Third Massachusetts Horse Dead from EEE

A third Massachusetts horse has died after being infected with Eastern equine encephalitis (EEE). On Aug. 13 a 3-year-old horse from Lancaster, located in Worcester County, died after developing clinical signs of the illness the previous day.

On Aug. 1 another Worcester County horse died after being diagnosed with the disease, and a Middleborough colt was euthanized on July 21 after developing severe clinical signs of EEE the day prior.

"The most common symptoms of infection with Eastern equine encephalitis are fever, depression, lack of appetite, and neurological signs," said J. Fred Nostrant, DVM, MS, an equine veterinarian practicing in Worcester County. "These neurological signs can range from mild ataxia (incoordination) and depression to circling, head tilting, and aggressive behavior."

EEE is a mosquito-borne illness that affects both horses and humans. It is transmitted by the bite of an infected mosquito. For horses, the disease is often fatal once contracted.

"Unfortunately complete recovery from EEE once the neurological signs are seen is very rare," Nostrant said. "Mortality rates for horses showing neurological signs due to EEE infection are 75-100%, and horses that do survive often have permanent neurological problems."

Elsewhere, two horses in Brooks Country, Ga., tested positive for EEE earlier this year, and more than 69 horses have tested positive for the disease in Florida. Both Virginia and Michigan are also seeing high numbers of horses with positive EEE tests as well.

"EEE is most often seen in the Eastern U.S., east of the Mississippi River," Nostrant said. "We tend to see yearly outbreaks of the disease in New England in the mid- to late summer when mosquitoes are most prevalent. Horses that have been vaccinated within the last six months should be well-protected against EEE, but any means of reducing mosquito populations is helpful in preventing the disease."

Veterinarians are reminding horse owners to vaccinate their horses against EEE annually and to use topical or feed-through insect repellents to limit the horse's exposure to mosquitoes. Officials are urging farm owners to help control the mosquito population in their area by ridding their property of standing water, where mosquitoes lay their eggs.

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 eventing with her OTTB, Dorado.

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