Equine Strangles

An extremely contagious respiratory infection this disease is certainly feared by the majority of equine owners. Strangles is caused by the bacteria Streptococcus equi. Horses, ponies donkeys, mules and other members of the equine family are at risk. Death can occur as a result of the disease and with fatalities resulting in approximately one infected horse in every hundred. Unvaccinated horses in high risk areas are most at risk of catching strangles. Strangles spreads incredibly quickly and so is a major threat if a horse becomes infected.

Transmission occurs both directly and indirectly. Recovered horses are still able to act as carriers of the disease. The more well-known symptoms are the presence of abscesses which, in a condition known as “bastard strangles” can lead to the horse dying. The disease is only transferable to humans (zoonotic) in people who have a compromised immunity. Despite this, cases of human infection are rare. Vaccination is strongly encouraged for horses in high risk areas or where a case of strangles has suddenly presented itself. However, there are some adverse side effects from the vaccination.


Through direct contact, the strangles bacteria enter the horse’s body orally. Contact with infected discharge from the nasal cavity or from the abscesses of an infected horse can also further transmit the disease. Indirectly, fomites can be a source of infection. These include contaminated tack, clothing, footwear, and buckets. Surfaces such as wooden fences and doors can also transfer the disease.  The infected horse should be quarantined and all items or surfaces used around the horse which have even the slightest possible chance of being contaminated should be disinfected and kept away from other animals. Outside the host, the bacteria can survive for as long as two months.


The mild form of strangles commences with an elevated temperature, a loss of appetite and depression. Serous nasal discharge is present and as the disease progresses it become viscous and yellow in colour. There is a swelling of the lymph nodes and abscesses form. The most severe type of strangles is called “bastard strangles”. This is where the abscesses form in various other areas of the horse’s body. These include the liver, kidneys, and lungs.

Treatment and Prevention

There is no cure as such for strangles. Supportive therapy is used to aid the horse’s immune system to combat the disease itself. Antibiotics are rarely used unless to treat a secondary infection. The abscesses may be washed out with an antiseptic recommended by the vet.

Routine vaccinations should be given to the horse to provide long term protection against strangles. Vaccination is often only given to horses in high risk areas although, if the vaccine is injected into the muscle, then swelling in this area may occur. Other side effects are present such as a high temperature and even the presence of abscesses. Vaccinations are now available where the vaccine is squirted up the nose. In the majority of cases, excluding pregnant mares, it may seem that this offers relatively the same amount of protection and with fewer side effects.

Diagnosis and Prognosis

Strangles is diagnosed by the clinical signs presented but nasal and throat swabs can be taken to confirm its presence. The bacteria are isolated, cultured, and identified. The discharge or puss from abscesses is also used. The polymerase chain reaction test can be used to identify the bacteria Streptococcus equi. Following supportive therapy, the prognosis for strangles is good with most horses recovering well. However one in a hundred horses can die from infection.


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