Katie Hennessy

Protect Your Horse From Eastern Equine Encephalomyelitis

Eastern equine encephalomyelitis (EEE) is caused by a virus that creates inflammation of the brain and spinal cord and is transmitted mostly via mosquitoes. Luckily EEE is a rare disease, but it’s one of the most dangerous mosquito-borne viral diseases because of its high mortality.


The EEE virus attacks the central nervous system of horses with sudden onset of signs including fever, dullness, muscle twitching and weakness before recumbency and death of the infected animal. Death occurs in over 90% of cases within just 3 days of when signs start. Infected horses do not have enough virus in their blood to be contagious to other animals or people so they do not need to be quarantined.


Luckily, there is a vaccine available with an excellent protection rate against EEE. Horses that receive a complete vaccine protocol with appropriate boosters have a minimal chance of developing the disease and tend to show less severe illnesses than unvaccinated animals. In addition to vaccination, you can reduce your horse’s exposure to mosquitoes by eliminating breeding areas for mosquitoes (stagnant water) and using insect spray or sheets. 


Please schedule routine vaccination appointments with your veterinarian to keep your horse protected. Once clinical signs are noticed, it is usually too late to save the horse. Suspected and confirmed cases of EEE must be reported to the State Veterinarian’s Office, if you have any concerns about your horse please contact your veterinarian immediately.

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