The Triangle of Death: Anthrax Outbreak Hits Southern Deer Herds

By author of Brow Tines and Backstrap

While most hunters are worried about EHD, some are dealing with a much different summertime threat

It’s like a bad dream you never wake up from. That’s how many in South Texas are referring to the latest bout with deer disease. In summertime, for most hunters, that comes in the form of Epizootic Hemorrhagic Disease (EHD). Not for Texans, though. It's anthrax. It kills deer in droves. And most hunters outside of Texas’ not-so-golden triangle have never even heard of it.

Anthrax has been detected in whitetails in Crockett, Edwards, Kinney, Maverick, Sutton, Uvalde and Val Verde Counties. (TPWD photo)

DVM Bob Dittmar, a wildlife veterinarian for the Texas Parks and Wildlife Department, shed some light on the issue.

“Anthrax is a disease that can cause high local mortality in deer,” Dittmar said. “It’s been estimated that some ranches have lost more than 50% of their deer herd in past outbreaks in southwestern Texas. It may take three to six years for those herds to regain numbers.”

For a disease that’s so little known, it’s reportedly been around for hundreds of years. And it packs a big punch that’s hard to dodge.

“Anthrax is caused by a spore-forming bacterium, Bacillus anthracis,” Dittmar said. “The spores are capable of surviving for extremely long periods of time in the soil. These spores like alkaline, calciferous soils which we have in the endemic area of southwestern Texas. Climatic conditions, specifically a wet winter and spring followed by hot, dry weather, appear to allow the spores to surface where they are consumed or inhaled by animals while grazing. Biting insects (flies) may play a role in transferring this disease as well. This year is the perfect storm for anthrax.”

“This year is the perfect storm for anthrax.”

Ever heard of Texas’ golden triangle? This place isn’t it. It’s the triangle of death. Or at least, has been considered as much from time to time throughout history.

“There is a triangular area in southwestern Texas,” Dittmar said. “It’s roughly bounded by a line from Uvalde to Ozona to Eagle Pass. This includes parts of Crockett, Edwards, Kinney, Maverick, Sutton, Uvalde and Val Verde Counties. Though anthrax can and has occurred throughout the state, this area seems to have a confirmed case or two almost every year. Some years many cases. Please understand that many mortalities that might be anthrax are not tested or reported.”

Right now, the spores seem to only be affecting deer in four counties.

“So far, cases have been confirmed by laboratory diagnosis in Crockett, Kinney, Sutton and Uvalde counties,” Dittmar confirmed. “But it’s in multiple species, including whitetails. There have been multiple reports of mortalities attributed to anthrax in whitetails that are not sampled for testing. This year, there are cases in northern Sutton and Crockett counties that are north of the area where it’s mostly occurred in the past.”

As mentioned, deer aren’t the only animals at risk. Other cervids and livestock are prone to infection, too.

“It can affect many species,” Dittmar said. “Grazing animals like cattle, horses, deer, antelope, sheep and goats are very susceptible. Swine can become infected but are less likely to.”

Sadly, there isn’t anything that biologists, hunters, ranchers and land managers can do to prevent anthrax’s death toll in cervids.

“Regrettably, once an anthrax outbreak starts, there is not much wildlife managers can do,” Dittmar said. “Keeping deer and livestock numbers at or below carrying capacity may help keep animals from grazing or browsing close to the ground. I recommend moving feeders or putting material under feeders, so water won’t stand or create a situation where you have a dusty depression when it’s dry. Hopefully someday we will have an oral vaccine suitable for deer.”

Luckily for farmers and ranchers, some preparedness can prevent it from impacting their livestock, though.

“A vaccine is available for livestock, but again, it needs to be given before the epidemic starts,” Dittmar said. “Also, with livestock, it’s possible to move them to other pastures where the disease may not be present.”

With its heavy tolls on deer, other cervids, and livestock, it begs the question, can humans be impacted by this threat? The short answer: yes.

“While humans are pretty resistant to anthrax, the biggest danger is from handling infected carcasses,” Dittmar confirmed. “Folks should not handle carcasses or pick up antler or other carcass remains during the course of an outbreak. But overall, carnivores and humans are pretty resistant.”

According to Dittmar, there’s still a long road ahead. This could be just the beginning, continuing to impact deer for several weeks. Or, it could subside and be less severe. Time will tell.

“Generally, outbreaks subside with the onset of cooler weather,” Dittmar said. “So, by hunting season, it will be gone and the danger of infection to hunters is minimal. However, hunters should use gloves, wash hands and thoroughly clean equipment used for processing. Never consume meat from obviously sick animals and thoroughly cook meat to kill bacteria, including the anthrax organism, to be safe for consumption.”

For those with questions, please contact your local biologists. Or, reach out to Dittmar. As he mentioned, current conditions have created a perfect storm for anthrax. It’s important to educate yourself.

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