Deer Diseases

two white-tailed deer at Schiller Woods. Photo by Deep Shah.
Two white-tailed deer at Schiller Woods. Photo by Deep Shah.

The Forest Preserves of Cook County proactively monitors and tests for epizootic hemorrhagic disease (EHD) and chronic wasting disease (CWD) in local white-tailed deer populations.

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Epizootic Hemorrhagic Disease (EHD)

Epizootic hemorrhagic disease (EHD) is an acute, infectious and often fatal viral disease characterized by extensive hemorrhages (severe bleeding). The disease impacts white-tailed deer and other wild ruminants and can cause death within days or hours. It is transmitted to deer by a midge (a species of flying insect) bite and often occurs during extended droughts.


Can humans get EHD?

No, it does not infect humans.


Is it dangerous for other animals?

EHD can be fatal to deer. It is asymptomatic and non-fatal in other wild ruminants, such as elk. It does not infect common pets, such as dogs and cats.


How was the Forest Preserves alerted to the disease in Cook County?

A farmer with property adjacent to the Forest Preserves contacted Resource Management staff in summer 2012 to report dead deer. The Forest Preserves received additional reports from other citizens and visitors during 2012.


How is it diagnosed?

The Forest Preserves’ Resource Management staff, together with the Illinois Department of Natural Resources (IDNR), Cook County and other experts, confirm a diagnosis of EHD after reviewing the epizootic nature of the disease, its seasonal occurrence and its spectacular hemorrhagic lesions. Because of the similarity of its symptoms to other diseases, such as bluetongue and malignant catarrhal fever, the isolation and identification of the virus is essential.


How are the deer infected?

The midge (a species of flying insect) transmits the disease. Once bitten by the midge, infected deer may die within days or even hours.


Has it returned since 2012?

The 2012 outbreak was the first recorded incidence in over 30 years in Northern Cook County. Over 200 deer died during the outbreak. The severity of the 2012 outbreak may have been due to that year’s hot and dry summer.

There has not been a major outbreak since 2012, but there is no way to predict the regularity and severity of outbreaks in the future.


What does it mean to the deer population here?

Because of its very high mortality rate, EHD can have a significant impact on the deer population in a local area. Deer are resilient animals and once outbreaks subside, the local population will return to pre-outbreak numbers rather quickly.


What is the Forest Preserves doing about EHD?

The Forest Preserves works closely with Illinois Department of Natural Resources (IDNR) biologists to monitor the disease and actively tests for EHD and other diseases in dead deer found in Cook County.


What should I do if I come across a dead deer?

Contact the Forest Preserves’ Resource Management Department at 708-771-1180.


Chronic Wasting Disease (CWD)

Chronic wasting disease (CWD) is a fatal neurological disease found in deer and elk. The disease—sometimes called “zombie deer disease” in media reports— attacks the brain causing impacted animals to display abnormal behaviors and lose coordination. Infected deer eventually become emaciated and die.


What are the symptoms of CWD?

Signs of the disease, which may not appear for 18 months or more after infection, include excessive salivation, weight loss, teeth grinding, holding the head in a lowered position and drooping ears. According to the Illinois Department of Natural Resources (IDNR), 94% of the deer in Illinois to test positive for the disease appeared healthy.


What is the Forest Preserves doing about CWD?

The Forest Preserves’ Resource Management Department, working with the
Illinois Department of Natural Resources (IDNR), has a proactive testing process in place for CWD. So far, CWD has not been detected in Cook County.


Can humans get CWD?

Currently, there is no scientific evidence that CWD can infect humans.


What should I do if I come across a dead deer or deer exhibiting signs of CWD?

Contact the Forest Preserves’ Resource Management Department at 708-771-1180.


Where can I learn more about CWD?

Learn more about CWD in Illinois on the Illinois Department of Natural Resources’s CWD webpage.