Epizootic hemorrhagic disease (EHD), which is spread by a biting insect called a midge, is a viral disease that occurs naturally and can infect white-tailed deer.
The disease was not found in Minnesota wild deer until September 2019 but it is common in the Midwest. Wisconsin, Nebraska, Iowa, Illinois, Michigan and Ohio report EHD mortalities almost every year.
The disease can dramatically reduce a local deer population in the short-term but has a relatively small impact on the overall deer population. The midge occurs naturally, and there is no known management activity to combat the disease.
EHD is not a threat to humans or animals outside the deer family. Even so, people should not consume deer that appear to be sick or in poor health.
EHD is seasonal and most often occurs during drought-like conditions in the late summer and early fall. Frost will kill the virus and midge that carries it, ending the potential infection period.
A female midge of the Culicoides genus (commonly called a no-seeum) picks up the virus from the blood of an infected host and transmits the virus by biting another host. The disease cannot be transmitted deer-to-deer and does not remain on the landscape.
The incubation period is 5-10 days and most die within 36 hours after clinical symptoms appear.
Finding seemingly healthy multiple deer dead near water is typical of an EHD die-off. Fever drives the animals to seek water and they die from internal lesions and hemorrhages.
EHD has circulated in the southern United States for decades and outbreaks in deer there are typically mild or completely inapparent, detectable only by antibody blood testing.
The periodic movement of the EHD virus to the northern United States, where there is little history of previous exposure, can result in severe outbreaks with high localized mortality.
EHD in Minnesota
- October 2012: A sick cow was diagnosed with EHD in Springfield, Minnesota.
- A past DNR research study showed positive EHD results in antibody testing of deer in Cook County.
- October 2018: The Board of Animal Health (BAH) detected the first occurrence of the disease in deer when test results confirmed EHD in six captive deer on a Goodhue County farm.
- September 2019: BAH testing confirmed two farmed deer in Houston County on Sept. 5.
- September 2019: EHD was first discovered in Minnesota wild deer when DNR confirmed that four deer in a three-square mile area near St. Stephen in Stearns County were infected. Additional deer in the area are suspected to have died from the disease but were too decomposed for testing.
- September 2019: DNR confirmed that a deer near Caledonia in Houston County in southeastern Minnesota died from EHD. Additional deer in the area are suspected to have died from the disease.
- U.S. Deparment of Agriculture - Animal and Plant Health Inspection Service
- Iowa State University - The Center For Food Security & Public Health
- Cornell Wildlife Health Lab
- Michigan DNR