If your horse suddenly has a fever, thick nasal discharge, and swelling under the jaw, your stomach drops. You start Googling strangles in horses and the worst-case scenarios fill your screen. I’ve been there, watching a barn mate spike a 104°F temp and burst into abscesses within ten days. Take a breath. Most horses recover fully from strangles with the right care, and this guide is built to walk you through what to do next.
Strangles in horses is one of the most common contagious equine diseases worldwide. It spreads fast through barns and show circuits, but it is also one of the most preventable respiratory illnesses in the horse world. In this guide, I’ll cover the early symptoms to watch for, what a vet actually does to diagnose it, how treatment really works day-to-day, and the biosecurity steps that stop an outbreak from taking down your whole barn.
Before we go deep, here is the scannable summary. Save it, share it with your barn manager, or print it for the tack room.
Table of Contents
Quick Facts: Strangles in Horses at a Glance
Cause: Streptococcus equi subspecies equi (S. equi) bacterium
Contagious period: Up to 6 weeks after symptoms start; carriers shed for months or years
Incubation period: 3 to 14 days after exposure
First sign: Fever of 103°F to 106°F, often before any other symptom
Hallmark sign: Abscesses under the jaw or behind the throat
Mortality rate: Less than 1% in uncomplicated cases; up to 30% if strangles spreads to other organs
Standard quarantine: Minimum 4 weeks after symptoms resolve, plus negative testing
What Is Strangles in Horses?
Strangles in horses is a highly contagious bacterial infection of the upper respiratory tract caused by Streptococcus equi subspecies equi. The disease gets its name because affected horses can struggle to breathe when swollen lymph nodes compress their airway. The Merck Veterinary Manual describes strangles as one of the most frequently diagnosed contagious diseases of horses worldwide.
The bacterium colonizes the lymph nodes around the throat, jaw, and upper airway. As those lymph nodes form abscesses, they swell dramatically, often bursting through the skin or draining into the guttural pouches. I have seen abscesses the size of softballs under a horse’s jaw, and the pressure alone can stop a horse from eating or drinking properly.
Most horses are exposed to S. equi at some point in their lives. Many recover without owners ever realizing they were infected. According to the UC Davis Center for Equine Health, around 30% of recovered horses become carriers, meaning they harbor the bacteria in their guttural pouches without showing signs and shed it intermittently. These silent carriers drive most barn outbreaks.
Why the Disease Matters
An outbreak can shut down a boarding stable for weeks. Show season gets cancelled, lessons are postponed, and veterinary bills pile up. Beyond the inconvenience, complications like bastard strangles, purpura hemorrhagica, and guttural pouch empyema can be life-threatening. Knowing how strangles works is the difference between a two-week scare and a multi-month crisis.
Early Signs and Symptoms of Strangles in Horses
The first signs of strangles in horses include fever, depression, and loss of appetite. These subtle symptoms typically appear 3 to 14 days after exposure, often before any visible swelling or discharge develops.
Here are the symptoms to monitor, in the order they usually appear.
Fever: Body temperature climbs to 103°F to 106°F, often the earliest sign
Depression and lethargy: Horse stands quietly, ears droop, and loses interest in surroundings
Anorexia: Refuses grain or hay, even when offered favorite feeds
Thick nasal discharge: Starts clear and watery, becomes thick yellow or cream-colored pus within days
Submandibular swelling: Firm, painful lumps develop under the jaw or behind the cheek
Difficulty swallowing: Horse extends the neck, drools, or coughs while eating
Respiratory noise or stridor: A loud, high-pitched wheeze when breathing severely affected horses
How Symptoms Progress
Day 1 to 3: A fever often spikes without visible swelling. This is the window where owners most commonly miss strangles.
Day 4 to 7: Nasal discharge thickens, and submandibular lymph nodes start swelling. The horse may look like it has a bullfrog under its jaw.
Day 7 to 14: Abscesses mature and either rupture on their own or require lancing by a vet. Most uncomplicated cases start improving after abscesses drain.
Day 14 to 21: Drainage continues, swelling shrinks, and fever resolves. The horse enters recovery, but it is still shedding bacteria.
How Strangles Spreads Between Horses?
Strangles spreads through direct contact with infected horses or contaminated equipment. The bacteria live in nasal secretions, pus from draining abscesses, and contaminated water troughs, brushes, and human hands.
According to the Equine Disease Communication Center, the bacteria can survive on surfaces for weeks in the right conditions. A single shared water bucket at a horse show can seed a barn-wide outbreak.
