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Cumberland County Horse Contracts Eastern Equine Encephalitis

A seven-year-old Cumberland County mare is the first reported case of Eastern Equine Encephalitis (EEE), a serious mosquito-borne illness in horses, in New Jersey for 2021. The mare had not been vaccinated against EEE and was humanely euthanized on August 19, 2021.

“We continue to encourage horse owners be vigilant in vaccinating their animals against these diseases spread by mosquitoes,” NJ Secretary of Agriculture Douglas H. Fisher said. “Vaccinated animals are much less likely to contract deadly diseases such as EEE and West Nile Virus.”

EEE causes inflammation of the brain tissue and has a significantly higher risk of death in horses than West Nile Virus (WNV) infection. WNV is another serious mosquito-borne viral disease that affects a horse’s neurological system. The diseases are transmitted by a mosquito bite. The virus cycles between birds and mosquitoes with horses and humans being incidental hosts. EEE infections in horses are not a significant risk factor for human infection because horses (like humans) are “dead-end” hosts for the virus. Reported animal WNV cases in New Jersey this year have been limited to wild avian species, three Cooper’s hawks and one American crow.

In general, most regions in New Jersey have a reported mosquito population at or slightly above the five-year averages ( The first EEE positive mosquito pool was detected in Gloucester County this year ( Livestock owners are strongly encouraged to vaccinate against WNV, EEE and other mosquito-borne diseases. Effective equine vaccines for EEE and WNV are available commercially. Horse owners should contact their veterinarians if their horses are not up to date on their vaccinations against both EEE and WNV.

For more about EEE in horses, visit

EEE and WNV, like other viral diseases affecting a horse’s neurological system, must be reported to the state veterinarian at 609-671-6400 within 48 hours of diagnosis. The NJ Animal Health Diagnostic Laboratory is available to assist with EEE and WNV testing and can be reached at 609-406-6999 or via e-mail – Learn more about the NJ Animal Health Diagnostic lab at