EEE Found In Michigan Horse

Michigan Department of Agriculture (MDA) Director Dan Wyant today announced that the first reported case of Eastern Equine Encephalitis (EEE) this year has occurred in a horse in Barry County. This diagnosis was based on clinical signs and laboratory evaluation of brain tissue conducted by the Animal Health Diagnostic Laboratory at Michigan State University.

This follows the report last week that the EEE virus had been detected in mosquitoes from Gladwin County and from juvenile wild birds in Kalamazoo County. These detections indicate the presence of EEE virus in those areas and possibly other areas of southern Michigan.

Clinical signs of EEE (also known as sleeping sickness) in horses include fever, progressive muscle incoordination, paralysis, blindness, and an inability to rise. The fatality rate for this disease in horses often reaches 95 percent. Human infection with the EEE virus is rare in Michigan and is characterized by a high fever progressing rapidly to coma.

Horses and humans contract EEE from mosquitoes that have fed on birds that carry the virus. Birds are able to harbor the virus without becoming acutely ill and serve as a reservoir for EEE. Horses do not develop a high enough level of the virus in their blood to be contagious to other animals or humans. Horses that contract EEE, however, indicate that the virus is in a particular region and should serve as a warning to residents to avoid being bitten by mosquitoes.

"People can avoid the risk of EEE by taking reasonable precautions to prevent being bitten by mosquitoes," said Dr. Mary Grace Stobierski of the Michigan Department of Community Health. "Avoid areas where mosquitoes are prevalent, particularly during evening hours when they are most active, use insect repellent when it is necessary to be out-of-doors, and repair defective window and door screening to keep mosquitoes out." The mosquitoes that are most likely to carry the EEE virus are found near swamp areas in rural and suburban areas.

EEE does not occur in Michigan every year; however, when it does occur it can be fatal to humans and horses. Four human victims have died in Michigan since 1980, the most recent in 1997. Since 1980, 254 horses in Michigan have died from EEE.

Michigan has an active EEE Surveillance Program that involves a cooperative effort between MDA, the Michigan Department of Community health, Michigan State University, 22 local health departments, nearly five dozen veterinary practices, and four county-wide mosquito control programs. The EEE Surveillance Program identifies and confirms cases of EEE in horses, traps and test mosquitoes, identifies and tests wild bird flocks, and monitors suspect human cases.

Detecting EEE is important because the disease is fatal in 90 to 95 percent of infected horses and 60 percent of infected humans. Michigan physicians are encouraged to submit specimens from suspect human cases to the Michigan Department of Community Health Reference Laboratory in Lansing where a rapid test is available to rule out this disease in humans.

A vaccine is available to prevent EEE in horses, but vaccination is neither readily available nor practical for routine human use. Horse owners should contact their veterinarian to discuss vaccination against EEE. Veterinarians should report all suspect EEE cases to MDA's Animal Industry Division at 517/373-1077. Physicians should immediately report all suspect human cases to their local health departments.

The Michigan Department of Agriculture is the official state agency charged with serving, promoting and protecting the food, agriculture and agricultural economic interests of the people of the State of Michigan. MDA supports agriculture, Michigan's second-largest industry.

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