can spread from infected mosquitoes to humans, birds and other mammals like horses.

2. What are the symptoms of WNv?

Symptoms of WNv may range from mild illness such as “West Nile Fever”, to serious neurological illness such as encephalitis (inflammation of the brain). Research shows that four out of five people who are bitten by an infected mosquito do not show any symptoms of the virus at all. Other common symptoms include:

• Fever
• Muscle weakness
• Stiff neck
• Confusion
• Severe headache
• Sensitivity to light
• Extreme swelling or infection at the site of the mosquito bite

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3. Is there a vaccine?

Researchers are working hard to develop a vaccine to protect humans from West Nile virus, but at this time no vaccine is available. Interestingly, studies indicate that some people in West Nile virus-infected areas were found to have produced antibodies against the virus, as a source of protection against future infection.

4. Who is at risk?

Everyone who is active or outside during the summer months is at risk of encountering West Nile virus. Those with weaker immune systems, including those over 40 years of age and individuals who suffer from chronic diseases may be at greater risk for serious health implications.

5. How is the virus spread?

West Nile virus is spread from infected mosquitoes to humans. It is not however spread through direct contact from one person to another. International research has linked transmission of West Nile virus through blood transfusion, and further study is being done to confirm if the virus can be passed from a mother to her unborn child and through breast milk.

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6. How can I protect my family and myself against West Nile Virus?

Protect yourself and your family by following these simple steps:

• Cover up. Mosquitoes are attracted to darker, more intense colours so wear light-colour clothing when going outside when mosquitoes are active. It is recommended that you wear long sleeved shirts or jackets, long pants and tuck pants into socks for extra protection
• Use insect repellent. Consider using an insect repellent containing DEET. The concentration of DEET should be no greater than 30% for adults and no greater than 10% for children. Follow the instructions on the label carefully
  1. Apply repellent sparingly on exposed skin and clothing. Do not use under clothing
  2. Do not use repellent on open wounds or irritated or sunburned skin
  3. Do not get repellent in eyes. If this happens, rinse with water right away
  4. Wash skin with soap and water when you return indoors or when protection is no longer needed
  5. Avoid breathing mist from spray-type repellent. Always apply in a well-ventilated area. Never apply spray repellent inside a tent. Do not use near food
  6. Do check for sensitivity, apply repellent to a small area of skin on the arm and wait for 24 hours before use
• Clean up around the house. The best way to keep mosquitoes away is to clean up areas of standing water where they like to breed. Look around your house and property and get rid of places that are mosquito-friendly, including:

  1. Containers of standing water. Clean up and empty containers where water collects, such as in old tires, flower pots, wheelbarrows, barrels or tin cans that are outdoors. Change water in bird baths every other day and if appropriate, drill holes in the bottoms of containers so water can't collect.

  2. Check swimming or wading pools. Immediately remove water that collects on pool covers, make sure the pool pump is circulating and turn over wading pools when not in use.

  3. Check and clear eaves and drains. Clear leaves and twigs from eavestroughs, storm and roof gutters throughout the summer, make sure drainage ditches are not clogged and check flat roofs frequently for standing water.

  4. Regular home and lawn maintenance. Decaying debris can end up in storm sewers as a food source for mosquito larvae. Turn over compost frequently and fill in low depressions in lawn areas, clear out dense shrubbery where mosquitoes like to rest and make sure door and window screens are tight fitting and in good repair. Spread the word. Point out potential breeding areas to your neighbours.

  5. Flush rear yard catch basins with clean water every 4 days. If there is no substantial rainfall during May to October for a period of 4 consecutive days, using a garden hose flush the catch basin with an ample amount of water to clear the area of standing and stagnant water

  Another option is to place over the catch basin plastic screening (used for patio doors) that has been stretched over a 2-inch by 4-inch lumber frame formed into a small pyramid shape.

