Insect-borne disease kills local deer

by Eric Stearley

In late September, Scott Poole took some time out of his Sunday afternoon to look over a property that he has often hunted in the past. An avid hunter for the last 30 years, Poole inspected the property just over a week before the opening of bow hunting season, which began Oct. 1. As he approached a creek, he found a deer lying motionless, its body half in the water, half out. Further down the creek, he saw another dead deer laying in the water, and then a third, on the bank of the creek. 

Poole says he thought this was strange, but he didn’t think much about it until he found a fourth deer that same week on his own property, less than a mile from where he found the others.

“Anytime I’ve ever found a dead deer, I inspect it and there’s always a bullet hole or it was a car wreck,” said Poole.

These deer were different. Poole explained that they looked perfectly healthy. They didn’t appear to be sick. There were not gunshot wounds or signs of trauma. The only thing he noticed was a blue tongue sticking out of the deer’s mouths. The disease that turned their tongues blue could be more deadly to white-tailed deer than hunters’ rounds and driver’s cars combined.  

“EHD is the most severe disease, from a deer’s perspective, that has the ability to affect deer numbers immediately,” said Indiana DNR Deer Research Biologist Chad Stewart.

EHD stands for Epizootic Hemorrhagic Disease, and it’s a deadly viral disease that can kill a healthy deer very quickly. Symptoms are similar to Blue Tongue Virus, though BTV affects sheep and cows more often than deer and hasn’t been confirmed in Indiana deer populations. Small flies called culicoides spread the virus. Also known as midges or “no-see-ums,” these little biting insects pass the virus to the deer on which they feed. The disease was first discovered in 1955 in New Jersey and Michigan, but has likely been around since the late 1800s, according to the DNR.

Symptoms typically develop within seven days of infection and include extensive hemorrhages, loss of appetite, loss of the fear of humans, growing progressively weaker, excessive salivation, rapid pulse and respiration, ulcers on the tongue, or an eroded dental pad. Infected deer develop a fever, causing them to seek water to cool off. This is often where they die. Blood clots in the lungs result in a lack of oxygen in the blood. This causes the tongue to turn blue. Within 36 hours of symptom onset, the deer enter a shock-like state, become unconscious, and die. 

“Most of the time when you find them near the water, it’s EHD,” said Stewart.

EHD has been confirmed in several counties across the state. The largest outbreaks have been in the southern counties, but unconfirmed reports have come in from Wabash, Miami, Fulton, and Huntington counties. Part of the difficulty in confirming EHD is that a sample must be taken within 24 hours of a deer’s death, which is hard to accomplish when dealing with wild animals. The disease has been confirmed in a captive population of deer in nearby Kosciusko County.

The deer-killing malady has never been confirmed in Wabash County by lab testing, but Stewart said that last year, it was confirmed by hoof inspections. The mortality rate is high, but when a deer does survive EHD, they often have sloughed hooves. This interruption in the growth of the hoof can cause it to fall off completely. By inspecting hooves, the DNR can determine what areas were hit by EHD after the fact.

Dr. Stephen Pilgrim, veterinarian and owner of Countryside Veterinary Hospital, has worked with captive deer affected by the disease. He noted that from his experience, the disease seems to prefer bucks to does, with more males of the species dying. Dr. Pilgrim stressed that deer that survive EHD often have a shorter lifespan due to the sloughed hooves, especially where they fall off completely. This limits mobility.

“They may not grow back,” said Pilgrim. “Long-term, they may starve to death or be taken by predators.” 

In previous years, Dr. Pilgrim has confirmed the disease in pen-raised herds in Kosciusko and Miami counties through lab-tested samples. Last year in Nappanee, one deer raiser lost 90 percent of his herd to EHD. While the disease can be devastating to localized populations, it is very sporadic in nature and may leave a nearby group unaffected. Pilgrim says this allows wild deer population numbers to bounce back.

“The only thing you can predict with EHD is when it will occur,” said Stewart. “You have no idea where it’s going to pop up or how intense it’s going to be.”

EHD outbreaks typically occur in late summer and fall. In 2007, there was a particularly bad outbreak, with the disease reported in 59 counties. Pike county in southern Indiana saw a 40 percent drop off in antler harvest as a result. The story was the same in 2012.

“Last year was the worst outbreak probably in the history of the state,” said Stewart. “Guys were finding a dozen dead deer along a stream bank.”

Stewart believes this was largely due to a new strain of the virus. EHD V-1 and V-2 have been in the state for years. According the Stewart, these are considered “native” strains. Last year, EHD V-6 a “more exotic” strain was confirmed in Indiana.

“Anecdotally, it appears that six is more virulent,” said Stewart.

This year, a dry summer season in much of the state is to blame for the outbreak. Midges breed in the mud flats on the sides of creeks and rivers. Less rain means more exposed mud near water, resulting in an increased population of midges.

Dr. Pilgrim has worked with a private lab to make non-commercial EHD vaccines for the pen-raised animals he has worked with. He says that this, however, does not always prove effective, as the sporadic disease may be gone from a population before the vaccine is ready. He cannot hold onto vaccines from one year to the next due to USDA regulations, so each year, vaccines must be remade using samples from infected deer in hopes that they are ready in time to save the others.

In addition to white-tailed deer, mule deer, and pronghorn antelope, EHD has been found in cattle, sheep, and dogs, though they rarely develop symptoms. The presence of EHD in livestock and deer has raised concerns about meat safety, but won’t likely be an issue.

“Unlike West Nile, EHD is not spread to people,” said Pilgrim. “That’s the good thing.”

The DNR confirms this. EHD can only be spread through insect bite, and even then, does not affect humans. They recommend normal precautions when harvesting deer, including proper cleaning and cooking. Even so, there is lingering apprehension about the safety of the meat. Stewart said that personally, he wouldn’t serve his family meat from an animal that may have been sick, whether the disease can affect humans or not. Poole, owner of a local meat market, agrees.

“I’m not going to eat venison this year,” he said. “There’s no way.”

If there is an upside to this, it’s the cool nights that residents of northern Indiana are beginning to experience as the fall season continues. Midges cannot survive past the first frost, and since EHD is such a rapidly progressing disease, the last deer infected this year will be dead within a couple weeks of that frost.  As soon as it gets cold enough, the deer are safe from epizootic hemorrhagic disease until next year.

Come the first of November, the DNR will once again set up hoof checkpoints. This will give them a clear confirmation of where EHD hit this year in Indiana, and how severe the outbreak was.

For now, Wabash County remains in the “suspected” category when it comes to the 2013 EHD outbreak. For those who have stumbled across the blue-tongued, healthy looking deer dead by the water’s edge, little confirmation is needed. Stewart and Poole urge anyone who finds a dead deer in or near water to report it. The deer hotline number is 812-334-3795.

“I would like for all hunters to step up to the plate,” Poole said about reporting dead deer.

With outbreaks appearing to get worse, better understanding this disease and working to prevent it could prove important to future deer populations.

“It’s going to be here for a while,” said Dr. Pilgrim “I think it’s endemic and will stay here and pop up from time to time."

Posted on 2013 Oct 08