Pigeon fever uncommon in wetter climates, such as the mid-valley

CORVALLIS — Standing in the sunshine outside her barn, Arabian mare Spring Break seems to be genuinely enjoying the soaking she’s getting as owner Betty Massoni directs water along her flanks from a hot-water hose.

But Spring Break’s “spa treatment,” as Betty and husband Gary Massoni call it, isn’t for pampering — it’s to bring the swollen, infected lumps on her flanks to a head, so that they’ll expel the infection inside.

Spring Break is one of a number of local horses who have contracted pigeon fever, a bacterial infection that causes oozing sores to appear on their bodies, swelling up the chest much like a pigeon’s large breast, hence the name. Her stable mate, Muzetta, had to be put down after contracting the infection.

For years, pigeon fever (Corynebacterium pseudotuberculosis) was thought to be contained to dry climates in places such as Colorado and eastern Oregon. But this year, cases are springing up along the Willamette Valley, including some in Corvallis and Lewisburg.

Dr. Michael Huber, a surgeon and director of the large animal hospital at Oregon State University, said there have been many reports of pigeon fever in Multnomah and Clackamas counties, but not as many in Linn and Benton counties. The hospital has treated several referral patients from across Oregon.

Huber said no one knows exactly what spreads the disease, although researchers say sneezing, coughing and bites from flies all are suspects. Any horses that come into the OSU facility with pigeon fever are isolated from other horses.

Pigeon fever appears to be exclusively a disease of horses, and its symptoms start with fever and swelling. It isn’t infectious, Huber said, until “pus starts flowing.”

The Massonis first noticed Spring Break’s illness seven weeks ago, when sores appeared on her chest and belly. At first, they thought it was an allergic reaction to a fly bite. But it quickly appeared that something more serious was wrong with their 17-year-old horse.

Although veterinarian Dr. Brett Hixson hadn’t seen pigeon fever before in this area, he recognized the symptoms and diagnosed Spring Break. Unfortunately, because antibiotics tend to wall off the infection temporarily, only to emerge again after treatment, the only thing owners can do is to drain the sores, keep them cleaned out — and keep infected horses isolated from other horses.

Hixson said the Oregon Veterinary Medical Association is not yet requiring that vets report cases of pigeon fever, and there’s no statewide tally of cases. Hixson knows of five infected horses at his practice, but he said he sees only a small percentage of the area’s equine patients.

There is reason to be concerned. Although pigeon fever is not usually fatal, it was for Muzetta, the Massonis’ 21-year-old Arabian and their only other horse. Muzetta had to be put down after tests revealed massive internal bacterial infection. Unlike Spring Break, Muzetta’s abscesses were on internal organs rather than on the skin’s surface.

Spring Break is eating well and seems hearty. Betty Massoni believes that’s because her abscesses are external. Betty’s doing everything she can to keep the horse comfortable, including giving her three 20-minute hot water treatments a day. When an abscess needs to be lanced, Massoni calls the vet.

“It’s so frustrating, because we’re accustomed to fixing things,” she said. “I am very concerned about her … I’ve seen what the internal disease can do.”