Q: I have heard some horse friends in Texas talking about “Pigeon Fever”. What is it and do we need to be concerned about our horses in the Mid-south getting it?
A: Pigeon Fever is caused by the bacterium Corynebacterium pseudotuberculosis. It is found in the soil and thrives in dry, dusty environments (such as the Western United States), and is spread from horse to horse by flies.
The vast majority of the time, horses infected with Corynebacterium develop large, painful abscesses under the skin that resolve within a week or so, and they have no long-term or life threatening health effects. The most common location for the abscesses are the pectoral muscles (hence the name Pigeon Fever) or near the sheath or mammary glands. There is usually a significant amount of edema associated with the abscess, and some horses will have fever and a poor appetite for a few days. If the abscess is on or near a limb, they will often be lame due to the pressure of the building abscess, and improve significantly once the abscess ruptures. Veterinarians treat these abscesses with warm compresses or poulticing agents to encourage them to rupture more quickly. Once the abscess is near the surface of the skin, it can usually be lanced to speed draining and healing. Some cases but not all will require antibiotics and NSAIDs such as Bute or Banamine.
In a small number of cases, Corynebacterium can cause internal abscesses in the chest or abdomen that require more intense treatment and can be life threatening. Horses with an internal abscess often have vague signs and can require a bit of sleuthing on the part of your veterinarian to make a diagnosis. Clinical signs may include gradual weight loss, dull demeanor, and intermittent fevers. Horses with abscesses in their chest may have a cough or nasal discharge. The abscess is usually diagnosed by a combination of ultrasound, radiographs, and rectal palpation. Treatment consists of long term antibiotics and using bloodwork or imaging to monitor progress.
There have been several cases of Pigeon Fever in Mississippi and Tennessee over the last few years, but fortunately we have not experienced the massive “outbreaks” that the Western US has in the past. During these outbreaks, it would not be uncommon for most of the horses in a barn to get Pigeon Fever over the course of a few months, despite everyone’s best efforts to control flies and isolate infected horses. The good news is that this disease is mostly an inconvenience for horses and owners, and rarely causes life threatening problems.
Since fly season is approaching, we may start to see some cases of Pigeon Fever in the Mid-south. We encourage horse owners to use good fly control practices and clean any small wounds their horse gets with a disinfectant such as chlorhexidine or betadine. If you notice a swelling or sore area, especially on your horse’s chest or belly, call your veterinarian to discuss it!