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Native vs. Non-Native by Gabriel Karns, M. Colter Chitwood, Chris Moorman, and Dr. Chris DePerno
Oaks For Bucks by Chris Moorman
Seek Professional Help by Jonathan Shaw
Creating Mother Nature’s Food Plot by Dr. Chris Moorman
Deer Dispersal by Dr. Jonathan Shaw
Fat and Healthy by M.Colter Chitwood
Take Nothing For Granted by Stephanie Mallory
Of Habitat and Antlers by Richard A. Lancia
How Accurate Are We? by Gabriel Karns, M. Colter Chitwood
To Cull or Not to Cull? by Richard A. Lancia, Mark C. Conner
Water Query by Realtree Whitetail Team
What's In An Antler? by Team Realtree
Pokeweed Problems? by Team Realtree
Attraction Without Plots by Team Realtree
"Pressured" Movement by Team Realtree
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Quality Deer
Management Association
Whitetail Insider
Brain Abscess in White-Tailed Deer
Before spring green-up can hide this past year’s fallen deer antlers, thousands of people will invade the late winter woods in search of shed antler treasures. Not only do shed hunters pick up antlers, they also stumble across un-retrieved hunter harvests and deer that died of natural causes. You might be inclined to blame a dead deer on vehicle collision or outbreaks of epizootic hemorrhagic disease (EHD), but you may find clues that suggest otherwise. In the same vein, sheds might also clue you in that brain abscess is present in your deer population.
Brain abscess (also known as intracranial abscessation) is a source of natural mortality in white-tailed deer populations across portions of the United States and Canada. Occurring primarily between October and April, cases of brain abscess are believed to be directly related to breeding activities (i.e., antler sparring, rubbing, or antler casting). Through subcutaneous cuts and injuries to the antler pedicles or skull, Arcanobacterium pyogenes (an infectious bacterial organism) penetrates the cranium through the sutures (cracks) of the skull or directly through an injured antler pedicle. Once inside the brain cavity, the bacterium proliferates and forms an abscess that consists of a 1-3-cm lump of odiferous pus. Deer with brain abscess may exhibit symptoms such as incoordination, fearlessness, weakness, blindness, and emaciation. The symptoms are usually followed by death, although infected deer may be predisposed to predation or vehicle collision because of their weakened, delirious state.
In a survey of deer mortality reports from the Southeastern Cooperative Wildlife Disease Study (SCWDS), brain abscess accounted for 2.2% of overall deer natural mortality, 4.9% of buck natural mortality, and 9.3% of adult ( > 2.5) buck natural mortality. Interestingly, they also found that brain abscess is extremely rare in the more arid regions of Texas and southern Oklahoma. In our research project through North Carolina State University, we monitored 33 bucks 2.5 years or older with GPS radiocollars at Chesapeake Farms on the Eastern Shore of Maryland. Because radiocollars were equipped with mortality sensors, we were able to retrieve 26 of the deer shortly after death and determined that eight (31%) of the 26 deer had at least one brain abscess. An alarming fact was that seven (54%) of the thirteen older “trophy” bucks (4.5 years or older) in the study had brain abscess.
If you find a deer that has not yet decomposed, you can open the brain case (exactly how you would saw the antlers off a buck) and look for a marble- to golf ball-sized lump of pus. Be careful to use latex gloves and standard care to avoid coming in contact with the infected material. There may even be pus leaking out from around an antler pedicle or through the eye socket. If the deer has decomposed, examine the skull sutures between the antlers and the antler pedicles. Signs of brain abscess may be evident as pits or holes on the outside or inside of the skull. The sutures or antler pedicles may also exhibit a ‘melted’ or eroded appearance. Detecting these symptoms alone or in combination probably indicate that you have found a brain abscess casualty.
If you are an avid shed hunter, you know that every antler is special and unique from the coloration of the tips of the tines to the beading around the antler base. The actual antler base (where the antler was attached to the pedicle) is no different. Interestingly, you can even use the characteristics of the detached antler base as an indicator of brain abscess risk. Most antler bases appear to have cleanly separated from the buck’s pedicle during shedding; in fact, most people have never seen anything different. However, antlers sometimes shed with portions of the pedicle or skull still attached. ‘Deep’ sheds could be due to a traumatic injury sustained during fighting or from a non-fatal vehicle collision. The other possibility is that the abscess-inducing bacteria has compromised the bone’s strength and resulted in an irregularly shed antler. At Chesapeake Farms, approximately one in four shed antlers have extra bone material attached to the base. If sheds are picked up shortly after being dropped by a buck, antler bases may even smell rotten and have a gangrenous appearance. These bucks are probably subject to a much higher rate of brain abscess, if they are even still alive. We believe the relatively high percentage of ‘deep’ sheds at our Maryland site is directly related to the site’s high rate of brain abscess among adult bucks. Additionally, it seems that bucks with antler irregularities close to the pedicle were at a higher risk of brain abscess in our study.
Why is brain abscess extraordinarily prevalent at our Maryland site but seemingly non-existent at other locations? Because Chesapeake Farms has been under quality deer management (QDM) for over a decade, the increased male age structure may elevate breeding competition and predispose individuals to disproportionately more injuries than would occur in traditionally-managed populations. Also, high deer density on the Eastern Shore could be a factor that increases stress and injuries during breeding season, possibly leading to increased brain abscess rates. Environmental conditions may also contribute to increased brain abscess, such as high humidity, abnormally large tick infestations, and mild climate.
In populations that have similar environmental and herd demographic characteristics of our Maryland site, land managers and hunters should be aware of brain abscess and its potential impact on the deer herd. Although Chesapeake Farms’ QDM program has been extremely successful and produced some truly monster bucks, it is discouraging to know that a significant percentage of trophy bucks are succumbing to brain abscess. Now that you know how to identify brain abscess casualties, you can survey the deer herd where you hunt and determine whether or not brain abscess is a local natural mortality factor. If you do find evidence of brain abscess, we would like to hear from you in an email (Email to grkarns@ncsu.edu) about your findings as we are continuing to look at the disease and its distribution across the country.
By Gabriel Karns – M. S. candidate in the wildlife sciences program at North Carolina State University, Department of Forestry and Environmental Resources
Co-authors: Richard A. Lancia –Fisheries and Wildlife Sciences Program, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695 USA; Christopher S. DePerno – Fisheries and Wildlife Sciences Program, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695 USA; Mark C. Conner – DuPont Crop Protection, Chesapeake Farms, Chestertown, MD 21620