Mosquito-Borne Illness Kills South Jersey Horse, 2nd This Year

SALEM COUNTY, NJ — A Salem County horse was euthanized after catching a serious mosquito-borne illness, officials said Monday. The Standardbred mare had South Jersey's second-known case of Eastern Equine Encephalitis (EEE) in horses this year.

EEE causes inflammation of the brain tissue and carries a "significantly" higher risk of death in horses than West Nile virus, according to the New Jersey Department of Agriculture (NJDA). Both diseases are transmitted through a mosquito bite. The virus cycles between birds and mosquitoes, with horses and humans being incidental hosts, officials said.

Horses, like humans, are "dead-end" hosts to EEE, so infections in horses don't present a significant risk for human infection, the NJDA said.

The mare with EEE was humanely euthanized Oct. 13, according to the NJDA. Its vaccination status is uncertain, officials said Monday.

Only 11 human cases, on average, get reported annually around the nation, according to the CDC.

A Gloucester County horse with EEE was euthanized in September. Authorities haven't identified the disease in any other New Jersey horses this year. Read more: Gloucester Co. Horse Contracts Mosquito-Borne Illness, First In 2023

Most regions of the state have a reported mosquito population near the five-year average, according to New Jersey data. West Nile virus has been most prevalent in humans, with 13 cases and one death identified from mid-July through mid-September around the state. Overall, 837 mosquito pools around the state tested positive for the virus this year.

Meanwhile, 18 mosquito pools have tested positive this year for EEE, according to the New Jersey Department of Health. No human cases in New Jersey have been detected in 2023.

The NJDA urged livestock owners to vaccinate against EEE, West Nile virus and other mosquito-borne illnesses. Effective equine vaccines for both diseases are available commercially, the state agency says.

Horse owners should contact their veterinarians if their hoses aren't up to date on vaccinations for EEE or West Nile virus.

"Vaccinated animals are much less likely to contract deadly diseases such as EEE and West Nile virus," said Joseph Atchison III, the state's assistant secretary of agriculture.

EEE and West Nile virus — like other viral diseases affecting a horse's neurological system — must be reported within 48 hours of diagnosis to the state veterinarian at 609-671-6400. The New Jersey Animal Health Diagnostic Laboratory can assist with testing and can be reached at 609-406-6999 or jerseyvetlab@ag.nj.gov.

Learn more about EEE from the NJDA and the state health department.