New England States Report Cases of EEE

Three New England states have confirmed nine cases of Eastern equine encephalitis (EEE) in horses this year, and 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 have received EEE vaccinations and reducing mosquito populations around the barn.

A wet and warm spring may have contributed to the New Hampshire's six reported cases of EEE, explains State Veterinarian Steve Crawford, DVM. Officials reported four cases in Rockingham County, one case in Chichester, and one in Boscawen.

Eastern equine encephalitis is a mosquito-borne viral disease that affects all equine species. After infection, the disease progresses rapidly. Clinical signs might include fever, depression, loss of appetite, progressive central nervous system disorders (lack of coordination, chewing movements, head pressing, ataxia, circling, paddling motion of the forelimbs, and convulsions), blindness, abnormal sensitivity to light and sound, and sudden death. The mortality rate in horses ranges from 75-90%. Vaccines are available, but currently there are no specific treatments for horses contracting EEE.

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 said.

According to agency spokesman Lewis Howe, the Massachusetts Department of Public Health (DPH) also confirmed reports of EEE in two horses: one in Haverhill County and one in Wrentham County.

In August, an unvaccinated horse stabled at Lincoln Woods State Park in Providence County, R.I., was euthanized and later tested positive for EEE.

Crawford recommends that horses previously unvaccinated for EEE horses be vaccinated now and followed by a booster shot in 3-4. After this, 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 explains.

However, He warns owners vaccinating their horses for the first time shouldn't expect reliable protection this mosquito season because it will take several weeks for the horse to build protective antibodies against EEE.

Other preemptive measures owners can take to eliminate mosquito infestation include eliminating areas of standing water, using mosquito repellent and devices such as mosquito magnets, and minimizing horse activity and turnout at dusk and dawn when mosquitoes are most active.

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

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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