The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) and the Wisconsin Veterinary Diagnostic Laboratory confirm that a horse in Barron County tested positive for Eastern equine encephalitis (EEE), Wisconsin’s first confirmed EEE case this year. The 22-year-old quarter horse mare had not been vaccinated against EEE, and was euthanized after showing neurological signs and becoming unable to rise. EEE and West Nile virus (WNV) are transmitted by mosquitoes that carry these viruses which can affect the nervous system, and may be fatal. DATCP encourages horse owners to vaccinate their horses against these viruses to prevent the disease symptoms and high levels of fatality associated with them. EEE is fatal in more than 90% of clinical cases in horses while WNV is fatal in 30-40%.

“From an animal welfare perspective, vaccinating horses against EEE and WNV is necessary to prevent the suffering that occurs once the horse contracts the virus,” said Dr. Julie McGwin, DATCP equine program veterinarian. “While the number of cases of EEE and WNV were down last year compared to the previous year, it is heartbreaking for all involved to see any animal suffer through deteriorating health conditions caused by these viruses. We encourage all horse owners to work with their veterinarian to get their horses vaccinated against these diseases.”

In 2018, Wisconsin had a total of two cases of EEE and three cases of WNV reported. In comparison, Wisconsin had a record 24 confirmed cases reported of each virus in 2017. There are currently no reports of WNV cases this year.

The virus is not contagious between horses. While humans may also be infected by WNV and EEE, the viruses do not pass directly between people and horses. Mosquitoes carry the viruses from infected birds and the only route of transmission is from a mosquito bite.

Because the viruses follow mosquito populations, the threat varies depending on the weather but normally starts in mid- to late summer and remains until the first killing frost. For more information about EEE and WNV including symptoms, the vaccination process, and how to limit exposure to mosquitoes, visit DATCP’s website at  https://datcp.wi.gov/Pages/Programs_Services/HorsesEEEWNV.aspx. DATCP's Division of Animal Health monitors animal health and disease threats, promotes humane treatment of animals, and provides licensing and registration regulation for animals in Wisconsin.


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