COLLEGE STATION – Experts are cautioning horse owners to be on the lookout for pigeon fever, a bacterial illness that causes abscesses typically in the pectoral region of horses, but in other anatomical sites as well.

Pigeon fever is an infection caused by the bacterial organism Corynebacterium pseudotuberculosis. It is considered endemic in California and some other western U.S. states.

Dr. Amy Swinford, head of diagnostic bacteriology for the Texas Veterinary Medical Diagnostic Laboratory, said the organism can live for months to years in the soil and it may infect the horse through a wound or broken skin. Flies can serve as mechanical vectors to transmit the organism from the environment to horses.

There is currently no commercial vaccine against the organism.

Cases in Texas submitted to the diagnostic lab increased 1,065 percent from 2005 to 2011, according to the agency’s data.

Swinford said one of her own geldings had pigeon fever, but because he only had tremendous swelling of the sheath region and ventral midline without obvious abscesses, the diagnosis was a bit more complicated than in horses that present “the classic pectoral abscess ‘pigeon breast’ lesions.”

“There are different forms of the disease,” she said. “The external abscess form is the most common, but internal abscesses and a condition called ulcerative lymphangitis, while less common, are generally more serious.”

Swinford said most veterinarians find the most effective method of treatment for the external abscess form is to drain the abscesses rather than treating these horses with antibiotics.

“The more serious forms of the disease require the use of antibiotics, and fortunately the bacterial organism is sensitive to all of the commonly used antibiotics.”

Swinford said recent news reports confirmed the disease has been found in horses as far east as Oklahoma, Arkansas and Florida.

The organism may incubate within the horse for several weeks before symptoms appear.

“Clinical signs may include fever, edema (swelling), lethargy, lameness and depression or weight loss, but these vary from horse to horse, and also depend on the form of disease a horse has. My own horse was not febrile (feverish) and never acted sick,” Swinford said. “This is often true of horses that have only external abscesses.

“External abscesses can become quite large and extend deep into tissue, often accompanied by swelling, and may develop along the chest, midline, groin area and various other sites. Internal abscesses may also develop and can often be very difficult to treat.”

Swinford said horse owners who detect any of these symptoms are advised to contact their veterinarian as soon as possible.

“It’s something that should be diagnosed and treated appropriately,” she said. “Unfortunately there’s currently no way to prevent it, but fly control around stables and other types of horse premises may help.”