Suspected EHD cases in deer at low to moderate level in 2017

SPRINGFIELD – Suspected EHD (Epizootic Hemorrhagic Disease) cases were reported again in Illinois in 2017, but in low to moderate levels. A total of 66 reports were received from concerned landowners and hunters totaling 169 deer from 32 counties, according to the Illinois Department of Natural Resources (IDNR). In comparison, 2012 was the worst year for EHD in Illinois with 2,968 dead deer reported to IDNR from 87 counties.

EHD is a viral disease, spread by biting gnats, which can cause high fever and severe internal bleeding in deer. While often fatal to deer, EHD is not hazardous to humans or pets. EHD-like symptoms in cattle have been reported where EHD has been confirmed in deer. Cattle can be successfully treated with medications. EHD is often confused with bluetongue, a similar disease that can affect sheep and cattle.

EHD was reported at low levels in the southern third of the state, as well as in west central Illinois extending up the Illinois River valley. A more intensive outbreak was reported in the west central Illinois county of Pike (80 cases).

EHD does not impact deer populations evenly across the landscape. A mixture of deer combined with the presence of the virus and midges (biting gnats) that transmit the disease between deer are necessary for an EHD outbreak to occur. Heavy deer mortality can be observed on one farm, while the farm down the road will be hardly affected.

EHD was reported at low levels in the southern third of the state, as well as in west central Illinois extending up the Illinois River valley. A more intensive outbreak was reported in the west central Illinois county of Pike (80 cases).

EHD does not impact deer populations evenly across the landscape. A mixture of deer combined with the presence of the virus and midges (biting gnats) that transmit the disease between deer are necessary for an EHD outbreak to occur. Heavy deer mortality can be observed on one farm, while the farm down the road will be hardly affected.

EHD affects bucks as well as does, adults as well as fawns and yearlings, though individual deer vary in their susceptibility to the virus. Some deer become infected and will be dead within 48 hours, while other deer will be minimally affected. Survivors of infection develop immunity to the virus.

Dead deer are often found near water sources such as lakes, ponds, or streams, though a deer carcass found away from water is also likely to have succumbed to EHD.

EHD-related mortality occurs every year, but becomes more severe during droughty conditions. Limited water sources concentrate deer near exposed mudflats resulting from receding water levels. Midges hatch from these exposed muddy areas, resulting in abundant insect populations.

There is no effective management treatment for this disease. EHD outbreaks end when a heavy frost kills the midges necessary for transmission.

For more information about the EHD in Illinois, contact Doug Dufford, Wildlife Disease and Invasive Species Program Manager with IDNR by email at doug.dufford@illinois.gov or by phone at 815-369-2414.

A table showing the number of reports and cases by county is presented below. A map showing the distribution of EHD-related deer mortality reports in Illinois for 2017 is also presented below.

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