Starting in the summer of 1998 the Front Range area began to experience the effects of the reemergence of a disease known as Pigeon Breast. The bacteria, Corynebacterium psuedotuberculosis, causes Pigeon Breast, also known as Pigeon Fever, Dryland Distemper, or even Dryland Strangles. In 1998, there had not been a case of this disease reported in Colorado in well over 10 years. Since that time, and especially this summer and fall, we have seen a preponderance of Pigeon Fever cases.
The bacteria responsible for this disease are facultative intracellular organisms. Pigeon Fever may occur on the normal skin and mucous membranes, and its survival in the environment is brief. The most common method of infection is through abrasions, and the most common abrasion and transmission method is thought to be through fly and gnat bites. The bacteria can infect many species including sheep, goats, wild ruminants, and camels. A small number of infections of cattle and humans have been reported. In horses the infection is many times initially found as pectoral abscessation. The other common areas, although not the only sites for finding the infection, include the ventral body (lower portion of the belly and chest), the inguinal (groin) region, the mammary glands on mares, and the scrotum on geldings and stallions.
The infection can also begin on the limbs or travel to the limbs creating lymphangitis, which is inflammation of the lymphatic system. The exudates, or drainage, from these abscesses are most often contagious, but the bacteria will not be infectious unless it gains entry through the skin.
These infections can become quite painful and cause a fever. Most cases require substantial time and nursing care to resolve. The bacteria can create an "onion skin" like shell and "honeycomb" type compartments within the abscess. Proper diagnosis and appropriate therapy, will aid the horse in resolving what can be a long-term infective process.
Fortunately our fly season is coming to an end. With the end of the fly season we expect to see fewer horses affected by this virulent disease.