As mosquitoes and biting flies emerge this spring, the Wisconsin Department of Agriculture, Trade and Consumer Protection is reminding horse owners that it is time to vaccinate for Eastern Equine Encephalitis and West Nile virus. It also is important to consider testing requirements for Equine Infectious Anemia.

Eastern Equine Encephalitis and West Nile virus vaccination

EEE and WNV are carried by mosquitoes, and vaccinating horses during the spring protects equines before peak mosquito season. In 2019, Wisconsin had five confirmed cases of EEE and no cases of WNV. The state has had up to 24 confirmed cases of each disease in a single year.

EEE and WNV may cause brain inflammation, and equine mortality rates approach 90% for EEE and 30% for WNV. While humans may be infected, the viruses do not pass between people and horses. Transmission occurs when mosquitoes carry viruses from infected birds and bite warm-blooded animals.

Symptoms are similar for both diseases but tend to be more severe with EEE. They include depression, appetite loss, drooping eyelids and lower lip, fever, weakness, twitching, paralysis or lack of coordination, aimless wandering, circling, blindness, seizures, and inability to stand.

While vaccination can be effective, DATCP offers these tips to limit horses’ exposure to mosquitoes:

• Remove items that could collect stagnant water (e.g., old tires, tin cans, plastic containers).

• Keep rain gutters draining properly; turn wading pools and wheelbarrows upside down.

• Clean and chlorinate pools, outdoor saunas and hot tubs; drain water from pool covers.

• Empty and replace water in birdbaths at least once a week.

• Consider keeping horses in the barn from dusk to dawn, when mosquitoes are most active.

Equine Infectious Anemia testing

EIA is a blood-borne viral disease that is potentially fatal and commonly spread by biting insects like horseflies and deerflies, or from sharing equipment contaminated with another equine’s blood. It is important to remember that EIA testing requirements apply to all equids, including donkeys and mules.

Many equine owners run EIA tests annually since changes of ownership and most movement situations require proof of negative tests within the previous 12 months. In 2019, there were two cases of EIA in Wisconsin — the first time in almost 15 years that EIA was diagnosed in the state.

EIA does not affect people, and there is no vaccine or treatment. Symptoms include fever, weight loss, yellowing of body tissue, anemia, swelling of the limbs and weakness; equines may be asymptomatic.

Veterinary care is an essential service under the “safer at home” order, which expires May 26. Veterinarians should evaluate each situation and determine whether treating the animal is essential to its health. To learn more, visit: https://datcp.wi.gov/Pages/News_Media/Covid19AnimalHealth.aspx.