Sussex Co., Del., Horse Tests Positive for EEE

Sussex Co., Del., Horse Tests Positive for EEE

Vaccination can increase a horse’s protection against these sometimes fatal diseases, State Veterinarian Heather Hirst, DVM, MS, said.

Photo: Anne M. Eberhardt/The Horse

A horse from Sussex County, Del., has tested positive for Eastern equine encephalitis (EEE), the Delaware Department of Agriculture announced Sept. 19.

The yearling filly was showing signs of severe neurologic disease and was under the care of a veterinarian. Despite receiving supportive care, the horse showed no improvement and was euthanized.

The filly is the third Delaware horse this year to be diagnosed with a mosquito-borne disease. Also this year, two horses have been diagnosed with West Nile virus (WNV); Both have recovered. The last case of equine EEE in Delaware was in 2005.

“With the large mosquito population this year, we continue to urge equine owners to have their horses vaccinated and consult with their veterinarians about maintaining a vaccine program,” said State Veterinarian Heather Hirst, DVM, MS. “Vaccination can increase a horse’s protection against these sometimes fatal diseases. Prevention is still cheaper than care—and far better than having a horse suffer or die.”

Unvaccinated horses are at greatest risk of developing clinical signs from both EEE and WNV, which are spread by mosquitoes and can be fatal. Both horses and humans can contract WNV and EEE if bitten by a mosquito carrying the virus, but it is important to note that the viruses are not transmitted between horses or from horses to people. The viruses normally exist in a cycle between mosquitoes and birds, but occasionally EEE can be transmitted from mosquitoes to mammals.

Hirst said horse owners should contact their veterinarian immediately if they suspect their horse could be showing signs of EEE or WNV. Clinical signs of EEE in horses include fever (102.5-104.5°F), loss of appetite, head pressing, depression or personality change, wobbling or staggering, weakness, blindness, convulsions, and muscle tremors in the head and neck. These signs are also consistent with WNV, although a fever might not be present with WNV.

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