(Other names: Cranial Abscess Syndrome)
Deer infected with Trueperella pygenes that has swollen eyes with greenish discharge. This is a common bacterium in deer that can cause a brain abscess if it enters the skull.
Photo by Joe Caudell, DNR
Deer with green puss caused by brain abscess from Trueperella pygenes.
Picture: BAS 2
Picture Description: Deer with green puss caused by brain abscess from Trueperella pygenes.
Description
Brain abscess syndrome (BAS) is caused by a bacterial infection in the brain. Trueperella pygenes is a common bacterium that is often found the intestinal tract of deer without causing harm; however, when it enters the respiratory system, it can cause infection (that is sometimes seen as green discharge coming from the eye and or a runny nose), or a more severe respiratory infection that can cause pneumonia. When the bacterium infects the brain, the animal will develop BAS. This disease is present in multiple Canadian provinces and several states across the United States, including Indiana.
Transmission
While Trueperella pygenes is common in all age and sex classes of deer, adult bucks disproportionately develop abscesses in the brain. Since the bacterium is commonly spread through open wounds, and bucks regularly suffer cuts on the head as a result of fighting and/or tree rubbing, they are more often infected. They can also develop a crack in the pedicel, the part of the antler that attaches it to the skull, when they are struck by a vehicle. These events allow the bacterium to enter the brain more readily.
Since Trueperella pygenes inhabits the intestinal tract, the bacterium is also spread through fecal matter. Additionally, flies are known to transmit this bacterium among deer.
Clinical Signs
There are several signs a deer can display when infected with Trueperella pygenes. The first signs of infection include open sores on the legs or the base of the antlers. Additionally, abscesses may appear on the mouth, legs, or lymph nodes. Deer can also develop signs of pneumonia, such as raspy breath, along with lameness. Many infected deer will have eye and nose swelling accompanied by a discharge that is green to yellowish in color. Once BAS develops, the deer may display additional symptoms such as weakness, circling, loss of their fear of humans, and incoordination.
Wildlife Management Implications
Deer infected with BAS can often die as a result of it, and BAS is one of the most common forms of mortality for bucks after the harvest season. While this can be of concern to hunters and other people who like viewing large antlered deer, BAS does not typically lead to significant effects on the deer herd at the state or county level; however, local and private deer managers may still be affected on their individual properties. Therefore, managers who are practicing trophy, quality, and other forms of older-age buck management should factor this disease into their herd management plan. In some cases, managers may see an additional 10% of their remaining bucks (postharvest) die from brain abscesses.
If you encounter a deer that appears to be affected with BAS, or you find the skull of a dead buck that shows the classic pitting in the skull or around the base of the antler, please report it using our online Sick or Dead Wildlife Reporting tool.
Human Health Significance
Trueperella pyogenes is a zoonotic pathogen, meaning it can infect animals (primarily hooved animals) and humans. However, human infections are extremely rare. Always take the proper precautions when handling deer carcasses. Wear gloves and wash your hands well before eating, drinking, or smoking. Avoid eating meat that is in direct contact with lesions or abscesses.
Additional Resources
Baumann, C. D., W. R. Davidson, D. E. Roscoe, and K. Beheler-Amass. 2001. Intracranial abscessation in white-tailed deer of North America. Journal of Wildlife Diseases 37: 661-670.
Belser, E. H., Cohen, B. S., Keeler, S. P., Killmaster, C. H., Bowers, J. W., & Miller, K. V. (2015). Epethelial presence of Trueperella pyogenes predicts site-level presence of cranial abscess disease in white-tailed deer (Odocoileus virginianus). PLoS One, 10(3), e0120028.
Davidson, W. R., V. R. Nettles, L. E. Hayes, E. W. Howerth, and C. E. Couvillion. Epidemiologic features of an intracranial abcessation/suppurative meningoencephalitis complex in white-tailed deer. Journal of Wildlife Diseases 26:460-467.