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Strangles: A Contagious Equine Disease

By Written by Josie Traub-Dargatz, DVM, MS, DACVIM

What is "strangles?" 

Strangles is a highly contagious disease of equids including horses, donkeys and ponies.  It is caused by the bacteria Streptococcus equi, often abbreviated Strep. equi or S. equi. It is called "strangles" because of the strangled breathing sounds the ill horse makes as a result of profuse nasal discharge and the swellings that form in the head and neck region. 

How serious is it? 

Most animals fully recover from strangles in two to four weeks. Although enduring immunity against re-infection is variable, in some equids it can last for years.  However, not all horses develop a protective immunity upon recovery.  Some horses, although they appear healthy, shed the bacteria in nasal secretions for a prolonged period and can infect nearby horses. Horses can die from strangles due to asphyxiation or “strangling,” as well as from other complications. 

How common is strangles? 

Strangles is highly contagious. It can spread rapidly from animal to animal and is one of the more common bacterial infections of horses. 

How does it spread? 

The disease is spread via nasal secretions (snorting, coughing, physical nose-to-nose contact) and pus from draining abscesses.  It is possible for humans to spread the disease through contaminated clothing, hands or equipment, etc. The bacteria can contaminated water or feed sources and be transmitted orally as well as via the respiratory tract.

What should I do if I have a strangles outbreak in my horses? 

Contact your veterinarian, stop horse movement until the outbreak is resolved, and work with your veterinarian to determine the need for follow-up visits to check for bacterial shedding. 

What should I watch for? 

Typical clinical signs begin with mild lethargy, reduced feed intake, slight cough, nasal discharge and a fever. For adults a rectal temperature over 100.5 degrees Fahrenheit or for foals over 101.5 degrees Fahrenheit would be considered a higher than normal temperature or a fever.  

In most cases, a few days after the onset of fever and more mild signs, the lymph nodes swell and form abscesses around the throat, as well as in some cases under or around the base of the ear. 

At first, the nasal discharge is clear then becomes cloudy and whitish. After the abscesses have ruptured and drained into the nasal passages the discharge usually becomes purulent (thick white to yellow).  

Horses are often seen positioning their heads low and in an extended position in order to relieve the throat and lymph node pain.  

Some of the abscesses may rupture through the skin. Be aware that the pus from the nose and draining abscesses is highly contagious to other horses.

It is important to keep in mind that not all cases develop the “classic” abscess formation. Some horses may just develop a fever and be off feed for a few days.

Without complications recovery begins, in most cases, after abscesses drain or infection begins to be resolved by the body.  

If I suspect my horse has strangles, what should I do?  

The first thing to do is to isolate any horse with signs of strangles from other horses.  Supportive care of the animal includes: 

·   Keeping the horse dry and protected from extreme cold or heat 

·   Providing soft, palatable feed 

·   Monitoring the horse’s body temperature 

·   Contacting your veterinarian to describe the signs being shown by the horse, and get their advice on further management of the horse’s illness including diagnostic testing and treatment options 

·   Apply hot compresses to abscesses to promote rupture and drainage 

Finally, if complications arise such as purpura (a severe vasculitis resulting in swelling in legs and ventral abdomen as well has hives), internal abscesses or muscle problems, the best course of action is to contact your veterinarian for assistance. 

Is there a vaccine against strangles? 

Yes, there are several different vaccines and they can be used to help protect horses from strangles.  However, they do not fully protect every horse from infection. Discuss vaccination options with your veterinarian to determine if the benefits of vaccination outweigh the risks and cost.      

How can I minimize the risk of strangles at my facility? 

·      Have a biosecurity policy for people and horses coming onto your operation, and avoid contact with horses of unknown health status or those that are ill. 

·      Don't overstock your equine facility. 

·      If new horses are introduced, request a statement by a veterinarian regarding their health status including any recent exposure to contagious diseases. If there is any history of strangle disease or exposure to other horses with strangles consult your veterinarian regarding options for testing to determine if the horse is shedding Strep. equi. Keep newly arrived horses isolated for a few weeks to observe them for signs of illness.  

·      Personnel attending to horses must take great care not to move from isolated horses to the other horses on the establishment, without taking appropriate precautions. 

·      Don't share tack, feed tubs, water containers, trailers, pens or stalls used by horses of unknown health status. 

·      The organism is not thought to have extended persistence in the environment, however the exact duration of persistence is not known. Surfaces that are nonporous can be cleaned with soap and water, rinsed and then disinfected. Consult with your veterinarian regarding how best to disinfect surfaces in an equine facility. Special attention should be paid to the water containers that may have been contaminated with pus from ill horses. 

·      Horses with a history of strangles can be tested to determine if they are shedding Strep. equi. Ask your veterinarian about the need for such testing of new arrivals.


Reviewed and updated by original author in 2016.