Introduction/Causative Agent: Pigeon fever is the common name for infections caused by the bacterium Corynebacterium pseudotuberculosis. This problem is also called pigeon breast, Colorado strangles, and dryland distemper in some areas.
Clinical Signs: When a horse becomes infected with Corynebacterium pseudotuberculosis, the bacteria often infect the muscles causing abscesses to form. These abscesses often occur within the tissues under the chest, armpits (axillary regions), between the hind legs (inguinal areas), under the abdomen, and down the legs. As the disease develops, the horse will often have draining abscesses. A few horses may act sick, have a fever, suffer weight loss, go off feed, and even abort when pregnant. Depending on the size and location of an abscess, some infected animals may have gate abnormalities and lameness. Occasionally, these abscesses form internally. Most horses return to normal about 3 weeks after having the abscesses rupture or lanced. In a small percentage of horses, the abscesses return and then resolve and then may return again, over and over. These horses are ones that often get treated with antibiotics but may never be cleared of the infection.
Disease Transmission: A horse gets this disease when bacteria enter through the skin or mucous membranes and then enter the lymphatic system. Breaks in the skin on the legs or breaks in the gums of the mouth give areas for the bacteria to enter the body. The bacteria are found in the soil and can survive for extended periods of time even when exposed to direct sunlight.
Treatment: The external abscesses are treated by draining the abscess. Most abscess are drained by lancing the bottom most area of the abscess with a surgical blade. The abscess material is completely removed, and the abscess is flushed with dilute betadine on a daily basis. The opening into the abscess is kept open by removing any blood clots or scabs that form in the first few days and by repeated flushing. The opening into the abscess should also be protected from flies by using a fly repellent. If the horse is not sick, antibiotics are not usually given. It is thought that administering antibiotics in these cases may actually hinder the development of the abscesses and prolong the duration of the infection. If it is determined that the horse has internal abscesses, antibiotics, such as penicillin, are often given.
Prevention: To help prevent the spread of the disease, all infected horses should be isolated and strict sanitation must be observed when handling the horse. Particular care should be used when lancing an abscess or when drainage from an abscess is present. Laytex gloves should be worn and then disposed of before moving to another animal. Hands, gloves and equipment can easily spread the infection. Flying insects can also spread the disease (by getting the bacteria on them and moving to the next animal), so it is essential to keep the horse isolated.