EHD Deer Disease Outbreak Escalates: Is Your Local Wildlife at Risk?

Deer such as white-tailed deer and mule deer are susceptible to the viral diseases known as epizootic hemorrhagic disease (EHD). It is transmitted by biting midges, often known as no-see-ums or punkies (Culicoides spp.).

EHD outbreaks often worsen as summer transitions into the fall season, which raises questions about the health of the surrounding animals. In the late summer and beginning of the fall season, when biting midges are most active, EHD epidemics are most frequent. Although outbreaks may happen anywhere in the country, the southern and midwestern states experience them the most often. This page will provide you a thorough understanding of EHD and the dangers it presents to the deer populations in your region.

Key Takeaways – Is Your Local Deer Herd at Risk?

The important findings relating EHD and the deer population in your area are as follows:

  • As fall approaches and midge activity rises, EHD risk is at its maximum.
  • When EHD epidemics occur often, the effects are worse in the northern states.
  • Because local deer populations are not immune, EHD may wreak havoc.
  • An accurate diagnosis is necessary to prove that EHD is the cause of deer fatalities.
  • Fall weather that is cooler will interrupt the EHD transmission cycle.  
  • Long-term impacts on deer populations tend to be limited

What is EHD and What Causes It?

A virus from the orbivirus family that affects white-tailed deer is the source of EHD. EHD virus 1 (EHDV-1) and EHD virus 2 (EHDV-2) are the two strains of the EHD virus that may infect deer. These EHD strains have a strong connection to the sheep-affecting bluetongue virus.

EHD is transmitted by biting midges, which are little insects sometimes known as “no-see-ums.” The EHD virus enters a deer’s circulation when it is bitten by an infected midge. When midges bite deer that are already carrying the virus, they get EHD and become sick.

Only midge bites may transmit the EHD virus from one deer to another. Additionally, EHD cannot infect humans; it exclusively affects ruminants like cattle, sheep, and deer.

Common Symptoms of EHD in Deer

Early SymptomsAdvanced Symptoms
Sluggish behaviorLack of fear of humans
Enlarged headReduced appetite
Swollen neckSeeking water sources
Swollen tongueRespiratory difficulties
Swollen eyelidsWeakness

EHD Outbreak Durations and Influencing Factors

Epidemic DurationFactors Influencing Duration
4-8 weeksSeasonal midge activity and first frost
VariedImpact of late frosts on outbreak duration
Availability of midge populations

Regional Susceptibility to EHD Outbreaks

Most Affected RegionsRegions with Limited EHD Occurrence
Southern and Midwestern United StatesNorthern United States and Canada
States around mid-Atlantic and Gulf coastsRegions with milder temperatures
Areas with prolonged warm seasons due to climate changeAreas with poor midge habitat

When Do EHD Outbreaks Occur?

In late August and September, these small midges thrive in the warm and humid climate and play a major role in nature’s drama. The deadly Epizootic Hemorrhagic Disease (EHD) breeds at this seasonal meeting, using peak midge activity to destroy unwary deer herds.

The first hard frost will kill out the vector midges when the temperature cools in the fall, completely terminating the EHD transmission cycle. As a result, midge activity is a seasonal factor that influences EHD epidemics.

However, as a result of rising temperatures and prolonged warm seasons brought on by climate change, midge populations are becoming more active for longer periods of time, which might cause EHD outbreaks to continue into the fall.

Which Regions are Most At Risk for EHD Outbreaks?

Wherever midges are active and may spread the virus to susceptible deer, such as in most of the eastern, midwestern, and southern United States, EHD epidemics happen intermittently. EHD activity has been more persistent in locations around the mid-Atlantic and Gulf coasts, and deer in these areas have built up some immunity, thus outbreaks tend to be milder.

EHD outbreaks are substantially less common in northern areas with milder temperatures. Because of this, deer in the northern United States and Canada have little to no immunity, enabling EHD to cause far more damage when outbreaks occur. When EHD epidemics occur in years with warmer temperatures, areas like upstate New York, Pennsylvania, Michigan, and Wisconsin have all had significant effects.

Therefore, because deer have no immunity to the virus, northern areas with poor midge habitat are most at risk for severe EHD outbreaks that may wipe out local deer populations. Ongoing climate change, however, could enable midges and EHD to spread farther north, leading to more frequent outbreaks.

How Does EHD Impact Deer?

The EHD virus incubates in a deer following a midge bite for 4–7 days before the animal starts to exhibit symptoms. EHD destroys the blood vessel lining all throughout the deer’s body, which results in significant bleeding and a high temperature.

Swollen tongues, eyelids, necks, and heads are common in infected deer. They become really frail and have respiratory issues. As EHD worsens, deer lose both their hunger and dread of people. The majority of EHD-infected deer pass away 8 to 36 hours after showing symptoms.

Due to the fever brought on by EHD, sick deer often seek out water sources like ponds, rivers, or streams to drink. Deer killed by EHD in herds are typically discovered close to water.

