There have been several reports of pigeon fever in the region. With this in mind, here are some facts about this condition in horses, including information about recognition, prevention, and treatment.
“Pigeon fever” got its name because the most common form of the disease involves swelling and abscessation of the pectoral region, which resembles a pigeon’s breast. The disease is not caused or carried by birds, but instead is the result of infection with a bacterium called Corynebacterium pseudotuberculosis. This pathogen can also affect other animals, including sheep and cattle, but the syndrome in horses is fairly unique to this species. It is most common in arid climates, but can definitely be found in Missouri and all throughout the United States, and its prevalence is increasing.
There are three forms of pigeon fever. The first is the most classic–the aforementioned abscesses in the chest (and potentially elsewhere on the body). While this can be painful and unsightly, most horses make a full recovery. The abscesses may be lanced and drain to facilitate healing, and the horse may be put on anti-inflammatory medications, but antibiotics are rarely indicated. In a more severe (but thankfully less common) form of pigeon fever, abscesses form internally, potentially including the lungs and abdomen. While initial signs of a problem may be subtle, eventually these horses become very ill, and diagnostic tests (including blood work, ultrasonograhy, and more) may be needed to pinpoint the problem. Internal abscesses can be life-threatening, and require aggressive and prolonged antibiotic therapy to provide a reasonable chance of successful treatment. The final (and rarest) form of pigeon fever is called ulcerative lymphangitis; here, the bacteria travel through the circulatory system and form multiple small, draining abscesses throughout the vessels, usually concentrated on the limbs. Cellulitis (bacterial infection and inflammation under the skin) results, and the horse is febrile and extremely lame. Again, aggressive treatment with antibiotics and anti-inflammatories is indicated.
Currently, there is no equine vaccine for Corynebacterium pseudotuberculosis. The most recent vaccine was pulled from the market due to safety concerns. Therefore, prevention revolves around prompt recognition of the disease, so that affected horses can be isolated and treated.
The bacterium can live for prolonged periods of time in soil. Additionally, flies and insects are a major source of transmission between horses (bugs feed on the pus from draining abscesses, either on the horse or after it drips onto the ground, and then bite another horse, thereby inoculating infectious bacteria). Horses affected by external abscesses should be quarantined, and their living quarters should be thoroughly disinfected before allowing other horses into the area. Abscesses should be drained and flushed by a veterinarian once they mature, as well, as this can help to contain the infectious pus, rather than contaminating the environment. Fly control measures are also important: utilizing such things as fly spray, parasitic wasps, fans, fly tape/traps, and more.
Prompt recognition and treatment of disease provides the best chance of limiting the spread of infection and ensuring the horse makes a full recovery. If you have any questions about pigeon fever, or if you suspect your horse may be affected, please don’t hesitate to give us a call at 636-458-6569.