Equine Vaccinations Encouraged for Mosquito-Borne Diseases

Equine Vaccinations Encouraged for Mosquito-Borne Diseases

By Dr. Julie McGwin, Wisconsin Department of Agriculture, Trade and Consumer Protection

This has been an active year for mosquitoes in Wisconsin. Unfortunately, mosquitoes are the vector for Eastern Equine Encephalitis (EEE), a viral illness that can affect many different species, including horses and other equines, birds, and humans.

As of October 9, 24 laboratory-confirmed equine cases of EEE were identified in Wisconsin, mostly across the northern part of the state. Equine practitioners report many more unconfirmed cases of EEE in their practice areas. The Wisconsin Department of Health Services (DHS) considers either a Polymerase Chain Reaction (PCR) test or an IgM Capture ELISA test to be diagnostic for EEE. DHS has reported two human cases of EEE in 2020 – one from Eau Claire County and one from Chippewa County. The Chippewa County case was fatal. Michigan and Massachusetts have also reported human EEE fatalities.

There are effective equine vaccines available for both EEE and West Nile Virus (WNV), another reportable mosquito-borne disease affecting equines and other animals, including humans. Thanks to recent frosts, the Wisconsin mosquito season is winding down for 2020, but equine vaccinations should be encouraged next spring prior to mosquito season. The American Association of Equine Practitioners (AAEP) considers both EEE and WNV vaccines to be core vaccinations. Horses require two vaccinations three to four weeks apart and an annual booster. Please remind clients to employ methods to minimize mosquito exposure using repellents and control measures both now and in the future.

EEE is fatal in approximately 90 percent of equine cases. Clients should contact their veterinarians if their horses exhibit clinical signs of illness. For both EEE and WNV, the symptoms are generally neurologic, progressing to recumbency and the inability to rise with EEE. If horses become non-ambulatory, the prognosis is grave and humane euthanasia may be indicated due to welfare concerns.

Information about EEE and WNV, including a list of the counties with laboratory-confirmed equine cases, can be found on the Wisconsin Department of Agriculture, Trade and Consumer Protection website by clicking here.



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