The EHD virus may also lead to a chronic version of the illness, where deer survive the first infection but continue to suffer oral and hoof problems that make it difficult for them to move, feed, and withstand the challenges of the winter.

Even while southern deer with some developed immunity have improved survival chances, EHD nevertheless kills 80–90% of infected deer overall. EHD outbreaks are more deadly in the north because deer have hardly ever been exposed to it.

How are EHD Outbreaks Monitored and Diagnosed? 

State wildlife authorities keep track of and test deer deaths during outbreaks to determine the effect EHD will have on the herd. By reporting sightings of sick or dead deer, the public may assist with monitoring. For recording the effects of EHD, trail cameras have become an effective instrument.

Tissue and blood samples from deceased deer must be examined in veterinary laboratories in order to identify EHD. Viral DNA must be found using polymerase chain reaction (PCR) testing or other techniques in order to make a diagnosis. Necropsies also show the typical lesions and hemorrhages brought on by EHD. To separate EHD from other dangerous disorders like chronic wasting disease (CWD), a proper diagnosis is necessary.

EHD Vaccine

There is no vaccine for EHD, and there is no specific treatment for infected deer. Keeping deer away from biting midges is the greatest strategy to stop EHD in a herd. Providing deer with access to shaded places and cutting tall grass and brush from surrounding deer habitat helps accomplish this.

Can Anything be Done to Control EHD?

Unfortunately, after midge activity has propagated the virus throughout the landscape, there are no practical ways to stop or restrict EHD epidemics. EHD will continue until the vector midges are no longer a factor due to cooler fall weather.

Research indicates that EHD does not have substantial long-term effects on regional deer numbers, despite the fact that it may decimate local deer populations by killing the majority of affected animals. Fawns born during an epidemic don’t become sick and replenish herds.

To promote EHD monitoring and research, hunters may assist with the collection of tissue samples from killed deer. Otherwise, reporting sightings and waiting for the first significant frost are your best bets. Deer afflicted with EHD cannot be treated or given immunizations.

How Can You Keep Tabs on EHD Activity in Your Area?

Here are some pointers for keeping track of the EHD situation in your area as fall approaches:

  • For information on verified EHD detections and outbreaks, visit the webpage of your state’s wildlife agency.
  • If deer fatalities linked to EHD start to increase, keep an eye out for public warnings.
  • For unofficial updates, follow state wildlife disease experts on social media.
  • Discuss field observations with other hunters, landowners, and outdoor lovers.
  • Keep an eye out for news coverage if EHD begins having a significant local effect.
  • Look for public reports of ill or dead deer using the state’s disease reporting tools 

Watching these observation sources might provide you important information about EHD activity before it can manifest itself in your hunting region or garden.


This fall, keep a careful eye on EHD status updates and be ready for the virus to possibly affect your neighborhood’s herd of deer. While EHD outbreaks are short-lived, they may swiftly kill deer populations in places that had never been exposed. If you believe EHD may be present in your hunting region, contact your state wildlife department. The deer population will resurge with the fawns of the next year with the right safeguards and monitoring.

In conclusion, EHD is a seasonal hazard that, under the correct circumstances, poses a serious risk to nearby herds of white-tailed deer. But awareness and alertness will enable you to predict when and when EHD may spread across your deer forests.

Frequently Asked Questions

What early symptoms of EHD are seen in deer populations?

Deer may seem sluggish and have enlarged head, neck, tongue, and eyelids in the early stages of an EHD epidemic. As EHD advances, deer lose both their fear of people and their hunger. Deer that are ill and have fevers may seek for water to drink, thus you may also locate dead deer close to water sources like ponds and streams. Any time you see a deer that’s impaired, contact your state wildlife department.

How long do EHD outbreaks typically last?

Midge activity reaches its peak in the late summer and early fall, and this coincides with EHD epidemics. The epidemic normally stops when the first severe frost arrives because it kills the midges that spread EHD. So, from the time of early identification to the first frost, most EHD epidemics endure 4 to 8 weeks. In certain years, mild late frosts could make breakouts last longer.

Without midges, can EHD pass from deer to deer?

EHD cannot be transmitted from one deer to another by direct touch or any other method. The only vector that may spread EHD via bites is a midge. To catch the virus, a deer must be bitten by an infected midge. The virus cannot infect fresh deer hosts without midges.

Is it safe to handle or process deer that may have died from EHD?

Yes, as the EHD virus can not survive in dead deer, there is no danger of infection while handling or dressing deer corpses. Hunters should use adequate safety precautions including gloves while preparing wildlife. Any potential germs will also be eliminated by thorough cooking.

How long does it take for deer herds to recover from an EHD outbreak?

Most deer populations may recover after an EHD epidemic, according to research, in 2 to 5 years. Deer without prior exposure to or immunity to EHD are introduced into the community by fawns born after an epidemic. EHD epidemics often have a more significant local effect than they do on overall regional deer populations.

James Ellis

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