Michigan Horse Succumbs to EEE

Michigan Horse Succumbs to EEE

EEE is spread by mosquitoes, causes inflammation of the horses' brains, and leads to death in many confirmed cases.

Photo: Photos.com

The Michigan Department of Agriculture and Rural Development (MDARD) announced Sept. 15 the first fatality associated with Eastern equine encephalitis (EEE) in an unvaccinated Midland County horse. Lab tests conducted by the Michigan State University Diagnostic Center for Population and Animal Health confirmed the EEE diagnosis. EEE is spread by mosquitoes, causes inflammation of the horses' brains, and leads to death in many confirmed cases.

"There are vaccines available to aid in the prevention of the disease in horses," said Steve Halstead, DVM, Michigan state veterinarian. "These products are safe and effective .... 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

"Horses are sentinels for EEE," Halstead continued. "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."

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. The fatality rate for EEE-affected 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 for 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 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."

A reportable disease in Michigan, EEE 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.

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

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