Epizootic hemorrhagic disease in deer
Epizootic hemorrhagic disease is an infectious and often fatal viral disease in white-tailed deer. Learn about the disease, how it spreads, its potential impact and what we are doing.
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About Epizootic hemorrhagic disease (EHD)
Epizootic hemorrhagic disease (EHD) is an infectious and often fatal viral disease in white-tailed deer and occasionally other ruminants (such as sheep and cattle) that causes extensive internal bleeding.
Midges of the genus Culicoides (a small flying insect common known as “no-see-ums”) are the most common known carrier of the virus. Deer can only contract EHD through the bite of a midge carrying the virus. EHD does not spread from deer to deer.
EHD is one of the deadliest diseases to affect white-tailed deer in the United States. To date, EHD has been confirmed several times in Ontario:
- September 2017 in two white-tailed deer near London, Ontario
- October 2021 in three white-tailed deer near Kingston, Ontario
- October 2021 in one white-tailed deer near Amherstburg, Ontario
It’s important for deer hunters, wildlife managers, farmers and livestock owners to know about EHD. It is a serious disease with the potential to cause large-scale outbreaks in wild animals, however outbreaks of EHD are usually short-lived and do not pose a long-term threat to deer populations.
Signs and symptoms of EHD
Deer can develop signs of EHD in as little as seven days. Infected deer typically exhibit signs and symptoms such as:
- loss of appetite
- loss of fear of people
- excessive salivation
- rapid pulse and respiration rate
- signs of fever, including submersing themselves in bodies of water to reduce their body temperature
- a blue tongue from hemorrhaging and lack of oxygen in the blood due to the effects of the virus
- swelling of neck and head or otherwise unhealthy appearance
- many infected deer may be found in one place, or in close proximity
Deer with an acute form of the disease may go into shock 8–36 hours after the onset of symptoms and are often found dead in or near water bodies.
EHD versus Chronic Wasting Disease
Some signs of EHD may be confused by hunters or the public as being due to Chronic Wasting Disease. Chronic Wasting Disease has not been detected in Ontario wildlife.
Unlike animals with EHD, those with Chronic Wasting Disease will exhibit:
- being thin or weak
- no head/neck swelling
- no blue tongue
- deer are usually found alive, but symptomatic, or in some cases dead alone
When does EHD occur
EHD outbreaks typically happen in late summer to early autumn. Experts believe the spread of infected midges over great distances is assisted by strong winds.
Climate change (warmer temperatures, shorter winters) may increase the chances of EHD outbreaks in Ontario. Long periods of hot weather can extend the breeding season of midges and may also extend the period when the virus can be transmitted.
Where present, the virus may affect deer each year to varying degrees depending on environmental conditions. Midges are killed off with the onset of cold late fall frost and winter weather.
Currently no effective treatments or vaccines for EHD are available.
What we are doing
We are working with the Canadian Wildlife Health Cooperative to monitor EHD in Ontario.
What you can do
You can help reduce midge larvae by eliminating standing water such as old tires, planters, flowerpot saucers, buckets, trash containers, and by replacing water in bird baths frequently. This can also help reduce the numbers of the biting insects responsible for carrying this virus.
Report dead or sick wildlife
If you encounter sick or suspiciously dead wildlife, contact the Canadian Wildlife Health Cooperative at
Individual landowners are responsible for the cleanup of their own property. In most cases, dead wild animals can be put in the garbage or buried. Each municipality has different rules for the disposal of wildlife carcasses. Call your local city or town for more information. Municipalities are responsible for the public properties that they own (such as municipally owned public beaches).
There are no human health concerns from bites to humans from midges carrying the EHD virus.
Eating meat from EHD-infected deer that is free from signs of sickness, ulcers, abscess, or other abnormalities is considered safe.
Hunters should, as always, practice proper carcass handling and processing techniques when dressing hunted deer.
Handling wildlife carcasses
As part of normal good practices when handling and processing deer, it is suggested that hunters:
- wear rubber gloves when field dressing carcasses
- minimize the handling of brain and spinal tissue
- minimize the handling of bones of the skull and spinal cord
- do not consume the brain, spinal cord, eyes, spleen, tonsils or lymph nodes of harvested animals