Pigeon fever is a disease of horses caused by the gram positive bacterium Corynebacterium pseudo-tuberculosis. It's also known by pigeon breast and dryland distemper. The swollen breast, which is often seen, may be where the name originated, but it has nothing to do with pigeons.
The most common form of the disease is the development of large abscesses in the pectoral region or lower part of the abdomen, girth and inguinal area. These abscesses may cause 3- or 4-inch thick swellings that can cover most of the lower body. This is called the external form of the disease.
Rarely, abscesses may develop deep in the muscles, especially the triceps or axillary area or the stifle. These abscesses may not be visible, but can cause extreme lameness. More rarely, joint and bone abscesses may occur, which are life threatening. In California and Texas, some cases of internal abscesses have been diagnosed, which can be very difficult to treat.
Abortions have been associated with pigeon fever in areas where the disease is endemic. Ulcerative lymphangitis of the hind legs can be caused by Corynebacterium pseudo-tuberculosis, where the hind legs become swollen with areas of nodules that drain, and treatment is often long and drawn out, with variable results.
The disease is known worldwide. The method of transmission is not known, but some believe the bacteria enters the body through small skin abrasions. It is also believed that insects, such as stable and house flies, may transmit the bacteria. September through December are the months when cases most often occur.
Treatment mostly consists of cleaning the abscesses after they rupture or are lanced. Antibiotic treatment prior to the abscess drainage may slow the development or cause an apparent cure, but the disease may recur when antibiotics are discontinued.
Laboratory culture of the bacterium will confirm the diagnosis, but the diagnosis of the external form is often made easily by the clinical signs. Ultrasound may show abscesses and synergistic hemolysis inhibition titers can be done by drawing blood.
There is no vaccine. Prevention probably can be helped by fly control. Some people claim that cattle are often in the vicinity.
Dr. John Harris is a longtime area veterinarian.