EEE Confirmed in North Carolina Horse

A 4-year-old horse in Halifax County, N.C., was euthanized recently after contracting Eastern equine encephalomyelitis (EEE), a mosquito-borne disease that is often preventable in horses by yearly vaccination. It is the first reported case of EEE in horses this year in North Carolina.

"The number of reported EEE cases fluctuates each year," said State Veterinarian David Marshall, DVM. "Late summer to early fall is peak mosquito season in North Carolina, and this is right on schedule for us to start seeing cases."

North Carolina had six reported EEE cases in 2010, 23 in 2009, and 13 in 2008. It is estimated that for every reported case, four or more cases go unreported.

The EEE vaccination initially requires two shots, 30 days apart, for horses, mules, and donkeys that have no prior vaccination history. The vaccination does not fully protect the animal until several weeks after the second shot, so vaccinate as early in the mosquito season as possible. Marshall recommends horse owners talk to their veterinarians to determine the best time to start the vaccination process. He also recommends a booster shot of each vaccine be given every six months in North Carolina because of the extended mosquito season.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. The fatality rate for EEE 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.

Thus far in 2011, horses in Florida, New York, and Wisconsin have tested positive for EEE.

People, horses, and birds can become infected from a bite by a mosquito carrying the disease, but there is no evidence that horses can transmit the virus to other horses, birds, or people through direct contact.

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