Hot Topic – EHD, Six Things Hunters Need to Know, Part 1

By Steve Sorensen

Here’s the Lowdown on Deer Diseases

HIV. COPD. EHD. CWD. Every day we’re bombarded by a blizzard of acronyms. We use many of them for medical terms and government agencies. We can’t possibly remember them all, so we assign them an alphabet soup of letters. Acronyms don’t help – the letters just make them scary. (Take the letters IRS, for example.)

standing water a nursery for insects 448x336

Standing water is a nursery for insects. The margins where water is especially murky and stale are prime incubation areas for the larvae that carry EHD. Any swamp where the water level seldom changes, such as this one, has virtually unlimited edges where water stagnates. (Photo by Steve Sorensen)

Of the four that are listed, the first two kill people. The last two kill deer – and hunters should know something about them.

What is EHD?
EHD is an acronym that stands for the tongue-twister Epizootic Hemorrhagic Disease. Some people call it Blue Tongue Virus, though that’s a similar but slightly different affliction. Both are caused by flying insects that bite – gnats, midges, or no-see-ums. Once bitten, a deer develops symptoms in only a week, which include internal hemorrhage, weakness, high fever, bruising, and shortness of breath. Within 8 to 36 hours of showing symptoms, the animal dies. EHD affects ruminants (animals that chew their cud) – mainly sheep, cattle, goats, buffalo, deer, and antelope.

fresh water not likely to produce EDH 232x448

Areas like this are not likely to produce EDH. As evidenced from the debris at the top of the photo, this area is subject to flooding, and fresh water regularly replaces the standing water.
(Photo by Steve Sorensen)

Chronic Wasting Disease (CWD) is also a deer disease, but we’ll save that one for next time. In some respects, EHD is the less serious of the two. For today, here’s what you need to know about EHD.

  1. What is EHD? EHD (and its cousin, BTV) are caused by viruses, and where they have occurred they have killed many deer. In fact, in a localized area it can devastate a deer population.
  2. How serious is EHD? The good news is that a deer herd always rebounds from EHD. Brian Eyeler, Deer Project Leader of the Maryland Department of Natural Resources, says, “We have had EHD in Maryland for many years. This past year was a heavier outbreak than normal, but nothing that would cause us serious alarm.”
  3. How does EHD get spread? EHD isn’t spread from one deer to another. It’s transmitted by biting insects, so you’ll find it around standing water that provides a nursery for the insect larvae. But the culprit isn’t lots of water – it’s the murky, warm, low-quality water found along the edges of ponds, swamps, and other standing water. The insects infected with the virus lay their eggs there, where the larvae gets nutrients from the low quality water.
  4. If insects cause EHD, does wet weather make it worse? Ironically, EHD is less prevalent when summers are wetter than normal. That’s because more rainfall refreshes stagnant water, keeping the water quality higher and less hospitable to larvae. It’s during droughts that the disease gets a boost because ponds and swamps have marginal edges where shallow waters stagnate until rains replenish them.

    sorensen with healthy green county doe 336x448

    A few years ago a buddy and I went to Greene County, PA where excess antlerless tags were available. A few years earlier the area had been hit hard by EHD, but the herd rebounded and I brought home this healthy doe. (Photo by Steve Sorensen)

  5. When are deer most at risk? When the larvae become winged adults, the females seek meals of blood. They’re especially attracted to deer because like deer, they’re crepuscular – that means the deer and the insects are most active during dawn and dusk. The insects need blood protein for egg production, and when they feed they inject the deer with the virus that causes EHD.  Then they fly off to lay eggs and begin the cycle again.
  6. Can EHD wipe out the deer? This life cycle of the flying, biting insects holds the key to the reason why EHD is a localized disease, why it’s less of a problem at higher elevations, and why it’s less persistent in cold climates. It usually breaks out late in summer, individual deer die, a cold snap kills the insects, and deer populations recover.

Next time we’ll take a look at Chronic Wasting Disease, where it came from, how it’s transmitted, and why it’s a threat.

Click here to read more great articles on deer hunting, by Havalon’s pros.


About Steve Sorensen

steve-sorensen-head-shotOutdoor writer and speaker Steve Sorensen writes an award-winning newspaper column called The Everyday Hunter®, and he has something to do with most of the content on the Havalon Sportsman’s Post. He has also published articles in Deer & Deer Hunting, Outdoor Life, and many other top magazines across the USA. Invite Steve to speak at your next sportsman’s event, and follow him at[hs_action id=”7771″]

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One Response to Hot Topic – EHD, Six Things Hunters Need to Know, Part 1

  1. Pingback: Hot Topic – CWD, Seven Things Hunters Need to Know, Part 2 | Havalon Knives

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