Warning over rise in pigeon fever in horses

Horses with pigeon fever.
Horses with pigeon fever. © Dr JD Fox, Tri-State Large Animal Hospital, Cheyenne, Wyoming

Pigeon fever is on the rise and horse owners are urged to be on the lookout for the distressing bacterial infection.

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

Infection results in abscesses typically in the pectoral region of horses, but in other sites as well.

Dr Amy Swinford, head of diagnostic bacteriology for the Texas Veterinary Medical Diagnostic Laboratory at Texas A&M University, 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 transmit the organism from the environment to horses.

There is no commercial vaccine.

Cases in Texas submitted to the diagnostic lab increased 1065 per cent from 2005 to 2011, the agency’s figures show.

Swinford said one of her own geldings had pigeon fever, but because he only had swelling of the sheath region and ventral midline without obvious abscesses, the diagnosis was  more complicated than in horses that present the classic pectoral abscess 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, swelling, lethargy, lameness and depression or weight loss, but may vary from horse to horse.

“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.”


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