EHD In Deer or Epizootic Hemorrhagic Disease

Watch Out For EHD in Deer Outbreaks

Epizootic Hemorrhagic Disease (EHD) is an infectious virus and can be fatal for deer. While it mainly affects white-tailed deer, it has also been found in other types of deer. These types include mule deer and pronghorn antelope. So, it is essential to keep an eye out for it and know what to look for to prevent it from spreading and affecting livestock.

Here is what you should know about this disease. We’ll outline exactly what it is, how it spreads and what you can do if you suspect a deer has EHD.

What Is Epizootic Hemorrhagic Disease or EHD In Deer?

As the name suggests, Epizootic Hemorrhagic Disease is a hemorrhagic disease that primarily affects white-tailed deer. It is caused by an infection of an Orbivirus – the Epizootic Hemorrhagic Disease Virus (EHDV) to be exact.

This virus is spread by biting flies, midges, or gnats – but we’ll go into more detail about the transmission of EHD later on. The disease is infectious and can be deadly as it causes extensive hemorrhages. To put it simply, it causes blood vessels to break and bleed.

EHD results in a high fever and makes the deer thirsty. Thus, many victims of this disease are found near or even in water sources.

Luckily, this disease does not affect humans. Although, it is still best to avoid eating any animals that were unhealthy or disoriented before being harvested.

(EHD) Epizootic Hemorrhagic Disease vs Bluetongue Disease

Two different viruses cause hemorrhagic disease in deer.

The first is the Epizootic Hemorrhagic Disease virus and the second is the bluetongue virus (BTV).

While these are often confused, they are not the same thing and it’s important to understand the difference.

Both of these commonly affect white-tailed deer and are transmitted through the bites of midges, gnats, or “no-see-ums”. Neither of these diseases has been shown to affect humans, but they both cause significant fatalities in white-tailed deer populations.

Bluetongue virus or BTV

Bluetongue virus is very similar to EHDV because they are closely related. As such, livestock with BTV present very similar clinical symptoms – making the two viruses very easy to confuse and misdiagnose.

BTV is very serious in cattle, sheep, goats and other ruminants. It can have an impact on international trade. So, it is vital to put prevention measures in place when this disease is suspected. It can also potentially infect dogs.

Although EHD in deer is most common in whitetails, outbreaks have been reported in cattle. However, it is very rare for cattle to show any serious symptoms or die from the disease. The same goes for sheep.

If you suspect your livestock or deer of having one of these diseases, you will need to test at an animal health laboratory to distinguish between the two viruses.

How Is EHD Spread In Deer?

EHD is found throughout the United States. It can also be found in Australia, Africa, and Asia. Because it is transmitted through biting flies or midges, the distribution and outbreaks of the virus are dependent on the abundance of the midges in an area. This means that both EHD and BTV affect deer populations locally.


Outbreaks are more common in the southern United States, with frequent, mild occurrences. On the other hand, EHD is less common and more severe in the northern states and presents higher mortality. Once again, because this depends on the midge populations, the spread to deer is not uniform.

Insect Bites

As mentioned, biting midges or gnats transmit this virus and infect deer (and livestock) by biting them. Deer cannot infect one another once they have the virus as it is spread by a vector. Luckily, this means that you can lessen the frequency of outbreaks by taking precautions to limit the abundance of midges. We’ll get into some prevention tips later, though.

Typical Spikes in Transmission

EHD and BTV outbreaks usually spike during late summer or early fall – especially in dry spells. When there is drought, water sources shrink. This results in small pockets of warm, stagnant water, which makes the perfect breeding ground for midges and gnats.

Unfortunately, deer also then congregate around these areas to find water during droughts. Thus, it’s easy for them to get bitten and contract the disease. It also means that EHD deer outbreaks can last until it gets cold and frost eliminates the midge populations.

How To Know If A Deer Has Epizootic Hemorrhagic Disease (EHD)

While EHD can be confused with various similar viruses, there are some clinical signs and symptoms to look out for. Deer will generally start to exhibit symptoms as little as 7 days after they were bit by a midge carrying the disease. The onset is often very sudden.

