Brain abscesses are a natural cause of death in white-tailed deer in parts of the US and Canada. In the Southeast the percentage of white-tailed deer with brain abscesses ranges from 2% to 9%. Key deer are the smallest subspecies of white-tailed deer, and 10% of adult male Key deer had brain abscesses in one study.
Male white-tailed deer are more likely than females to have brain abscesses, and older males have higher rates than younger males. Bucks tend to injure the skin on their skulls while fighting during mating season. When bacteria such as Trueperella pyogenes or Staphylococcus aureus invade the wound and penetrate the skull, the immune system tries to corral the infection and kill the bacteria. An abscess or pus-filled pocket develops, usually near the antler pedicle or a junction between the bones of the skull. Often a canal or tract of pus connects the point of injury on the skull to the abscess in the brain.
Deer with brain abscesses may exhibit signs that mimic CWD such as circling or incoordination and extreme weight loss. Brain abscesses also may cause irregular antler development. People should avoid eating meat from any deer suspected of being ill.