Common Transmission Routes
Horse-to-horse nose contact
Shared water troughs, feed buckets, and hay nets
Contaminated grooming tools, halters, and blankets
Humans moving between infected and healthy horses without changing clothes or washing hands
New arrivals that passed quarantine but turned out to be silent carriers
The Incubation Period
The incubation period ranges from 3 to 14 days, with most cases showing symptoms around day 6 to 8. During this window, an infected horse can spread the disease before anyone realizes it is sick. This is why routine temperature checks at shows and new arrivals are a real lifesaver.
Diagnosing Strangles: What Your Vet Will Do
Diagnosing strangles typically involves a physical exam plus laboratory testing to confirm Streptococcus equi equi. The classic swollen lymph nodes and fever are strong clues, but lab confirmation matters because other conditions can mimic strangles.
Here is what a typical diagnostic workup looks like.
Physical examination: Vet checks temperature, palpates submandibular and retropharyngeal lymph nodes, and inspects nasal discharge
Nasopharyngeal wash: Sterile saline is flushed into the nasal passages and collected for analysis
PCR testing: Polymerase chain reaction detects S. equi DNA in 24 to 48 hours
Bacterial culture: Gold standard for confirming live bacteria, but takes 2 to 5 days
Guttural pouch endoscopy: Used in chronic or carrier cases to look for chondroids (inspissated pus balls)
I recommend asking for both PCR and culture if your vet suspects strangles. PCR is faster but only detects bacterial DNA, which can stay positive after the horse has cleared the infection. Culture confirms the bacteria are alive and still being shed.
Treatment Options for Strangles in Horses
Treatment for strangles in horses focuses on supportive care, abscess management, and strategic antibiotic use. Most cases resolve with good nursing and hygiene, but complicated cases need more aggressive intervention.
The AAEP guidelines emphasize that antibiotics are not always the right answer for strangles. Using them at the wrong stage can actually slow abscess maturation and prolong the disease.
Supportive Care Essentials
Provide a clean, dry, well-ventilated stall away from other horses
Offer soaked hay pellets or senior feed if the horse struggles to chew
Apply hot packs to swollen lymph nodes to encourage maturation
Flush the nasal passages with saline to keep them clear
Monitor temperature twice daily
When Vets Use Antibiotics
Antibiotics like procaine penicillin work best in early strangles cases before abscesses form, or in horses with severe systemic illness. They are generally avoided once abscesses are draining because they can prolong the carrier state. Bastard strangles (where infection spreads to other organs) almost always requires aggressive antibiotic therapy.
Abscess Drainage
Most abscesses need to be lanced and flushed once they mature. Your vet will make a small incision, drain the pus, and flush the cavity with diluted povidone-iodine or chlorhexidine. Do not try to lance abscesses yourself. Premature drainage can push infection deeper and create a draining tract that takes weeks to heal.
Average veterinary costs for an uncomplicated strangles case run $500 to $1,500, including exams, diagnostics, and follow-ups. Complicated cases with guttural pouch involvement or systemic spread can climb well past $5,000.
When to Call the Vet Immediately
Call your vet right away if your horse has trouble breathing, stops eating for more than 24 hours, or runs a fever above 104°F. Strangles can escalate from mild to life-threatening within hours, especially in young, old, or immunocompromised horses.
These warning signs require emergency veterinary attention.
Open-mouth breathing or gasping
Gums turning purple or brick-red
Refusal to drink for more than 12 hours
Severe depression, leaning on walls, or unable to stand
Swelling that blocks vision or extends behind the eye
Blood-tinged nasal discharge or bleeding from the nose
Sudden swelling in the abdomen, limbs, or chest (signs of bastard strangles)
Trust your gut on this. I have watched owners wait “just one more day” with a horse that was struggling to breathe, and that delay can mean the difference between recovery and a fatal airway obstruction.
Complications: Bastard Strangles and Carrier Horses
Most strangles cases resolve without complications, but a small percentage develop life-threatening issues. Knowing the risks helps you catch problems before they become emergencies.
Bastard Strangles (Metastatic Strangles)
Bastard strangles happens when S. equi spreads beyond the head and neck to the abdomen, lungs, kidneys, or even the brain. Abscesses form internally and rupture, leading to peritonitis, pleuritis, or sudden death. Mortality rates for metastatic strangles range from 30% to 60%. Warning signs include colic, weight loss, and recurrent fevers weeks after initial recovery.
Purpura Hemorrhagica
This immune-mediated complication causes small blood vessels to leak, leading to swelling in the legs, belly, and face. It can damage the kidneys and heart. Horses that have had strangles before may develop purpura with future infections.
Carrier Horses
Approximately 10% to 30% of recovered horses become carriers, harboring S. equi in their guttural pouches for months or years. These horses look completely healthy but shed bacteria intermittently, seeding new outbreaks. Three negative guttural pouch washes or endoscopic samples taken at least one week apart are needed to confirm a horse is no longer a carrier.
