New England States Report Cases of EEE

Four New England states have confirmed 15 cases of Eastern equine encephalitis (EEE) this year; none of the horses survived. This suggests that horse owners should take further measures to protect horses against this deadly disease, such as making sure their horses are vaccinated and reducing mosquito populations.

Eastern equine encephalitis is a mosquito-borne viral disease that affects all equids and progresses rapidly. Clinical signs might include fever, depression, loss of appetite, progressive central nervous system disorders, blindness, and abnormal sensitivity to light and sound. Sudden death can occur at a rate of 75-90%. Vaccines are available, but currently there are no specific treatments for horses with EEE.

A wet, warm spring might have contributed to New Hampshire's nine EEE cases, explains state veterinarian Steve Crawford, DVM. Last year, New Hampshire reported only three equine cases of EEE. "Historically, the disease crops up in large numbers, with lulls of inactivity in between," Crawford says.

Lewis Howe of the Massachusetts Department of Public Health confirmed EEE in four horses. In Rhode Island, an unvaccinated horse was euthanatized and later tested positive for EEE. Maine confirmed the state's first equine case in late September.

Crawford recommends that horses previously unvaccinated for EEE be vaccinated now and boostered in three to four weeks. After that, a booster should be given annually around April or May. "The timing of this booster is important to allow immunity to develop prior to mosquito season," Crawford explained.

Owners also should eliminate standing water, use mosquito repellent and devices such as mosquito magnets, and minimize horse activity/turnout at dusk and dawn when mosquitoes are most active.

Owners should report clinical signs consistent with EEE to a veterinarian immediately.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for .

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