Clinical Signs & Symptoms Of EHD

Infected animals will often be lethargic, disoriented, and weak. They will lose their appetite along with their fear of humans. Other symptoms include ulcers in the mouth, excessive salivation, rapid pulse, and respiration rate, and fever.

Because of the fever, deer with EHD will often submerge themselves in water to try to cool down and reduce their body temperature.

EHD In Deer or Epizootic Hemorrhagic Disease, symptoms, treatments

Blue Tongue Appearance

Due to reduced blood oxygen levels, a deer suffering from EHD will also generally have a blue tongue. This is also a symptom of the Bluetongue virus – the other hemorrhagic disease that affects deer. Now you can probably tell why it can be difficult to tell the two diseases apart. The clinical signs are very similar.

Epizootic Hemorrhagic Disease can also cause a swollen neck and head. If a deer has the chronic form of it, its hooves may be broken due to growth interruptions. This often causes them to become lame.

Disease Length

Deer may be sick for several weeks, but they can recover. However, with the more severe form of the disease, they can go into shock within 8 to 36 hours of its onset and die.

Acute EHD and peracute EHD are the most serious forms of the virus. If animals have one of these forms, they usually salivate excessively and present with nasal discharge and hemorrhaging of the skin.

While many can die from an EHD deer outbreak (especially northern deer), the survivors will have developed antibodies, which will make them less susceptible or even immune to any future outbreaks.

How To Tell If A Deer Has Had The Disease And Survived

If you’ve spotted some deer or killed one during hunting season and want to know how to tell if they’re survived an EHD infection, have a look at their hooves. Those that have had EHD often have cracks and indentations in their hooves from sloughing and splitting. This is very typical of the chronic form of the disease.

What Can You Do?

If you come across a deer with the symptoms discussed above, or a dead deer lying in or near water, you should alert your nearest wildlife agency. You will need to provide a description and the location of the animal so that the agency can determine the next best steps to take.

EHD Prevention And Control

If you have a property situated close to deer populations, it’s important to take steps to prevent outbreaks from occurring. Here are some of the things you can do to prevent it.

Limit Breeding Sites

A good place to start with EHD prevention is reducing the abundance of midges as much as possible. This means making sure that no water sources and troughs sit stagnant for too long as this will provide the perfect breeding spot for biting midges and gnats.

While you can’t control what happens in lakes and ponds, you can make sure that midges aren’t breeding on your property. To do so, ensure that you stop your troughs from overflowing, fix any leaking pipes, and remove any standing water sources.

Protect Livestock

If you’re worried about your livestock, there are ways that you can limit the midges moving around your stables. One way is to install screens with a very fine mesh to stop midges from flying in. However, this will not completely prevent midges from getting in.

You should also strategically place some fans around the stables. Midges are very, very small. So, wind from a fan substantially decreases the likelihood of midges biting your livestock.

Create Appropriate Watering Holes For Deer

If you’re someone who uses salt licks, deer feeders, and troughs to attract deer, it’s important that you don’t inadvertently place them near a potential midge breeding ground.

Midges like shallow, muddy water to breed in. So, if you construct a deep, clean watering hole with banks of rocky or vegetation, the midge reproduction should be minimal. It’s important to produce a healthy, vegetated wetland for deer to drink from and place them in shady, cool locations so that they won’t get warm in the summertime.

This will help to make sure that your watering holes do not become a midge breeding ground in the dry seasons.

When placing your salt licks or feeders, make sure that you don’t place them near stagnant water. Doing what you can to improve the quality and health of small water sources on your land can help make a big difference to the frequency and severity of EHD deer outbreaks.

In Summary

Epizootic Hemorrhagic Disease (EHD) can be very serious. It can wipe out up to 90% of the whitetails infected with the virus depending on the location. While often confused with similar diseases, it should not be taken lightly. It is very important to take note of the symptoms and keep an eye on your local deer populations.

There are also several things that you can do to prevent EHD deer outbreaks in your area. This will help to keep the deer, as well as nearby livestock safe and healthy.

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