English
Strangles, also known as equine distemper, is a highly contagious disease caused by the bacteria Streptococcus equi.
Young horses are most susceptible to developing strangles disease. This condition most commonly occurs in horses under the age of two. [1]
The name “strangles” comes from the common sign of dysphagia or trouble swallowing that some horses experience, caused by enlarged lymph nodes.
If severe enough, horses can suffocate leading to death. However, the severity of the disease varies greatly and is dependent on the status of the horse’s immune system.
The first written record of strangles was in 1251, reported by an officer in the imperial court of Emperor Frederick II in Italy.
Despite modern improvements in the health and management of horses, strangles continues to be one of the most frequently diagnosed infectious diseases of horses worldwide. [2]
Symptoms of Strangles in Horses
Most horses display classic signs of strangles, but not every horse has the same symptoms.
Younger horses usually show more severe signs and typically develop lymph node abscesses on the head and neck.
Other common symptoms of strangles include fever and lethargy. Fever is often persistent and may exceed 42oC (107.6oF).
Horses can also develop inflammation of the pharynx, which can lead to a reluctance to eat or drink. They may stand with their necks extended and appear depressed. [2]
Nasal discharge, as well as discharge from the eyes, is also common. Some horses will develop a cough which may be associated with eating. Horses may expel discharge from the mouth or nose with coughing or eating as well. [3]
Lymph Node Abscesses
Lymph node abscesses usually rupture and drain into the guttural pouches (at the back of the jaw, behind the eye).
The guttural pouches then drain into the nasopharynx between 7-28 days after infection. This results in the profuse nasal discharge that strangles is well known for.
Once the abscesses drain, the infection is usually resolved. In fact, most horses with equine distemper recover over a period of weeks. [2]
Expulsion of large amounts of discharge from the mouth or nose with coughing, eating, or a lowered head position suggests a collection of pus (empyema) in the guttural pouch. [3]
Prognosis & Antibody Protection
Older horses can contract strangles as well, but are usually less severely affected than younger horses and recover more quickly.
Older horses, as well as weanlings with waning maternal antibody protection, can develop a mild form of the infection called catarrhal or atypical strangles. [3]
Horses affected by catarrhal strangles often display mild respiratory symptoms, but do not develop abscesses.
If the dam has recovered from strangles or has been recently vaccinated, young foals are often protected by ingesting immunoglobulins (antibodies) in the dam’s milk.
These antibody proteins coat the upper respiratory tract and mucous membranes of the mouth. [4] The foals will continue to be protected until weaned. [3]
Unfortunately, however, 20-25% of horses recovering from strangles can suffer a second attack of the disease within several months. [3]
How Strangles Spreads
Equine distemper can occur at any time throughout the year but tends to occur more in Spring. [5]
This infection is highly contagious and often affects multiple horses on the same farm. Fatality rates can be as high as 8 or 9% in large farm outbreaks. [3]
Nasal shedding of S. equi bacteria usually begins 2-3 days after onset of fever and often persists for 2-3 weeks. Some horses can shed the bacteria for much longer if infection persists in the guttural pouch or sinus cavity.