Mosquito-Borne Eastern Equine Encephalitis Found in Three Michigan Horses

(edited from a press bulletin)

Yesterday the Michigan departments of Community Health (MDCH) and Agriculture (MDA) received confirmation from the Michigan State University (MSU) Diagnostic Center for Population and Animal Health (DCPAH) that a three month old Percheron filly from Calhoun County and a 12 month old Arabian colt from Barry County tested positive for the mosquito-borne disease Eastern Equine Encephalitis (EEE).

MDA has also been informed that several additional horses in Cass County are highly suspect for EEE and are pending test results.

MDA was notified on July 20, 2010 of a third case from a four-year-old mixed breed mare from Cass County by the National Veterinary Services Laboratories. This horse was also displaying signs of neurologic disease typical of EEE, including staggering and depression, as well as fever.

“We are concerned about this finding of EEE in southwest Michigan and the likelihood of additional cases, so it’s imperative people take every precaution possible to prevent mosquito borne disease exposure for themselves and their livestock,” said Dr. Steven Halstead, State Veterinarian. “A simple vaccination will protect your animal from these often fatal illnesses, and routine measures to reduce mosquito exposure and eliminate mosquito habitats around the home and farm will help protect people, horses, and other livestock. Horse owners should consult their veterinarian regarding measures appropriate for their herd.”

EEE is caused by viruses found in wild birds. Mosquitoes that feed on birds infected with EEE can transmit the disease to humans, horses, and other birds. Some birds are able to harbor the EEE viruses without becoming acutely ill, thereby serving as reservoirs for the disease. Horses do not develop high enough levels of these viruses in their blood to be contagious to other animals or humans. Because of the high mortality rate for horses and humans, EEE is regarded as one of the most serious mosquito-borne diseases in the United States.

Tips for preventing mosquito-borne diseases include:

? Avoid mosquito bites: Use insect repellent when outdoors, especially from dusk to dawn.

? Look for EPA-labeled products containing active ingredients, such as DEET, Picaridin (KBR3023), or oil of lemon eucalyptus (p-menthane 3,8-diol).

? Apply more repellent, according to label instructions, if mosquitoes start to bite.

? Mosquito-proof homes: Fix or install window and door screens and cover or eliminate empty containers with standing water where mosquitoes can lay eggs.

? Protect your horses: Commercially available licensed vaccines against EEE are recommended for all horses in the U.S. Horses should be vaccinated annually. It’s not too late this year to vaccinate your horses

? Use approved insect repellants to protect horses.

? If possible, put horses in stables, stalls, or barns during the prime mosquito exposure hours of dusk and dawn.

? Eliminate standing water and drain water troughs, and empty buckets at least weekly.

Seasonal activity varies from year to year, but mosquitoes carrying EEE remain a threat.

For more information about EEE in horses, consult your local veterinarian. Michigan residents should contact MDA’s Animal Industry Division at 517-373-1077; or visit the MDA website at:

Bloody mosquito illustration by Zoran Ozetsky. Thanks!by Fran Jurga | 27 July 2010 | The Jurga Report at Follow @FranJurga on for more horse health news!




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