Strangles in Horses: Symptoms, Quarantine and the Fall 2026 Boarding-Barn Outbreaks

Strangles in horses: what's happening this fall

Update (2026-11-03): October alerts added strangles cases in Ontario, Canada, and Oregon, more in Florida and Wisconsin, and a documented end to an Oregon quarantine. Strangles in horses is a highly contagious bacterial infection of the upper airway and the lymph nodes around the throat, caused by Streptococcus equi subspecies equi.

It usually starts with a fever, then thick nasal discharge and hot, swollen glands under the jaw. It spreads through shared water, buckets, tack and people's hands.

This fall it has kept turning up where many horses live: boarding barns. Alerts from the Equine Disease Communication Center (EDCC), many republished by The Horse and EQUUS, have reported cases in six US states since September, and Ontario's agriculture ministry reported three more in Canada in late October.

October 2026 alerts

A foal, a fair and a 10-day gap

The Wellington County colt went to a fair about 10 days before his lymph nodes swelled. The alert says he may have been exposed there or back at his home farm afterward, so the fair isn't proven as the source.

Still, that gap fits strangles' 3- to 14-day incubation. It's exactly why vets advise keeping a horse apart from the herd and taking its temperature for 2 to 3 weeks after fairs, shows, sales and clinics.

What the end of a quarantine looks like

Oregon offers a real example. A Douglas County horse tested positive Sept. 17, 7 horses were exposed, and the state released the quarantine Oct. 19, about a month later. The alert doesn't say what testing was done; release depends on the vet's and officials' judgment, not a set number of days.

September 2026 alerts

None of this means strangles is new or unusually deadly: it's one of the most common infectious diseases of horses worldwide, and most horses recover. What stands out is the setting, barns where dozens of horses from different owners share aisles, water and people. The King County outbreak had been running since June when it was reported, and the biosecurity basics below apply wherever your horse lives.

Strangles symptoms: what to look for first

The first sign is usually a fever, often 103–106°F (39.4–41.1°C), which appears 3 to 14 days after exposure. Within a day or two of that fever spike, the classic signs follow:

• Thick nasal discharge, often yellow-green, from one or both nostrils
• Swollen, hot, painful lymph nodes between and under the jawbones, which may form abscesses that burst and drain
• Dullness and going off feed, because the throat hurts
• A soft cough, often while eating
• Trouble swallowing
• Noisy breathing with the head and neck stretched out, a sign that swollen nodes behind the throat are squeezing the airway (this is an emergency)

That airway squeeze is where the name comes from: badly swollen glands can nearly "strangle" a horse.

Mild cases are the sneaky ones

Horses between 1 and 5 years old usually get the worst of it. Older horses with some immunity, and vaccinated horses, may show only a mild fever, a cough and a runny nose, yet they can still spread it.

September's alerts included a 26-year-old gelding in Kansas and a 30-year-old gelding in Wisconsin, and October's a 17-year-old in Wisconsin, so don't write off a snotty senior as "just a cold."

When complications happen

Most horses recover in about three to four weeks with supportive care. Some develop complications:

• Guttural pouch infection: pus collects in the air sacs behind the throat and can turn a horse into a long-term carrier.
• "Bastard strangles": abscesses in lymph nodes elsewhere in the body, such as the belly or chest.
• Purpura hemorrhagica: an immune reaction that causes swelling of the legs and head and tiny bleeds on the gums.

Deaths are rare, but they can happen with airway blockage or severe complications.

How strangles spreads (and why boarding barns are hot spots)

S. equi is adapted to horses, donkeys and mules (human infections are rare), and it moves two ways. Directly, through nose-to-nose contact over stall doors, fences and shared turnout. Indirectly, on anything that touches a sick horse's nose or pus, which the American Association of Equine Practitioners (AAEP) says includes:

• Water troughs, buckets and hoses
• Grooming tools, tack and blankets
• Twitches and veterinary equipment
• Handlers, including their hands, clothes and boots

Flies can also carry the bacteria. It dies within a day or two on dry surfaces, but AAEP notes it can survive up to 34 days on wet surfaces in cold weather, so fall and winter mud matters.

The horses you can't see coming

The trickiest spreaders look healthy. Horses start shedding bacteria from the nose 2 to 3 days after the fever begins, and horses still incubating the disease can pass it on before they show signs.

Recovered horses usually keep shedding for several weeks: AAEP says typically 2 to 3, Merck about 4 to 6. A small number hide bacteria in their guttural pouches and shed on and off for months; the Merck Veterinary Manual cites up to 18 months.

New arrivals are the classic way in. On Sept. 9, Washington officials reported a Whatcom County horse that tested positive after being bought in Texas and shipped north; two exposed horses on that farm went into quarantine.

Strangles quarantine: how long does it really last?

