Learn About Equine Strangles

Causes, Symptoms and Treatment

Veterinarian examining horse
Your vet can help you determine if your horse has strangles. Caiaimage/Agnieszka Olek / Getty Images

Strangles (Streptococcus equi, Equine Distemper) is one of the most common respiratory illnesses in horses. When strangles go through a barn it is a cause for concern. The barn can be shut down for weeks because quarantine is required to prevent the spread of the disease. Although strangles is not generally fatal, and most horses recover fully, there are the occasional complications that can lead to death. Vigilance and hygiene are the most important tools when guarding against or treating strangles.

Many stables have strangles run through them, and although there was expense, stress, and inconvenience, no fatalities result. Some veterinarians go so far as to suggest that strangles, especially in young stock, is somewhat like chicken pox in children—uncomfortable and inconvenient, but with good care, there is little risk of any serious outcome. It is untrue that strangles only runs through dirty barns and dealer or feedlots. While horses with weakened immune systems and in crowded quarters may be more susceptible, strangles like lice, is fairly democratic about what horses and stables it effects.

Causes of Strangles

Strangles is caused by an easily transmissible bacterium called Streptococcus equi. The bacteria can easily be carried from horse to horse, by human hands and clothing, brushes, buckets and persist on stable surfaces for weeks. Young horses are more susceptible to strangles than mature horses over five years of age, although horses can contract strangles at any age, especially if their immune system is already weakened. Because the bacteria is so easily transmissible, one horse can quickly infect a whole stable, or one horse at a horse show can spread the illness more widely. Any environment where horses are coming and going frequently is ideal for the spread of strangles.


It may only take a few days from the time of infection to when actual strangles symptoms are evident. Horses that have been infected with Streptococcus equi will quickly go off their feed. The horse's temperature will rise rapidly to (103-106°F [39.4-41.1°C]) from the normal of 98.5F to 101F (36.9C to 38.3C). This is why it is important to know what your horse’s normal TPRs are, so you can determine what is normal and what is not.

The horse may develop a wet cough and its breathing may sound raspy and strained. The normal clear mucous in its nostrils turns to yellowish green and may become copious. A bit of clear mucus is normal. Thicker, colored mucus is not. You may be able to feel swelling between the lower jaw bones and the swelling can fill the area behind the cheekbone, all the way down the sides of the face. The swelling may become quite hard and distended and can eventually rupture. The swelling may also obstruct the horse’s breathing, hence the name ‘strangles’ and the noisy breathing. Older horses, who may have partial immunity may only show mild symptoms.

There are three complications that can occur that may be fatal. Bastard strangles is when the infection travels to other places in the body like the brain, stomach, or lungs. The lymph nodes in those areas can then rupture with fatal results.

Purpura hemorrhagic can occur, this is an inflammation of the blood vessels that can occur when the animal is recovering causing edema or swelling of the head, legs or other areas of the body.

Horses generally recover in about three weeks but stay contagious for up to six weeks or more. But a horse may also become a carrier, carrying the infection in its glands, and potentially infecting any other horse that comes in contact with.

There are several other problems that can occur that are worrisome, but not necessarily, fatal including inflammation of the heart muscle, anemia, tissue inflammation and paralysis of the throat muscles that can cause roaring—loud raspy breathing when the horse is working hard.


Strangles can be easily diagnosed by a veterinarian by testing the nasal mucus. If it is possible to catch the illness in its very early stages, penicillin can be administered with good results. However, as the illness progresses, antibiotics are less effective and may even cause complications such as bastard strangles. With or without antibiotics, good care that includes scrupulous hygiene is essential. Any burst lymph nodes should be allowed to drain and cleaned with the antiseptic recommended by your veterinarian.


If a horse suspected to have strangles quarantine is necessary. Any new horse to a stable should be kept separate to make sure it has no diseases to pass along. Anything that comes in contact with a sick horse, equipment including feed and water buckets, brushes, blankets, human hands should be well cleaned.

Vaccinations are available, but so far, their lifespan is very short so they effective only in the short term. If a stable is infected with strangles it should be closed to new horses and people should be advised to take precautions. This includes avoiding contact with horses and gear and washing hands and equipment carefully if contact does take place. Horses should not travel anywhere they might spread the disease, even if they appear to be recovered. Horses with taken to events or moved between stables can easily cause outbreaks. 


Hayes, M. Horace, and Peter D. Rossdale. Veterinary notes for horse owners: an illustrated manual of horse medicine and surgery. 17th ed. New York: Prentice Hall Press, 1987. Print.