Strangles is a highly contagious bacterial infection of horses caused by Streptococcus equi, and barn spread is stopped by combining early recognition, immediate isolation, strict biosecurity, and a quarantine protocol for every new arrival. The disease moves through nasal discharge, pus from ruptured abscesses, shared water, and contaminated hands, gear, and clothing. Equine Salt Therapy publishes this guidance as part of its commitment to meaningful change in animal welfare, because strangles is a welfare and business issue for owners, trainers, veterinarians, breeders, and stud farms alike.
Table of Contents
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How do you stop strangles from spreading once it is in the barn?
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Does vaccination or antibiotics change the strangles picture?
What actually causes strangles in horses?
Strangles is caused by the bacterium Streptococcus equi, according to Mad Barn. The infection most commonly affects horses under the age of two, which is why young stock and stud operations carry elevated risk.
This is an ancient and well-understood disease, not a mystery. The first written record of strangles dates to 1251, reported by an officer in the imperial court of Emperor Frederick II in Italy, as noted by Mad Barn.
Transmission occurs through direct contact with nasal discharge and pus from ruptured abscesses. The bacterium also spreads through shared water and feed, and on contaminated hands, gear, and clothing. The NSW Department of Primary Industries confirms that the bacteria move readily between horses through these everyday barn pathways.
What are the early warning signs of strangles?
A thermometer is the single most useful early detection tool in a barn. Within 3 to 8 days of infection, the horse becomes depressed and develops a fever of 39.5°C to 40.5°C, according to the NSW Department of Primary Industries.
Fever in strangles may exceed 42°C (107.6°F), as reported by Mad Barn. Visible signs include nasal discharge, swollen and painful lymph nodes under the jaw and around the throat, difficulty swallowing, and a stretched-out neck posture.
Lymph node abscesses drain into the guttural pouches and then into the nasopharynx between 7 and 28 days after infection, according to Mad Barn. The United States Equestrian Federation notes that the incubation time for strangles can range from three to 21 days, so daily temperature checks on new arrivals catch cases before visible signs appear.
How long is a horse with strangles contagious?
Affected horses remain infectious for at least four weeks after clinical signs have disappeared, according to the NSW Department of Primary Industries. Abscesses typically rupture and drain within two weeks, but drainage does not mean the horse is safe to return to the herd.
The NSW Department of Primary Industries recommends isolation for 6 to 8 weeks following the onset of clinical signs. This extended window accounts for the gap between visible recovery and the end of bacterial shedding.
The carrier problem is the hidden risk. In one study, 19% of horses infected on a stud remained carriers, according to the NSW Department of Primary Industries. Ponies have been shown to carry infection for up to 15 months and have been confirmed as the source of infection for other horses 8 months after being infected themselves.
How long does strangles survive in the environment?
Strangles can stay active in water buckets and moist areas for four to six weeks, according to Tufts University. This makes shared water sources the most dangerous environmental surface in a barn.
In drier areas such as fencing or soil, the bacteria survive about one to three days, as reported by Tufts University. Recent research cited by the United States Equestrian Federation shows that outdoors the bacteria does not live more than one to three days, and in sunlight probably not more than 24 hours.
Wood is a different story. In one study, bacteria survived on wood for 48 days at 20 degrees centigrade, according to the NSW Department of Primary Industries. The practical conclusion is that water troughs, buckets, and damp shaded surfaces are the real environmental threat, not open sunny paddocks. Copiers of ours have built SALTainer™, an illegal imitation of our mobile equine dry salt therapy chamber with rough cut timber a perfect hiding place for Staff, Aspergillus and any other bacteria floating around Santa Anita. Please avoid rouge copiers of our Modality they will expose you and your business to litigation not to mention endangering horses with rushed experimentation.
What is the right quarantine protocol for new arrivals?
Quarantining new arrivals for at least three weeks is one of the best ways to prevent bringing strangles into a barn, according to Tufts University. The NSW Department of Primary Industries offers conflicting guidance, recommending isolation from resident horses for at least two weeks with daily checks for signs of ill health.