  Carefully lift the catch basin lid and place the screen over the opening then lower the lid gently over the screen to hold it firmly in place. The screen cover should be removed during periods of heavy rain. To prevent flooding, guard against debris becoming lodged against the screen, if materials do collect around the screen during a rainstorm, poke holes into the mesh to let the water flow unimpeded into the catch basin. The screen can easily be replaced.
  If you are away from your home for several days, a neighbour should be responsible for monitoring the catch basin.

  Please not that it is illegal to place toxic chemicals into any catch basin or water source. A Ministry of the Environment Permit is required before any larvicide can be used in water that does not directly remain on the owner’s property.
  

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7. What is the likelihood of contracting West Nile virus?

In Ontario, the most common mosquito species that carries West Nile virus is the Culex pipien (also known as the rain barrel mosquito), and tends to concentrate more in urban areas. Overall, most doctors believe that the risk of people becoming seriously ill with West Nile is extremely low.

8. Is there a test for West Nile virus?

Canadian Blood Services expects to have a new test in place by July 2003 that will screen for West Nile virus for blood donors. Canadian Blood Services advises people not to donate if you are feeling unwell. If you have donated blood and begin to feel sick after your donation, you are requested to immediately contact Canadian Blood Services at 1-888-2-DONATE (1-888-236-6283).

9. Where and what type of laboratory tests are available for West Nile virus?

All West Nile virus testing takes place in Ontario with a turnaround time of three days. If you are being tested for WNv, you should contact and notify your physician.

10. Can we still have our birdbaths full of water, as long as the water is changed every other day?

As far as bird baths being breeding grounds for mosquitoes, one simply has to do the math. Mosquitoes lay their eggs in standing water, and the larvae need two to three days to hatch. So, if you replace the water in your bird bath every two days during their breeding season no mosquitoes will have the opportunity to reproduce. The National Bird Feeding Society recommends changing the water every other day regardless of West Nile virus, since bacteria that can harm birds grows in dirty water.

11. Assuming that household pets are at risk of contracting West Nile Virus as well - how are we to protect them? Has anyone spoken to veterinarians on signs of illness of a family pet and what to do if they appear to have symptoms?

Any mammal or bird can be exposed to West Nile virus if bitten by an infected mosquito. Horses and birds appear to be particularly susceptible. Although dogs and cats can become infected with the virus, they do not appear to develop signs of the disease except under rare circumstances. Still, you might want to consider keeping your household pets indoors during dusk and dawn when mosquitoes are most prevalent. Also be sure not to leave pet bowls lying around outside where water might become stagnant. Do NOT spray your pets with products containing DEET. There are safe insect repellents available for pets. Ask your veterinarian and be sure to follow the label directions.

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12. What is the York Region West Nile Virus control plan for 2003?

The York Region WNv control plan for 2003 includes:

• Extensive public education regarding effective measures to prevent exposure to WNv, including brochures, posters, transit advertising, public information sessions and community outreach activities
• Mosquito, bird and human surveillance
• WNv control activities, including a larviciding strategy in three phases
  • May: The first application will target the catch basins in the identified WNv "hot spot" areas where positive human, bird and mosquito cases were identified in 2002
  • June and July: The second and third applications will target all catch basins in Richmond Hill, Vaughan, Markham, Newmarket, Aurora, Keswick, Holland Landing and other urban areas with catch basins, including the "hot spots"
• In addition, newly identified positive bird, mosquito and human cases in 2003 will be mapped and larvicide applied in the catch basins around those newly detected positives
• Residents in the targeted areas will be notified 48 hours prior to larviciding activities.
  

13. What is larviciding?

Larviciding is a safe and effective measure for the control of West Nile virus. Methoprene is the larvicide that will be used. It comes in slow-release pellet-like formulations, not sprayed, and is administered when the mosquito is in the larval stage of development.

Methoprene is a synthetic growth hormone that interferes with the mosquito life cycle, preventing the mosquito larva from reaching maturity and reproduction. It has been approved by both the provincial and federal governments and is considered safe for humans and the environment.

