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What is strangles?

Strangles in horses is a respiratory bacterial infection caused by Streptococcus equi. Strangles gets its name from its characteristic symptom of enlarged lymph nodes surrounding the upper airways, which can cause horses to suffocate.

Strangles remains widespread today. It is one of the most commonly diagnosed equine infectious diseases worldwide.

Loss of appetite is a sign of strangles

How is strangles in horses contracted?

Between horses via nasal discharge

Strangles is highly contagious and is transmitted directly between horses via the nasal discharge of an infected horse. Horses can shed the bacterium for months or even years without showing signs or symptoms, while still transmitting it to other horses.

Indirect transmission is also possible if equipment or objects become contaminated and are shared between horses, or by a handler who has hands or clothing contaminated by an infected horse.

Clinical signs and symptoms of strangles in horses

Clinical signs and symptoms of strangles include:


Nasal discharge

Swollen lymph nodes

(typically submandibular and retropharyngeal) that can develop abscesses

Difficulty swallowing

Loss of appetite

Occasionally the infection spreads to lymph nodes in the thorax or abdomen, resulting in a complication known as "bastard strangles."

Prevention and treatment of strangles in horses

The traditional treatment for strangles in horses is a course of antibiotics, such as penicillin, although the efficacy of this treatment remains controversial. Antibiotics are ineffective at eliminating the microbe completely and may result in a reduced immune response, potentially making horses treated with antibiotics more susceptible to relapse.

Vaccination helps to reduce the risk of strangles. Strangles is highly contagious and will inevitably infect all exposed horses. In addition to vaccination, following a strict biosecurity protocol can help reduce the risk of a strangles outbreak or minimize the impact of an emerging outbreak.

A strangles control protocol may include:

Daily monitoring of the temperature of horses that may have come in contact with strangles.
Immediately isolating
any horse showing signs of infection. Horses will develop a fever as early as two days before they begin to shed the bacteria.
Isolating new horses on a property for two weeks following their arrival.
Regular cleaning and disinfecting of equipment and facilities.
Talk to your veterinarian

about whether a vaccination plan to help protect your horse against strangles is needed.