West Nile Virus (WNV) in Maine 2012: Frequently Asked Questions

Anne Lichtenwalner, DVM, PhD, University of Maine Extension

Question: What are the risks of WNV to humans, horses and pets in Maine this year?

grazing horsesAnswer: WNV is a disease that can be transmitted by some (but not all) species of mosquitoes here in the Northeast. Routine testing of mosquito “pools” has revealed WNV in Maine mosquitoes this summer. Summer weather always brings more mosquitoes, and thus more risk. It’s time to review the steps for preventing disease due to WNV.

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, go to the CDC site (www.cdc.gov/ncidod/dvbid/westnile/index.htm) 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: With more WNV around in general, what can I do to protect my animals?

Answer: The same steps, in general, will help protect animals: reduce the amount of stagnant water on your premises, 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 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 not 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.

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.