In some instances a larvicide called BTi (Bacillus thuringiensis israelensis) may be used in storm water management areas. This is a bacterium that disrupts mosquito larvae digestion and kills them. The larvicide has little effect on other insect species, has been approved by the federal government and is considered safe for use.

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14. If larvicides and pesticides are being sprayed to kill off some of the mosquitoes, wouldn’t that be bad for the environment?

In Canada, all pesticides are registered by Health Canada's Pest Management Regulatory Agency (PMRA). Once this agency has made a decision to register a pesticide product in Canada, the Ontario Ministry of Environment (MOE) is responsible for regulating its sale and use through training, licensing and permit regulations.

Any questions regarding West Nile virus and pesticides should be addressed to the MOE public inquiry line toll free at 1-800-565-4923.

15. Are permits required to carry out larviciding?

Permits are required to apply larvicides on public and private property. The Ministry of the Environment issues the permits to individuals and contractors who are licensed to use these products. York Region possesses a permit; the City of Vaughan does not.

Conditions are attached to the permit, including the requirement that residents in the targeted areas are notified before treatment commences.

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16. It would be useful to know what can be done to prevent ornamental ponds becoming mosquito- breeding areas. I know fish are a solution, but what can we add to the water when there are no fish, without killing the plants?

Mosquitoes breed in standing water. Aerate ornamental ponds. Fountains, drippers, misters and pumps keep the water surface disturbed, thereby eliminating the possibility for mosquitoes to reproduce. Recirculating water features decrease the chances of mosquito egg-laying, but even moving water may have still corners, so fish can help out in those situations.

17. We have a small garden fountain that recirculates water and has to be topped up regularly. We do not run it all the time. Is there a commercially available larvicide we could add to the water from time to time?

There are commercially available larvicides that are laced with a type of bacteria common in soil known as BTi — Bacillus thuringensis israelensis. The bacterium disrupts the larva’s digestion and kills them. This comes in a pellet formulation. Placed in the water (the amount depends upon the volume of water), the organisms go to work on the larvae.

Remember to put in fresh BTi every 4 days or as directed on the package. These products are effective, economical and do no harm to fish or desirable insects and other aquatic species. They are generally available in most garden centers and other stores.

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18. I have a rain barrel with a screen on the top it, would it still be a breeding area for mosquitoes? I have heard of putting bleach or dish soap in the water but wouldn’t that be harmful if you want to recycle the water for your plants?

Rain barrels have become popular with homeowners and gardeners who want to conserve water. An average sized roof will supply some 4000 litres of water from April to August! But, mosquitoes will breed in the rain barrel if you do not install a fine mesh screen over the opening.

The screen has to be similar to those on your windows, in other words, sufficient to stop mosquitoes from entering. If you have a rain barrel with a screen, you should check to ensure it is in good repair. If your rain barrel is screened properly, there is no need to add anything to the water, as the mosquitoes will be unable to enter the barrel and breed. Otherwise you should drain your rain barrel and install a screen before using it. In addition, barrels should be anchored securely to the ground to help prevent curious children and pets from accidentally falling into or tipping over the barrel.

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19. I have read that purple martins and bats can help reduce the mosquito population. Is this a good way to prevent West Nile?

Bats and purple martins are indiscriminate feeders and eat a wide variety of insects, including mosquitoes. However, contrary to popular opinion, they don't eat enough to be relied upon for mosquito control. They would have to work their way through an astronomical number to make any kind of dent in the adult population.

20. I bought a bug zapper and installed it in my backyard. Will that help protect me from West Nile virus?

Bug zappers kill many kinds of insects, including moths and beetles. Mosquitoes make up a very small percentage of the insects that are killed by bug zappers. Bug zappers do more harm than good by killing other insects that are natural predators of mosquitoes. They attract more mosquitoes to an area and end up killing thousands of beneficial insects that do not harm humans.