There's no fixed length. If you add up the timelines in veterinary guidelines, a barn with an outbreak is often restricted for six to eight weeks or more after its last new case, and outbreaks that keep producing cases can run for months. The clock is set by the last horse to get sick, not the first, and every new case resets it.

A single case that doesn't spread can clear sooner: Oregon's Douglas County quarantine lifted Oct. 19, about a month after the horse's Sept. 17 positive.

AAEP says that without testing, a recovered horse should be treated as infectious for up to 6 weeks after all signs are gone. The best test is a guttural pouch wash with a scope exam, which AAEP rates as about 50 times more likely to find the bacteria than a sample from the back of the nose (nasopharynx).

Some specialists advise keeping isolation areas closed until every horse tests negative, even if that takes six to eight months. Strangles is reportable in many US states, though rules vary by state, and your vet (sometimes with state officials) decides when restrictions lift.

Quarantine for new horses

For a horse joining a barn, AAEP recommends about 3 weeks of isolation with temperature checks; Merck's range is 14 to 21 days. Ideally, the newcomer also gets a guttural pouch test before joining the herd, especially if its history is unknown.

If strangles is confirmed at your barn

1. Don't move your horse out. Hauling a possibly exposed horse to another farm spreads the disease, and experts call it the No. 1 mistake owners make.
2. Learn the zones. Barns split horses into clean (green), exposed (yellow) and sick (red) groups with space between them. Work green first, then yellow, then red, or use different people for each group.
3. Take temperatures twice a day on exposed horses and log them. Call the vet about any fever; that horse usually moves to the sick area.
4. Keep gear separate. One set of buckets, brushes and tack per horse or zone, hand sanitizer at each stall, and gloves or dedicated clothes for the sick area.
5. Mind the hose. Don't let the nozzle touch the water in buckets or troughs, and keep hose handles clean.
6. Keep air moving. Don't shut horses in without ventilation, and skip pressure washers, which spray bacteria into the air.
7. Clean, then disinfect, then dry. Remove manure and bedding, scrub with detergent, apply a disinfectant your vet recommends and let surfaces dry completely. AAEP suggests resting pastures about 2 weeks in sunny, dry weather and up to 6 weeks when it's cold and damp.
8. Stay off other farms. Change clothes and boots before you visit other horses; farriers, trainers and vets should too.
9. Hold off on vaccinating mid-outbreak. AAEP and Merck both discourage it, and AAEP notes it raises the risk of complications like purpura hemorrhagica.

Treatment is your vet's call. Most horses need supportive care (soft feed, a clean, dry stall and time); antibiotics are saved for specific situations your vet identifies, partly because using them at the wrong time can keep a horse from building immunity. Never lance an abscess yourself.

Biosecurity checklist for boarders

Your daily habits

• Your own buckets, labeled. Don't lend them or borrow them.
• Your own grooming kit, halter, lead rope, tack and blankets. Clean them after shows and clinics.
• No nose-to-nose greetings with unfamiliar horses at shows, on trail rides or over fences.
• Wash or sanitize your hands between horses, especially if you help feed or turn out for others.
• Know your horse's normal temperature and keep a digital thermometer in your tack box. Check weekly, daily during local alerts, and for 2 to 3 weeks after your horse travels.
• Keep a returning horse apart after fairs, shows, sales or clinics when you can, or at least limit contact and watch temperatures for 2 to 3 weeks. Ontario's Wellington County foal got sick about 10 days after a fair.

Questions to ask your barn manager

• Do new horses quarantine for about 3 weeks in a separate area, with temperature checks or testing?
• Is there an isolation stall if a horse spikes a fever?
• How often are shared water troughs cleaned, and can each horse have its own bucket?
• How will boarders be told if there's a case?

Talk to your vet about the vaccine

Strangles vaccination is "risk-based," depending on your horse's exposure. In the US there are two types, a killed injectable and a modified-live intranasal vaccine, and availability differs in other countries.

Vaccines lower the risk but don't guarantee protection; Merck notes injectable products cut the clinical attack rate by about half. The intranasal version can make PCR tests read positive for up to 6 weeks, so tell your vet if your horse was vaccinated recently. All three Ontario horses were listed as unvaccinated, while one of October's Wisconsin cases was a vaccinated horse.

Brush up on normal vital signs and daily checks in our health basics and care guide.

What to watch next

• New EDCC alerts. Fall is moving season, with horses changing barns for winter, traveling to shows and selling. Check the public EDCC alerts page for your state or province.
• Quarantine updates from Morrow County, Oregon, Florida's Marion, Palm Beach and Orange county cases, the three Ontario farms and the Wisconsin, Kansas, Washington and New York cases flagged in September.
• Ontario cases. The Ontario Animal Health Network (oahn.ca) keeps a surveillance portal of past and current strangles cases in the province.
• Your own horse. Fever is the earliest warning. Because nasal shedding starts 2 to 3 days after the fever, isolating a horse at its first temperature spike can help keep it from exposing its neighbors.