With summer still over a month away, the Texas Animal Health Commission (TAHC) has broadcast an early warning for “Pigeon Fever,” also called dryland distemper, after a large number of cases were confirmed in horses last year in Texas, Louisiana and Arkansas.

The disease, which can be fatal to equine, causes abscesses and swelling in the horse’s pectoral region (breast muscles) causing a “pigeon-like” appearance, and is caused by the bacteria Corynebacterium pseudotuberculosis.

Often associated with extreme dry conditions and drought, the disease is associated with the hot summer season but can happen any time of year. It is often found in dry areas of the Western United States, but officials say it appears the disease may be on the rise in other parts of the country.

“The Texas Animal Health Commission has no specific authority to regulate pigeon fever, meaning we do not require vets to report cases. But we have noted an upswing in calls and questions about the disease in recent weeks,” says Dr. Holly Poremski, TAHC veterinarian and director of laboratories for the agency.

Poremski says 2011 was a significant year for the disease among Texas horses with 350 cultures testing positive at the Texas Veterinary Medical Diagnostic Laboratory (TVMDL) in College Station. That compares to only 100 cases or less reported each year in Texas between the years 2005-2010.

“When conditions get very dry we suspect that dust may carry the bacteria into open wounds, and we also think it may be spread by flies carrying the bacteria from one infected horse to others,” Poremski added.

Officials in Arkansas and Louisiana are also warning veterinarians to watch for signs of the disease, especially if there is another drought.

Louisiana usually has fewer than three cases per year, but the state veterinary lab confirmed 33 in 2011 and officials say that number may be low because horse owners often treated but did not test horses for the disease to save on expenses. They say the actual number could have been as high as 300 cases.

Arkansas officials say they confirmed a dozen or more cases last year after several years of no confirmed cases. A spokesman for the state veterinarian’s office said most horse owners are unfamiliar with the disease and did not know how to treat it.

According to a TAHC press alert this month, horses affected by pigeon fever can show a variety of signs including fever, weight loss, swelling of the breast muscles or ventral abdomen (belly), and other areas of the body. Abscesses caused by the disease are usually external, and the swelling is visible.

Less commonly, the abscesses form inside the horse’s body where they are more difficult to detect. Treatment of horses with internal abscesses can be difficult, with major complications possible. Prompt veterinary care greatly increases treatment success and reduces complications in any case of pigeon fever. The disease can be fatal to untreated animals.

Animal health officials say there are two types of the disease. One infects sheep and goats but not horses; the other infects horses but not sheep and goats. Both types can infect cattle and humans, though human infections are rare.

In addition to flies that can carry the disease from one animal to another, basic sanitation is also critical. Infected horses should be isolated and abscess drainage should be disposed of properly. The draining material contains large amounts of the bacteria and contaminates the area around the horse, potentially spreading the disease. It is also important to promptly treat any wounds that could become contaminated by flies or dirt.

While veterinarians say vaccines exist for sheep, there is no vaccine for horses.