West Nile Virus 2012 Makes History

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Reports of West Nile Virus causing human health problems highlighted the news in late summer, with Texas considering some widespread spraying to halt the spread of disease in people. In August the Centers for Disease Control (CDC) announced there had been more West Nile virus cases reported in humans than ever before. And, where there are human cases, there will be many more equine cases since this is a mosquito-spread disease. Luckily horses do have safe and efficacious vaccines for WNV.

Dr. Amy Glaser, senior research associate at the Animal Health Diagnostic Center at Cornell University?s College of Veterinary Medicine, emphasizes the problem: ?This year has seen an elevated level of West Nile Virus activity in many geographic areas, including parts of the Northeast, Midwest and Texas.?

Many horse owners thought the drought would slow down mosquito-borne viruses, but it didn't.? Horses who have never received a WNV vaccine should get two doses given two weeks apart. You can assume you have good protection by about 10 days after the second dose. Horses who are receiving a booster dose generally have renewed immunity within a few days after their booster. Foals whose dams were vaccinated should get their initial series at four to six months of age.

The WNV protection can be achieved by using a single vaccine if your horse is already up to date on other vaccines or, more commonly, as part of one of the combo vaccines. If you prefer to spread your horse's vaccines out over the year, June or July is an ideal time to give a WNV/EEE (Eastern Equine Encephalitis) combo vaccine. But, in many areas, it's not too late to protect your horses now.

In addition to vaccinating, avoid having your horses outside at the prime mosquito feeding times of dawn and dusk. Use a fly spray that repels mosquitoes. Encourage birds that eat mosquitoes, such as barn swallows and hummingbirds. Dump water troughs and tanks every other day to prevent larval development. You can also seed ponds with larval-eating fish, dragonfly larvae and BTI or Bacillus thuringiensis israelensis, a bacteria that kills mosquito larvae.

Article by Contributing Veterinary Editor Deb Eldredge, DVM.