What Hunters Need to Know about the West Nile Virus

What is the West Nile Virus?
The West Nile Virus is a member of the Japanese encephalitis complex, and was first isolated in 1937 in Africa and the Middle East. WN Virus is closely related to St. Louis encephalitis, a naturally occurring virus in the U.S. and Canada. Symptoms of WN virus include: increased body temperature, shaking of tilted head, and imprecise motor skills. The virus is passed when a mosquito bites an infected bird, and then becomes infected. Scientists do not believe that humans can contract the virus from direct contact with an infected human, dog, or other vertebrate.

   With  hunting season just around the corner, hunters want to know about the risk of contracting West Nile (WN) Virus from either handling or consuming wild game birds.

All currently available information indicates that West Nile virus is primarily spread through mosquitoes. There are no reported cases of West Nile virus being contracted through the handling or consumption of wild birds, however West Nile virus is new in North America and there is still much to be learned about the disease.

Over one hundred species of birds have been found to carry the virus, with members of the Corvidae family (crows, blue jays, ravens) showing the greatest mortality from the virus. To date, specimens of the following game birds have been reported positive for WN virus: sandhill cranes, mourning doves, mallards, wood ducks, Canada geese, ruffed grouse, wild turkeys, and ring-necked pheasants.

However, based on studies conducted since the virus first appeared in North America, scientists believe wild waterfowl may be immune to the WN virus. While mallards, wood ducks, and Canada geese have tested positive for the virus, the infected birds were all domestic waterfowl living on park ponds, zoos, and in urban settings.

Furthermore, thousands of birds die each year from avian botulism, many of which are randomly tested for botulism and WN virus. To date, none of these wild waterfowl have tested positive for WN virus.


How It's Spread

When a mosquito bites a bird that's been infected with the virus, the mosquito becomes infected, and can transmit the virus to humans, horses, dogs, or other birds that it bites thereafter.


Image courtesy of the Center for Disease Control and Prevention. Photographer: William Brogdon

Of the forty species of mosquitoes that transmit the virus, three species - Culex pipiens, C. Restauns, and C. salinarious have been implicated as the most common vectors. Larvae of these species are most often found in artificial containers such as bird baths, tin cans, old tires, plastic bottles, rain gutters, etc. These mosquitoes are rarely found in healthy wetlands such as the ones used by North America's waterfowl. In healthy wetlands water fluctuates regularly, which deters these three virus-carrying mosquito species. In fact, mosquito populations are generally reduced in healthy wetlands, versus partially drained and impacted wetlands.


Be Prudent, but not Paranoid

Despite increased media attention, there is no cause for panic about West Nile Virus - but neither is there room for denial. Hunters should follow the usual precautions when handling wild animals, and if you expect to encounter mosquitoes in the field, wear long pants, long-sleeves, and mosquito repellant. Here are a few more recommended precautions that should minimize any possible risk:


  •  Do not harvest or handle sick game birds
  •  When cleaning game or handling live or dead birds, use gloves in order to prevent blood to blood contact
  •  Cook game birds until well done
  •  Soak any utensils used to prepare game birds in a solution of one part household bleach and 10 parts water for 20 minutes
  •  Most importantly, hunters should avoid mosquitoes as they are the most likely means of acquiring West Nile virus. Hunters participating in early teal season hunts should apply insect repellant to clothing and skin.
  •  At home, look for stagnant water in bird baths, plant trays, old tires, wheelbarrows, and other containers around your yard. If you find standing water, pour it out, and be diligent about re-checking these areas at least once a week.

    Image courtesy of the Center for Disease Control and Prevention. Photographer: William Brogdon

    Dogs and the West Nile Virus

    Cases of WNV have been reported in dogs in the U.S., but most infections did not cause severe illness in infected dogs. However, veterinarians in Illinois recently confirmed the first documented canine death from West Nile Virus in North America. An 8-year-old Irish setter/Golden Retriever mix, a wolf and three gray squirrels in Illinois died of West Nile infection. Officials do not expect an epidemic of the virus in household pets, but caution that older dogs, puppies, and dogs that already have weak immune systems could be at risk.

    The infected dog in Illinois showed neurological symptoms, including unusual head bobbing, lethargy, and progressive weakening. The virus appears to have been transmitted by mosquitoes, and researchers stress that people and other pets have a low risk of contracting the virus from an infected dog.

    Dog owners should minimize their pet's exposure to mosquitoes by using screened kennels, and/or repellents approved for use on animals. Do NOT use DEET on dogs. Owners should also limit early morning and late afternoon walks or training sessions, as this time of day leaves people and animals most susceptible to mosquito bites.

    Should your pet contract the virus, don't panic. Officials say there is NO reason to destroy an animal because it has been infected with WNV. Full recovery is likely, and direct transmission of the virus to you or other animal is unlikely. Researchers are currently developing WNV vaccines for domestic animals.



    For more information about the risks of contracting West Nile Virus in specific geographical regions, contact your local department of wildlife and natural resources, state epidemiologist at the state health department, or the U.S. Geological Survey (USGS) National Wildlife Health Center, Madison, WI, at (608) 270-2400.