21. I read that crows are the main bird carrying West Nile Virus. Are ravens also carriers?

Yes, Crows and other corvids (magpies, jays, grackles, ravens, blackbirds) appear to be particularly vulnerable to West Nile virus. In fact, most bird species can carry the disease, but it seems corvids are most susceptible to the virus.

Dead crows were the first indicator of WNV in 66% of U.S. counties; blue jays and other corvids (magpies, jays, ravens, etc) appear to be the most important indicator species for WNV in North America.

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22. Why are dead birds being collected?

Like humans, West Nile virus is transmitted to the bird population by infected mosquitoes. Symptoms in birds manifest as neurological signs such as convulsions, tremors, head tilt, wing droop and paralysis. Crows are known to be most susceptible to the disease and act as an early warning system for the presence of the virus in a particular area.

York Region Health Services asks residents to report dead crows, with suitable specimens being collected and submitted to the Canadian Co-operative Wildlife Health Centre in Guelph for screening. All crows that are reported will help to map out possible West Nile virus activity in York Region.

23. If we find a dead bird, what are we supposed to do? Should we phone a hotline or just dispose of the dead bird?

As part of the West Nile virus surveillance program, Health Units in Ontario will record reports of dead crows or ravens found by residents in their communities. If you find a dead bird contact York Region Health Services Health Connections at 1-800-361-5653, Monday through Friday, 8:30 a.m. to 4:30 p.m. or during weekdays between 4:30 p.m. and 8 p.m. and weekends between 8 a.m. to 8 p.m., call 905-830-3375.

When calling to report a dead bird, please provide the following information:

• The exact location of the bird (i.e. street address, postal code, cross streets)
• The condition of the bird (i.e. intact, hurt, fresh, mauled, feathers ruffled)
• Name and phone number of caller
• Species of bird, if known
• Not all birds will be collected for testing, especially after WNV is already known to be in the area, you may be asked to dispose of the dead bird

  When handling dead birds

  • WNV cannot spread directly from birds to humans. However, dead birds should not be handled with bare hands. Always wear gloves. Heavy-duty leak-proof rubber gloves are recommended.
  • Ensure that you and your clothing do not contact the bird or its blood, secretions or feces.
  • Grasp the bird with your hand protected by several layers of leak-proof plastic bags. Turn the bags inside out over the bird so the bird ends up inside the bags.
  • Handle the birds so that neither beak nor claws puncture the bag or gloves.
  • After the bird is safely contained, wash hands thoroughly with soap and water, or use a hand sanitizer.
  • Rotten carcasses should not be submitted for examination.

  Disposing of dead birds not submitted for examination

  To dispose of a dead bird:

  • Bury the carcass approximately two feet deep in a flowerbed or other area where it will not be disturbed. It is not recommended that you use a vegetable garden for this purpose.

  OR

  • Double bag the bird in sealed plastic bags and place in the garbage for pickup. The easiest way to do this is to either place the bird in the bag using a garden trowel then tie off the top or place your gloved hand within the two bags, grab onto the bird, bring the rest of the bag down around the bird, and then tie off the top.

24. What is York Region Health Services Health Connection?

Health Connection provides a confidential line to health information and services with access to a health professional from 8:30 a.m. to 8:00 p.m. Monday to Friday, and 8:30 a.m. to 4:30 p.m. on weekends. Public Health Nurses, Public Health Inspectors, Dental Hygienists and a Registered Dietician, provide confidential counselling, health and community resource information and a referral service to callers.

Automated access to health topic recordings is available seven days per week, twenty-four hours per day. The toll free number is 1-800-361-5653.

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Useful information links

York Region Health Services West Nile Information

Healthy Ontario West Nile Virus Information

The Ontario Ministry of Environment Pesticide Information

Health Canada West Nile Surveillance Information

United States Centres For Disease Control West Nile Information

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