West Nile Virus (WNV) and Poultry

By Anne Lichtenwalner, DVM, Ph.D., University of Maine Extension

Question: What is WNV, and how is it passed around?

Answer: WNV is a viral disease that can be transmitted by some (but not all) species of mosquitoes here in the Northeast. It’s a disease of humans, horses, and birds. Probably wild birds carry it, mosquitoes pick it up while feeding on the birds, and then mosquitoes transmit it to human beings and animals. While many people may have been exposed to it, only a percentage of them develop any symptoms (similar to the flu) and only a very small percentage of those (less than 1%) have the neurologic form, which can be fatal. So although it’s serious and you should avoid it, there is not a high risk of fatality.

Question: How can I find out where this disease is showing up?

Answer: If you would like to see an up-to-date review of where the risks are, visit the Centers for Disease Control and Prevention (CDC) website’s West Nile Virus page and look at the maps in the middle of the page. You’ll get info on where there have been mosquitoes detected with the virus (this is important because they are the primary means of spreading WNV), but also where there have been human cases. You can find out how many total cases have been reported, versus the number of deaths.

Question: With more WNV around in general, what can I do to avoid getting it?

Answer: The best prevention is to avoid mosquitoes: reduce the amount of stagnant water in which they breed, have effective screens on windows, avoid being outdoors (especially standing still) at dawn and dusk, wear protective clothing, and consider using mosquito repellants if you are outside.

Question: What can I do to protect my animals from WNV?

Answer: The same steps, in general, will help protect animals: reduce the amount of stagnant water on your farm, have screened-in shelters or fly masks/sheets for your animals (especially if they are out during dawn and dusk) and consider using mosquito repellants if other methods don’t work or aren’t practical. An extra step is critical to protect horses: vaccinate. Vaccinations are available, and you should check with your vet about whether and when to vaccinate. Remember, any “first” vaccination needs a booster (repeat) at about a month following the first one; after that, every 6 to 12 months another booster may be advisable. Check with your vet about recommendations in your area.

Question: What about my chickens and pet birds?

Answer: The most sensitive birds to WNV seem to be wild birds of several species, including crows and jays. Chickens appear to be resistant, although WNV has been created experimentally in chickens, geese, and turkeys. For pet birds (such as psittacine birds), screens are the best protection against mosquitoes, as many bird species are highly sensitive to bug repellants. If you have pet birds, it’s a good idea to consult your vet about avoiding WNV.

Question: Are there vaccines for birds?

Answer: There are a number of reports of zoo collections of birds, including some species of geese, many raptors, flamingoes, ratites and penguins, having been successfully vaccinated against WNV using some of the equine vaccines that are available. If you have a valuable collection of birds, you may want to discuss this option with your vet. Use of a vaccine in an off-label manner is likely to result in vaccine-site reactions and abscesses, however, and is never considered completely “safe.” Luckily, chickens appear to be relatively resistant to WNV, and vaccination is not recommended for them.

Question: What about dogs and cats, don’t they get WNV, too?

Answer: Experimentally, it’s been shown that if cats eat WNV-infected mice, they can become infected, but they don’t show illness. As well, an experiment with both dogs and cats showed that inoculating them with WNV resulted in infection, but no signs of illness. Studies of large numbers of dogs and cats in China showed very few with antibodies to WNV, which also supported that our pets can be infected, but probably are resistant to getting sick due to WNV. While it’s a good idea to avoid infection for our pets, the biggest danger of WNV appears to be to humans, horses, and birds.

Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.