Pigeon Fever in Horses: Signs, How It Spreads and Oregon's Fall 2026 Cases

Pigeon fever in horses: what just happened in Oregon

Pigeon fever in horses is a bacterial infection that usually shows up as one or more abscesses on the chest or along the belly. On Sept. 23, 2026, the Oregon State Department of Agriculture confirmed it in one horse in Umatilla County, and 12 exposed horses are under quarantine.

The case was reported through the Equine Disease Communication Center (EDCC) and covered the same day by The Horse and Horse&Rider's EDCC Health Watch. Further suspected cases are under investigation.

It isn't the first Oregon report this month. On Sept. 15, The Horse reported that two horses in Deschutes County had tested positive at two facilities, with exposed horses at both.

None of this is unusual for the season. Pigeon fever peaks from late summer through fall, when flies are at their worst, so owners across the West should be watching now.

What is pigeon fever?

Pigeon fever is caused by the bacterium Corynebacterium pseudotuberculosis. Horses get their own strain of it (biovar equi), which is different from the one that causes abscesses in sheep and goats.

The name comes from the swollen chest some horses develop, which looks a bit like a pigeon's puffed-out breast. You'll also hear it called dryland distemper. It is not the same disease as strangles.

It used to be seen mostly in the dry western U.S. The AAEP now notes cases across the U.S. and Canada, with outbreaks in new areas during droughts.

The three forms

Most horses have the external form. The EDCC says internal infection happens in about 8% of cases, which is why a vet check matters even when the problem looks "just" like a lump.

Pigeon fever symptoms to watch for

The classic sign is a firm, often warm swelling on the chest or midline of the belly. It can grow slowly over days to weeks before it comes to a head and drains.

Watch for:

• A new lump or swelling on the chest, belly, sheath or udder, sometimes with patchy hair loss over it
• Swelling along the belly that looks like fluid pooling under the skin
• Fever, dullness or going off feed, though many horses with the external form act fairly normal
• A hot, swollen hind leg with lameness, which can point to the limb form
• Weight loss, colic signs or a horse that just isn't right for weeks, which can point to internal infection

The American College of Veterinary Internal Medicine (ACVIM) puts the incubation period at about three to four weeks. So a horse can pick up the bacteria in late summer and not show a swelling until well into fall.

A swelling on the chest can also be a kick injury, an insect-bite reaction or something else. Only your vet can tell which, often with an ultrasound, a sample from the abscess and a blood test.

Is pigeon fever contagious?

Yes, but not the way a cough spreads. Pigeon fever isn't airborne. The bacteria need a way in, usually a scrape, bug bite or other small break in the skin.

It moves around a barn in a few ways:

• Flies. Horn flies, stable flies and house flies can carry the bacteria from contaminated material to a horse's skin, according to a February 2026 Equine Disease Quarterly review.
• Soil and bedding. The same review says the bacteria can survive up to eight months in soil, and manure helps them last longer.
• Draining abscesses. Pus from an open abscess is full of bacteria and contaminates the ground, stall and anything it touches.
• Shared gear. Buckets, brushes, blankets, tack and tie areas can move it from horse to horse.

That's why the Oregon agriculture department's advice, shared through the EDCC, includes not tying horses in high-traffic areas. A spot where every horse stands is a spot where bacteria build up.

How to prevent pigeon fever

There's currently no licensed pigeon fever vaccine in the U.S., according to the EDCC. Prevention comes down to management, and most of it is simple barn hygiene.

Fly control

• Pick up manure often and keep it away from where horses stand and eat.
• Use fly sheets and fly masks. Ask your vet about repellents that fit your horse.
• Pay attention to the belly midline, where flies love to feed and where abscesses often start.
• Fix drips and wet spots, which help flies breed.

Wound care

• Check your horse daily during grooming, especially the chest, belly and legs.
• Clean and cover small cuts and bug-bite sores as your vet recommends.
• Keep a stocked first aid kit so small wounds get handled the same day.

Biosecurity

• Give each horse its own water bucket, brushes and tack, or clean shared items between horses.
• Don't tie horses where every other horse stands.
• Isolate any horse with a new swelling until your vet has checked it.
• Wear gloves around a draining abscess and wash your hands before touching another horse.
• Follow your vet's advice on cleaning stalls and disposing of bedding from a sick horse.

For more on everyday barn hygiene, see our health basics and care guide.

When to call the vet

Call your vet if you see any new swelling on the chest, belly, sheath or udder, even if your horse is eating and acting normally. Early calls help your vet choose the right approach and keep bacteria from spreading through the barn.

Call right away for:

• A fever, depression or loss of appetite
• A swollen hind leg with lameness
• An abscess that has opened and is draining
• Weight loss, repeated mild colic or a horse that has been "off" for weeks
• Several horses in the same barn with swellings

Don't try to open, squeeze or treat a swelling yourself. Opening an abscess before it's ready or in the wrong way can make things worse and spread bacteria around the barn. How and when to treat it is your vet's call.

What to watch next

Oregon's cases are under official quarantine, and the state agriculture department decides when they're released. Check the EDCC alerts page for any updates on the suspected cases now under investigation.

If you're in the West and hauling to shows, clinics or trail rides this fall:

1. Bring your own buckets, hay bags and grooming kit.
2. Don't let your horse stand where strangers' horses have been tied if you can avoid it.
3. Look over the chest and belly after every trip for the next month.
4. Ask your barn manager how they handle a horse with a new swelling.

Fall is also peak time for other issues. Read up on rain rot and strangles, and browse the latest on our trends page.