With the exception of a few arid regions in the Southwest, brain abscesses affect white-tailed deer throughout the remainder of their range.
Brain abscesses occur more often in the southeastern and eastern United States, which is thought to be due to the humid environment. It is a seasonal condition that occurs roughly from September through April and is associated with antler velvet shedding, sparring, fighting, antler rubbing and antler casting.
Nearly 90 percent of all documented cases of brain abscesses have been from bucks, especially mature bucks greater than 3.5 years old.
Some researchers have documented that brain abscesses can account for over half of all cases of natural mortality among 4.5-year-old or older bucks. Because brain abscesses are usually fatal, this is a significant non-hunting mortality factor that should be considered in any quality deer management (QDM) program where mature bucks are desired.
Bucks often have injuries to the pedicle (antler base) and skin as a direct result of the antler growing cycle and rutting behavior. These injuries allow bacteria to migrate through the pedicle or skull sutures (cracks) and into the brain.
Any number of bacteria can be responsible for this condition, but Arcanobacterium pyogenes is most commonly found in samples. Once the bacterium enters the brain, a pocket of puss forms and enlarges until the deer dies.
Deer with this condition often walk in circles and appear to be completely unaware of their surroundings. They may even come toward humans when approached. Some go blind. Most will be emaciated. These signs become much more evident as the condition worsens, eventually leading to death for the deer.
If a deer exhibiting this type of behavior is observed during hunting season, it is probably best to dispatch the animal and call your local Wildlife and Freshwater Fisheries Division (WFF) office to have their personnel verify the behavior was caused by a brain abscess.
If this occurs outside of hunting season, or in an area which prohibits hunting, please call WFF for assistance.
Hunters may not notice clinical signs prior to killing an infected animal, but an abscess often is found when the antlers are removed from the skull. This is when the hunter, deer processor, or taxidermist will notice the puss-filled pocket within the brain, which often oozes when opened and has a very pungent "rotting flesh" odor.
A brain abscess should not be cause for alarm about the local deer herd's health since abscesses are limited to individual deer and are not known to be transmissible from deer to deer. The meat from a deer with an abscess is safe to eat.
Brain abscesses in white-tailed deer are nothing new. They have been around throughout history. People only recently became more aware of this condition, as well as a host of other diseases and parasites that affect the wildlife in which they all enjoy.
Chas Moore is a wildlife biologist for the Alabama Division of Wildlife and Freshwater Fisheries.