Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose

Brucellosis, Poll Evil, Fistulous Withers

Synonyms: Bang's Disease, Brucella Abortus, Contagious or Infectious Abortion, Enzoonotic or Epizootic Abortion, Supraspinatus Bursitis, Undulant Fever


A fistula is a draining wound from a normally closed structure, through the skin. The classic fistulous withers is an infection of the bursa overlying the spines of the withers by Brucella bacteria. It is usually seen in areas where cattle brucellosis exists.

Infection in horses probably occurs from ingestion of the bacteria shed by cattle. Drainage and swelling of this area are the main signs of this disease. However, wounds and trauma to this area can also result in similar signs. This disease is rarely associated with abortion in mares.

Whenever there is infection, swelling, or drainage in the poll area, it is important to rule out the presence of Brucella. This is done with a culture and determination of Brucella antibody titer. A negative culture does not necessarily rule out the presence of Brucella, as it can be a difficult organism to culture.

Brucellosis is a zoonotic disease, meaning that it can be transferred from an infected horse to humans by inhalation of the bacteria. If you have been exposed to a horse with (or suspected of having) brucellosis you should contact your doctor.

Brucellosis is a reportable disease in some states, meaning that if a horse has or is suspected of having this disease, vets are required to report it to agricultural authorities (usually the State Veterinarian). These authorities may investigate the case as part of a larger effort to monitor equine health and coordinate with other states and the USDA APHIS in preventing the spread of illness or disease on a national and international level.

my vet's role


Guarded to Poor. These infections tend to recur. It may require radical surgery (removal of infected bone and bursa), long term antibiotics, and long healing time.

further reading & resources

Author: Doug Thal DVM Dipl. ABVP