Horse Owners Regret Decisions: Affordable Vaccine Could Have Saved Horses' Lives

Vaccinations protect against mosquito-borne disease like West Nile virus (WNV) and Eastern Equine Encephalomyelitis.

July 11, 2012–Last summer, when Becky Myszka, DVM, arrived at many farms, it was already too late. It was a scene that repeated itself over and over. The horse owner had called the Wisconsin Valley Veterinary Services describing an odd scenario. The horse had been fine, but perhaps a little quieter than normal. During the last day or so, the horse started stumbling. In the worst of the cases, the horse was down and couldn’t get back up. Dr. Myska’s diagnosis in each of these cases: Eastern Equine Encephalomyelitis (EEE). It’s a disease with a 90 percent mortality rate,1 so horse owners facing EEE are more than often facing the loss of their equine companion.

“It’s really disheartening to see cases of EEE, especially since there are vaccines available and they are very effective,” says Dr. Myszka. “We always recommend that our clients vaccinate their horses against EEE, Western Equine Encephalomyelitis (WEE), West Nile virus (WNV), rabies and tetanus. A combination vaccine that covers all those diseases except rabies is very affordable.”

Horse owners shared a variety of reasons with Dr. Myszka about why they hadn’t vaccinated against EEE. ?In some cases, the owner hadn’t vaccinated because he or she erroneously believed that since the horse never came into contact with other horses, it wouldn’t be able to contract the virus. However, EEE is transmitted by infected mosquitoes, making it possible for exposure to occur anywhere.2 In other cases, the owners had opted to vaccinate only their more valuable horses or none at all due to limited finances.

“I think most horse owners we talked to were aware of the disease and the option to vaccinate,” she says. “People get lulled into a sense of complacency when they haven’t heard about a particular disease being diagnosed in their area. But I believe since we experienced so many cases last year, horse owners would be wise to vaccinate.”

In 2011, in addition to the 33 confirmed cases3 in Wisconsin, EEE was reported in Michigan, Florida, New York and Louisiana.4 So far, in 2012, three cases have been reported in Florida.5

“With the mild winter, the mosquito season is starting earlier this year. As the temperatures around the country increase, along with perhaps a larger than normal mosquito population, we have the potential to see more cases of EEE,” says April Knudson, DVM, equine specialist for Merial’s Large Animal Veterinary Services. “We know horse owners want to provide the best care possible for their horses and vaccinating against equine diseases is one of the most important things they can do. Although some cases have already been reported, it isn’t too late to vaccinate.”

Merial’s RECOMBITEK? rWNV-EWT combination vaccine offers protection against not only EEE, but also WNV, WEE and tetanus. Following initial vaccination, horses need to be revaccinated annually to help safeguard against disease.6

While vaccination is the best way to defend against equine diseases like EEE, horse owners can also minimize the mosquito population around their farms by employing these practices:

  • Eliminating standing water.7
  • Emptying or changing the water in bird baths, fountains and plant trays regularly.7
  • Draining or filling temporary pools of water with dirt.7
  • Keeping lights off in the barn or switching to yellow “bug” lights which tend to attract fewer mosquitoes.7
  • Using mosquito repellant spraying systems in the barn.

An additional tool horse owners have at their fingertips is Merial’s free Outbreak Alert program. The program tracks reported cases of WNV, EEE, WEE, Equine Herpesvirus, rabies, equine influenza and Potomac horse fever as they are confirmed around the country. Those who have signed up for the service receive texts and/or email messages notifying them of confirmed disease threats in their areas. Owners who travel with their horses can enter multiple ZIP codes in the site’s search field to help them stay abreast of disease threats throughout the country. There are also veterinarian-exclusive features available, including printable materials veterinarians can share with their clients.

To learn more about EEE, other equine diseases and vaccination guidelines, or to sign up for Outbreak Alert, visit

About Recombitek rWNV-EWT
Recombitek rWNV-EWT vaccine is a combination vaccine labeled to aid in the prevention of disease and viremia due to West Nile virus and encephalitis caused by Eastern Equine Encephalomyelitis Virus (EEEV) and Western Equine Encephalomyelitis Virus (WEEV) and tetanus caused by the Clostridium tetani toxin.5

?RECOMBITEK is a registered trademark of Merial Limited. ?2012 Merial Limited, Duluth, GA. All rights reserved. EQUIBWV1204 (05/12)

1Eastern/Western equine encephalomyelitis. American Association of Equine Practitioners. Available at: Accessed May 14, 2012.

2Mosquito Borne Diseases: Eastern and Western Equine Encephalomyelitis and West Nile Virus – Prevention is Just a Vaccine Away. Department of Animal Science. University of Connecticut. Available at: Accessed May 14, 2012.

3Animal Health Update. News from the Wisconsin State Veterinarian. October 2011. Available at:

4United States Department of Agriculture, Animal and Plant Health Inspection Service. Available at: Accessed May 14, 2012.

5Florida Department of Health. Florida Arbovirus Surveillance. Available at: Accessed May 15, 2012.

6RECOMBITEK rWNV-EWT product label.

7United States Environmental Protection Agency. Methods of mosquito control. Available at: Accessed May 15, 2012.

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