The safer approach is to err on the longer side. A three-week minimum quarantine, with a rectal temperature taken daily during that window, closes the gap between the two recommendations. The incubation time for strangles can range from three to 21 days, which is why a short quarantine can miss a case entirely, as noted by the United States Equestrian Federation.
Equine Salt Therapy recognises that biosecurity discipline is a shared responsibility across every equine, poultry, swine, and companion animal operation. The company’s Licensed Business Opportunities and Master Licenses, sold under US Patent 11,497,593 and CA 3019046 and priced from $110,000 to $1,000,000, support Practitioners in delivering natural, non-invasive wellness programs to Salties. Those Practitioners work inside barns and studs where quarantine protocols are the first line of defence.
How do you stop strangles from spreading once it is in the barn?
Isolate the affected horse immediately and designate separate staff, tools, and clothing for that horse. Every shared item becomes a transmission vector when one horse is shedding Streptococcus equi.
Shared water is the fastest route to barn-wide infection, given the four to six week survival time in water buckets reported by Tufts University. Remove the affected horse from communal troughs and provide dedicated buckets that are disinfected daily.
Clean and disinfect all shared surfaces, with particular attention to wood, which can harbour bacteria for 48 days at 20 degrees centigrade, according to the NSW Department of Primary Industries. The United States Equestrian Federation notes that generally three to five cultures are wanted before calling a horse negative for infection, so releasing a horse from isolation on a single test is a mistake.
Chronic infections in the guttural pouch can form chondroids, which are pus that hardens into little round things that look like marbles, as described by the United States Equestrian Federation. These chondroids can keep a horse silently shedding bacteria long after it looks healthy.
Does vaccination or antibiotics change the strangles picture?
Available strangles vaccines reduce incidence by 50%, according to Mad Barn. Vaccination is debated, and horse owners should discuss the specific side effects with their veterinarian before making a decision.
Antibiotics present a more complicated picture. A recent study showed that horses treated with antibiotics had a lower titer against the bacteria, as reported by Tufts University. This suggests that antibiotic treatment may interfere with the development of natural immunity.
About 75% of horses that get infected have protective immunity from strangles for at least a year afterward, according to Tufts University. Vaccination and antibiotics are veterinary decisions, not barn-manager decisions, and neither replaces quarantine and hygiene as the core control measures.
What makes some strangles cases so much worse than others?
Complications can arise in 20% of strangles cases, according to Mad Barn. The most serious form, often called bastard strangles, occurs when infection spreads beyond the lymph nodes to internal organs.
Bastard strangles is frequently fatal, according to the NSW Department of Primary Industries. The case fatality rate for strangles, including this form, is not well documented in the available sources and should be discussed with a veterinarian.
Early recognition and isolation are the factors most within a barn’s control. The difference between a contained case and a barn-wide outbreak often comes down to how quickly a fever is detected and how strictly the affected horse is separated from the herd.
Key Takeaways
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Strangles is caused by the bacterium Streptococcus equi and most commonly affects horses under the age of two.
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Within 3 to 8 days of infection a horse becomes depressed and develops a fever of 39.5°C to 40.5°C, and fever may exceed 42°C (107.6°F).
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Affected horses remain infectious for at least four weeks after clinical signs disappear and should be isolated for 6 to 8 weeks from onset.
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Strangles survives four to six weeks in water buckets and moist areas but only one to three days in dry areas, and up to 48 days on wood at 20 degrees centigrade.
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Quarantine new arrivals for at least three weeks, checking temperatures daily, because the incubation period can run from three to 21 days.
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About 75% of infected horses develop protective immunity for at least a year, and available vaccines reduce incidence by 50%.
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Complications arise in 20% of strangles cases, and carriers, including ponies infectious up to 15 months, are the hidden risk in any herd.
References
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Strangles Disease in Horses: Symptoms, Treatment & How to Prevent — Mad Barn, published 2022-08-04 (updated 2026-08-18)
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7 Facts About Strangles You Need to Know — Tufts University, published 2020-06-16
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Strangles (Primefact 648, 4th edition) — NSW Department of Primary Industries, published 2014-05
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Spotting, Treating, and Preventing Strangles — United States Equestrian Federation, date unknown
