Epizootic Hemorrhagic Disease

The Wildlife Management division of the Forest Preserve District of Cook County, together with the Illinois Department of Natural Resources, has identified an outbreak of Epizootic hemorrhagic disease (EHD), an acute, infectious, often fatal viral disease of some wild ruminants, particularly deer, in Northwest Cook County.


For more information on EHD in Cook County, read the FAQ below, or this article from the Chicago Tribune.


What is EHD?

Epizootic hemorrhagic disease (EHD) is an acute, infectious, often fatal viral disease of some wild ruminants, particularly deer. The disease is characterized by extensive hemorrhages and can cause death within days or hours.


Is it contagious to humans?

No, it does not infect humans.


Is it dangerous for other animals?

EHD has proven to be fatal to deer. While it can be transmitted to other wild ruminants such as elk and moose, it is asymptomatic and non-fatal. Other animals, such as dogs and cats, are not infected.


How was the District alerted to the outbreak?

District Wildlife staff was initially contacted by a farmer on adjacent property, who had several dead deer on his land. We have since received reports from other citizens and Preserve visitors.


How was it diagnosed?

The District’s Wildlife Management staff, together with the Illinois Department of Natural Resources and other experts, confirmed the 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 disease is transmitted by the midge (a flying insect). Once bitten by the midge, infected deer may die within days or even hours.


How many deer have died and how many do we speculate may die?

The number of deer at this point is approximately 90, as of August 23, 2012. Biologists indicate that it would be impossible to predict the extent of future mortality in the local deer herd because the natural history of the vector, midge, is poorly understood.


Will it be back next year?

We believe that it is highly unlikely that we will see an outbreak next year in this area. This outbreak is the first recorded incidence in over thirty (30) years in Northern Cook County and is attributed in large part to the exceptionally hot and dry summer season.


What does it mean to the deer population here?

Because of its very high mortality rate, EHD can have a significant effect upon the deer population in a local area, reducing numbers drastically. At this point, it’s too soon to speculate on the final number of deer impacted. Deer are resilient animals and we expect that once the outbreak subsides, the population will return to pre-outbreak numbers rather quickly.


What is the Forest Preserve District doing about it?

The District is working closely with Illinois Department of Natural Resources biologists to monitor the outbreak to determine the extent of the affected population.


Can we protect the deer?

We are not able to do anything to prevent the disease from affecting the deer population. We anticipate that the outbreak will subside after the first frost, which will kill the midge, generally in mid-October.


What should we do if we come across a dead deer on Forest Preserve District property?

Contact the Forest Preserve District’s Department of Resource Management at 708-771-1180/1335.

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