EEE Case Reports Rolling In

EEE Case Reports Rolling In

The EEE vaccine is on the American Association of Equine Practitioners' list of core vaccines, which are those considered important for every horse to have annually, regardless of geographic location or athletic use.

Photo: Erica Larson, News Editor

Summer might be nearing its end, but reports of confirmed cases of Eastern equine encephalitis (EEE) keep rolling in. According to the U.S. Geologic Survey Disease Maps, updated at 3:00 a.m. on Sept. 4, 77 cases of EEE have been confirmed in 14 states thus far in 2013.

Some of the most recently confirmed cases include:

Massachusetts—The Massachusetts Department of Public Health reported yesterday (Sept. 4) that another horse in the commonwealth had tested positive for EEE; this is the third equine case reported this year. The affected horse was stabled in Tyngsborough (Middlesex County). Massachusetts confirmed five cases of EEE in horses in 2012.

“Mosquitoes remain present in our environment until the first hard frost, so people need to continue to take precautions to avoid getting bitten,” advised DPH State Public Health Veterinarian Catherine Brown, DVM, MSc.

Vermont—Also yesterday, the Vermont Department of Health reported that a Highgate horse was euthanized after contracting EEE. In 2012, two Vermont horses were confirmed positive for the virus.

North of the border, EEE cases have also been confirmed in Canada:

Ontario—The Ontario Ministry of Agriculture and Food (OMAF) released a veterinary update Aug. 27 indicating that a horse from Simcoe County had tested positive for EEE.

"The 11-year-old gelding had an incomplete vaccination history and no history of travel outside the county," the update read. "The horse exhibited acute onset of depression and fever, with some neurological signs; he is reported to be recovering following supportive treatment."

The OMAF indicated that other horses at the affected horse's home premises are "fully vaccinated and are not showing any signs of EEE."

In 2011, Ontario had four EEE cases, with a probable but unconfirmed fifth case. There were no confirmed cases in 2012.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Its fatality rate in horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems.

Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures.

Commercial vaccinations are available to help prevent horses from contracting EEE (See EEE Vaccination Timing Critical for Protection for more information). In the northern regions of the United States, most veterinarians recommend vaccinating horses in the spring prior to peak mosquito levels. In the south, where mosquito populations are present year-round, veterinarians might recommend more frequent vaccination. The EEE vaccine is on the American Association of Equine Practitioners' list of core vaccines, which are those considered important for every horse to have annually, regardless of geographic location or athletic use.

About the Author

Erica Larson, News Editor

Erica Larson, News Editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in three-day eventing with her OTTB, Dorado, and enjoys photography in her spare time.

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