Strangles Recovery Timeline: What to Expect
Recovery from uncomplicated strangles takes 3 to 6 weeks, depending on the horse and how quickly abscesses mature. Knowing what to expect day by day helps you stay patient and catch setbacks early.
Day-by-Day Recovery Guide
Days 1 to 7: Fever peaks, abscesses form and mature. Expect heavy nasal discharge and continued swelling.
Days 7 to 14: Most abscesses rupture or get lanced. Fever should resolve within 48 hours of drainage.
Days 14 to 21: Drainage slows, swelling reduces, and energy returns. Continue isolation.
Days 21 to 42: External wounds heal, but the horse may still shed bacteria. Confirm with negative PCR and culture before ending quarantine.
Day 60+: Carrier retesting via guttural pouch wash or endoscopy before returning to group housing.
Horses are typically not contagious once three negative nasopharyngeal washes are obtained two weeks apart. Many boarding barns require three negative PCR tests before allowing a recovering horse back into the herd.
Prevention and Biosecurity: A Practical Checklist
Preventing strangles is far easier and cheaper than managing an outbreak. A solid biosecurity plan protects your horse, your barn, and your boarding income if you run a facility.
Quarantine New Arrivals
Isolate all new horses for a minimum of 21 days, though many vets now recommend 28 to 30 days for strangles specifically. During quarantine, monitor temperature twice daily, treat for parasites, and confirm vaccination history. Run a baseline PCR test before introducing the horse to the herd.
Disinfection Protocol
S. equi is susceptible to most common disinfectants when used properly.
Use phenolic disinfectants like Phenol 256 or diluted bleach (1:10) on hard surfaces
Wash fabric equipment with hot water and bleach at 140°F or higher
Disinfect shared tools, troughs, and fences between horses
Remove organic debris before disinfecting; biofilm protects bacteria
Restrict access by unnecessary visitors during outbreaks
Rotate pastures when possible. S. equi survives in soil and water for weeks, especially in cool, moist conditions.
Vaccination Strategy
Strangles vaccines reduce disease severity but do not guarantee immunity. Two main options exist: an intranasal modified-live vaccine and an intramuscular M-protein extract vaccine. Intranasal vaccines tend to produce stronger local immunity but can occasionally cause mild strangles-like symptoms in vaccinated horses.
The AAEP does not recommend routine vaccination in low-risk closed herds. Vaccination makes more sense for show horses, lesson horses, and horses that travel frequently. Always base vaccination decisions on a conversation with your vet about your specific situation.
Show and Travel Hygiene
Bring your own water buckets, avoid shared communal troughs, and do not let your horse touch noses with strangers. Wash your hands and change clothes before moving between barns. These small habits stop most outbreaks before they start.
Frequently Asked Questions
Can a horse recover from strangles?
Yes, most horses recover fully from strangles. Uncomplicated cases resolve in 3 to 6 weeks with proper supportive care, abscess drainage, and quarantine. Mortality rates stay below 1% for typical strangles, though complicated cases like metastatic strangles have higher fatality rates.
Can strangles be passed by humans?
Humans can mechanically transmit strangles between horses through contaminated hands, clothing, and equipment. The bacterium does not cause illness in people, but it survives on human skin and gear long enough to spread the disease from one horse to another.
What are the signs of strangles in horses?
Early signs include fever of 103 to 106°F, depression, and loss of appetite. Within days, horses develop thick yellow nasal discharge, swelling under the jaw, and abscesses that may rupture and drain pus. Some horses also cough, drool, or breathe noisily as swelling compresses the airway.
How do you get rid of strangles?
Strangles is managed with strict quarantine, supportive care, abscess drainage when needed, and targeted antibiotic use in early or severe cases. Three negative PCR tests or guttural pouch washes, taken at least two weeks apart, are required before a horse is cleared to return to the herd.
Can humans catch strangles from horses?
No, strangles does not infect humans. The bacterium Streptococcus equi equi is host-adapted to horses, so people cannot develop strangles. That said, humans can spread the bacteria on their hands and clothing between horses, which is why strict hygiene matters during outbreaks.
How long is strangles contagious in horses?
Strangles is contagious from about 3 days after exposure until at least 4 to 6 weeks after symptoms resolve. Carrier horses can shed the bacteria intermittently for months or even years, which is why three negative tests over several weeks are needed before ending isolation.
Final Thoughts on Strangles in Horses
Strangles in horses is scary when you first face it, but knowledge takes the panic out. Most horses come through this disease with nothing worse than a few weeks of isolation and a story to tell. Watch for the early fever, isolate the horse quickly, confirm the diagnosis with your vet, and commit to the full quarantine timeline. With a thoughtful plan, you can protect your horse and the rest of your barn from a single case.
Take a deep breath, take the temperature twice a day, and reach out to your veterinarian at the first sign of trouble.