First State Fatality in Eastern Equine Encephalitis

The Michigan Department of Agriculture and Rural Development (MDARD) today announced the first fatality associated with Eastern Equine Encephalitis (EEE) in a Midland County horse. Lab tests conducted by the Michigan State University (MSU) Diagnostic Center for Population and Animal Health (DCPAH) confirmed the EEE diagnosis. EEE is spread by mosquitoes and causes inflammation of the horses’ brains and leads to death in up to 90 percent of the cases.

“There are vaccines available to aid in the prevention of the disease in horses. These products are safe, effective, and can be administered by the owner. Because of the risks associated with our plentiful mosquito populations, and known wild bird reservoirs of the EEE virus, all Michigan horses should be vaccinated. Unfortunately, that was not the case for this horse,” said Dr. Steve Halstead, state veterinarian. “Horses are sentinels for EEE. Reports of illness in horses usually precede illness in people by days or weeks, so the reports serve as early warning that the human population needs to take precautions against mosquitoes.”

Clinical signs in horses include: depression, fever, muzzle weakness, the horse is often down and unable to get up, sweating, dehydration, seizing, grimacing, not feeding, holding the head down, stumbling, blindness, circling, and death. The Midland County horse suffered acute neurologic disease with muscle twitching, a wobbly walk, high temperature, and a dropped head and jaw.

“Last year, 56 horses were confirmed through laboratory testing to have been infected with EEE, although there may have been more since we are aware of 133 horses that died with clinical signs of the disease; however the owners did not seek lab testing,” said Halstead. “The majority of the 2010 affected Michigan horses were not vaccinated against EEE. As was the case in 2010, I encourage reporting of any signs, symptoms or deaths that appear to be related to this illness, even if the owner does not choose confirmatory testing.”

EEE is a reportable disease which also affects poultry such as chickens and emus. Veterinarians are required by law to report cases of EEE. Livestock owners are also encouraged to report cases.

“We encourage diagnostic testing because EEE can look like rabies and while rabies is not common in horses, rabies is contagious from horses to people, and has very serious consequences if not recognized in time” Halstead said.

MDARD encourages horse owners to report suspect cases to the department at 517-373-1077 or, after hours, at 1-800-292-3939.