Four cases of Eastern equine encephalitis (EEE) were recently confirmed in two neighboring west Michigan counties, and another in the northeast corner of the Michigan’s Lower Peninsula. The disease was also confirmed in three of seven free-ranging white-tailed deer, making Michigan only the second state in the country to detect EEE in cervids. Steve Halstead, DVM, Michigan state veterinarian, suggests that it is not to late in the season for horse owners to take measures to protect horses against this deadly disease, such as making sure their horses have received EEE vaccinations and reducing mosquito populations around the barn that spread the disease.

Three equine cases of EEE were confirmed in Kent County during September and one in Montcalm County on Oct. 1. The deer were found in both counties. All five horses and seven deer died as a result of the disease.

Eastern equine encephalitis is not as common in Michigan as it is in southern states, although we consider it to be endemic and always a threat. “We didn’t have any cases reported last year, and in 2003 only three cases had been reported,” Halstead said. “Interestingly, two of those three cases were also co-infected with West Nile Virus (WNV).”

Halstead said that 2002 was the biggest year for mosquito-borne viruses in Michigan. Although only one equine case of EEE was confirmed in Michigan in 2002, 341 WNV cases were confirmed. As of Oct. 11, there had been 21 cases of WNV in 14 counties