A 15-year-old mare in Atlantic County has been confirmed as a case of Eastern Equine Encephalitis (EEE), a severe mosquito-borne illness affecting horses, according to the New Jersey Department of Agriculture. This marks the first reported instance of EEE in a New Jersey horse for 2024. The mare exhibited symptoms including fever, ataxia, and an inability to rise before succumbing to the disease on August 3, 2024. The horse had received a vaccination on July 29, 2024; however, its prior vaccination history is unknown.
EEE causes brain tissue inflammation and carries a higher mortality risk in horses compared to West Nile Virus (WNV), another mosquito-borne viral disease that impacts the neurological system of horses. Both diseases are transmitted through mosquito bites and involve cycles between birds and mosquitoes, with horses and humans serving as incidental hosts. Notably, EEE infections in horses do not pose significant risks for human infection since both species are “dead-end” hosts for the virus.
In New Jersey, most regions report mosquito populations near their five-year average. The first EEE-positive mosquito pool this year was identified in Cape May County. Additional positive pools have been detected in Morris and Union counties.
Livestock owners are urged to vaccinate against WNV, EEE, and other mosquito-borne diseases using commercially available equine vaccines. Horse owners should consult their veterinarians if their animals are not current on vaccinations against these diseases.
“We continue to encourage horse owners to be vigilant in vaccinating their animals against these diseases spread by mosquitoes,” said New Jersey Secretary of Agriculture Ed Wengryn. “Vaccinated animals are much less likely to contract deadly diseases such as EEE and West Nile Virus.”
