First Eastern Equine Encephalitis Case for New Jersey in 2025

(TRENTON) – The first confirmed case of Eastern Equine Encephalitis (EEE) in 2025 was detected in a 3-year-old gelding in Burlington County. With symptoms including, front and rear ataxia, muscle fasciculation, disorientation, and inability to rise , the horse was euthanized on October 17, 2025. The horse was unvaccinated and had an unknown vaccination history against the disease.

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 a 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, meaning they will not transmit the disease.New Jersey has a reported mosquito population this season that is near the 5-year average; however, there was an increase in EEE positive mosquito pools starting in mid-September. 

The first EEE-positive mosquito pool was detected in Atlantic County this year (https://www.nj.gov/health/cd/statistics/arboviral-stats/). EEE-positive mosquito pools have also been found in Burlington, Camden, Cape May, and Morris counties. 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.“We continue to encourage horse owners to be vigilant in vaccinating their animals against these diseases spread by mosquitoes,” New Jersey Secretary of Agriculture Ed Wengryn said. “Vaccinated animals are much less likely to contract deadly diseases such as EEE and West Nile Virus.”

The EEE diagnosis was confirmed with testing at the NJDA’s Animal Health Diagnostic Laboratory.For more information about EEE in horses, visit the New Jersey Department of Agriculture website at: https://www.nj.gov/agriculture/divisions/ah/livestockhealth/diseaseworksheets.shtmlEEE and West Nile virus, 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 New Jersey Animal Health Diagnostic Laboratory is available to assist with EEE and WNV testing and can be reached at 609-406-6999 or via email – jerseyvetlab@ag.nj.gov. Learn more about the NJ Animal Health Diagnostic lab at www.jerseyvetlab.nj.gov.

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