The Michigan Department of Agriculture and Rural Development (MDARD) announced Sept. 28 that two additional cases of Eastern equine encephalitis have been diagnosed in horses in Calhoun and Van Buren counties.

The MDARD was notified by the United States Department of Agriculture’s National Veterinary Services Lab in Ames, Iowa, of the results on Sept. 22. Both the Calhoun horse and the Van Buren horse had a positive blood test suggesting EEE exposure and had already been euthanized. These horses had not been vaccinated for EEE.

“These additional cases emphasize the need to protect your horses from mosquito-borne diseases,” said James Averill, DVM, PhD, the MDARD’s state veterinarian. “Animal owners need to take environmental preventative measures against mosquitos and always talk to their veterinarian about vaccination options.”

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care; fatality rates reach 75-80% among horses. Horses that survive might have long-lasting impairments and neurologic problems