Seasonal Diseases: Pigeon Fever

Pigeon Fever, also known as Dryland Distemper, is an equine disease most commonly occurring in the Fall.  It is a bacterial infection, and in most cases horses will be fully recovered in a matter of weeks.

Pigeon Fever is caused by a bacteria called corynebacterium pseudotuberculosis.  The bacteria lives in soil, and makes its way into a horse’s system through open skin such as a wound or insect bite.  It is contagious and can be transmitted from horse to horse.  For that reason, proper quarantine procedures and biosecurity practices should be observed.

The first case of Pigeon Fever was reported in 1915 in San Mateo County, California.  Originally this infection was limited to the warmer southwestern states, however within the past 20 years, cases have been reported in over 25 states including Hawaii and Florida.  It has also been documented in Mexico and Canada.

The corynebacterium pseudotuberculosis bacteria’s incubation period is about 3 or 4 weeks.  That means a horse can be infected for up to one month before symptoms appear.  Symptoms can include lethargy, fever, and reluctance to move.  The primary symptom of Pigeon Fever is the appearance of large, deep, external abscesses on the muscles of the breast, abdomen, groin, and udder or sheath.  These abscesses are caused by a toxin the bacteria releases, which causes the immune system to build a thick wall around it to contain the pathogen.

In 8% of cases, internal abscesses will develop as the bacteria gets carried to the organs. In only 1% of cases, abscesses form in the lymph channels of the legs, causing extreme swelling and cellulitis in the lower limbs.

Pigeon Fever is diagnosed through a bacteria culture and lab testing.  Except for those rare cases, treatment involves letting the disease run its course.  It can take weeks, but the abscesses will drain and the wounds will heal.  It is not highly fatal, although the symptoms have a very dramatic look to them.

The bacteria causing Pigeon Fever can live up to 8 months in soil, and up to 2 months in hay or stall bedding.  Flies can transmit the disease, so pest management is essential.