EEE Confirmed in Van Buren County, Mich., Mare

Michigan Department of Agriculture and Rural Development (MDARD) State Veterinarian James Averill, DVM, confirmed the first case of Eastern equine encephalitis (EEE) in that state for 2013 on Aug. 15. The affected horse is a 12-year-old grade mare from Van Buren County for 2013. The only Michigan case of EEE last year was in an eight-week-old puppy from the same county.

“This horse was never vaccinated against EEE and died after she developed severe swelling of the brain; her clinical signs were stumbling, depression, and blindness,” said Averill. “Horse owners in Michigan’s southwestern counties should be especially aware of the risk and take extra measures to protect their animals.”

The highest concentration of the disease has historically been in Southwestern Michigan. Since MDARD began tracking the disease in 1980, Barry County has had 27 cases, Calhoun County: 22 cases; Cass County: 46; Kalamazoo County: 44; St. Joseph County: 59; and Van Buren County has had 26 EEE cases.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Its fatality rate in horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems. 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.

“In 2010, statewide there were 56 cases of EEE, and since then the cases have steadily declined - more than likely because Michigan veterinarians encourage EEE vaccinations as part of the spring horse vaccination protocol,” Averill said. “Vaccinating at any time against the virus is encouraged, even this late in the year.”

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