Pigeon fever is an equine disease that doesn’t have anything to do with pigeons. It’s an infection caused by the bacterium Corynebacterium pseudotuberculosis which results in the formation of abscesses, usually along the chest (pectoral region) and lowest part of the abdomen. The name "pigeon fever" comes from the swelling in the chest region that vaguely resembles a pigeon-breast. A recent report describes and outbreak of pigeon fever involving at least 30 horses in Louisiana, bringing the estimated number of cases in the state in 2011 to over 100.
Pigeon fever is a regionally (and to a lesser degree seasonally) variable disease. It predominantly occurs in California, but over recent years it has expanded its range in the western US, and from this report, it’s obvious that it has a good foothold in some other areas in the south east as well.
Corynebacterium pseudotuberculosis lives in the soil, and causes infections in horses when it gets inoculated under the skin via wounds and perhaps sometimes through fly bites. Once it gets into the tissues, it starts to grow and causes painful (and potentially large) abscesses that often need to be surgically incised in order to drain them.
Infection control practices on farms can help reduce transmission of the bacterium between horses and to reduce the risk of injuries. These include:
- Quarantine of new arrivals and careful inspection for sign of infection.
- Isolation of known infected horses.
- Use of "contact precautions" when dealing with infected horses to prevent transmission of the bacterium via peoples’ bodies or clothing. This involves the use of protective outwear (e.g. coveralls and boots that are only used for the infected horse(s)) and gloves.
- Proper use of handwashing / hand sanitizer by people handling infected horses (or any horses, really, from a broader standpoint).
- Prevention of cross-use of items like buckets between infected/quarantined horses and the general horse population.
- Use of fly repellent, especially on horses with open wounds or draining abscesses.
- Careful cleaning and disinfection of areas potentially contaminated by pus from draining abscesses.
- Inspection of stalls, paddocks and fields for things that could cause wounds that might subsequently become infected.
Pigeon fever is a good example of why it’s important to know disease patterns in your region (and those to where your horses travel). Being aware of the possibility of a specific disease is an important step in diagnosis, and knowing there is disease activity in any area in which your horse may have been is a key part of that. This disease is also an example of why we need ongoing disease surveillance and reporting, because if a disease makes it into new regions, veterinarians and horse owners need to know about that as soon as possible to allow for quicker diagnosis and use of control measures. Unfortunately, organized disease surveillance and communication is sorely lacking in horses.
Photo: A Jiennense Pouter Pigeon, which has a very pronounced breast compared to other breeds. The swelling of a horse’s pectoral region due to abscesses caused by C. pseudotuberculosis is the reason the disease is sometimes called "pigeon fever." (click image for source)