Mosquitoes that feed on EEE-infected birds can transmit the virus to humans, horses, and other birds. | Photo: iStock

The St. Joseph County horses include a 5-year-old Standardbred mare and a 3-year-old Belgian mare, both of which were reported as unvaccinated and first began showing clinical signs on Oct. 1. The horses’ signs included depression and recumbency (down and unable to rise), and both are deceased.

The Allegan County horse, a 24-year-old unvaccinated Arabian-cross mare, also showed clinical signs beginning Oct. 1, including ataxia (incoordination), inappetence, and walking in circles. She progressed to acting sleepy and became recumbent and unable to rise. The horse was euthanized.

EEE 101

Eastern equine encephalomyelitis is caused by the Eastern equine encephalitis virus, for which wild birds are a natural reservoir. Mosquitoes that feed on EEE-infected birds can transmit the virus to humans, horses, and other birds. Horses do not develop high enough levels of these viruses in their blood to be contagious to other animals or humans. Because of the high mortality rate in horses and humans, EEE is regarded as one of the most serious mosquito-borne diseases in the United States