Strangles: Know the Facts

Stranges is a common disease of horses and strikes fear into the majority of owners! It is a highly contagious infection of the upper respiratory tract of equines caused by a bacterium, Streptococcus equi var. equi. It can affect any type, gender and age of horse, pony or donkey. 

The disease is known for it's severe inflammation of the mucosa of the head and throat, with swelling and often rupture of the lymph nodes, which produces large amounts of pus.


Causes

It is caused by a bacterium, Streptococcus equi var. equi.


Transmission

The bacteria enters via the respiratory tract where it then travels to the lymph nodes. The lymph nodes swell and may rupture, spreading the bacteria into the environment. The bacteria can be transferred between horses by direct contact (such as nose to nose contact). It can also be spread indirectly via people's hands, clothing, farrier equipment, shared water troughs, feed buckets and equipment, tack and yard equipment. It is thought that the bacteria can survive in water for several weeks.

The incubation period is up to 14 days (usually 3-10 days), but abscesses form one to two weeks following infection.

Around 10% of former strangles sufferers show no signs or symptoms of the disease but are carriers of the bacteria. These carriers can randomly shed bacteria for months and possibly years. This means they can pose a risk to other horses throughout their lifetime!

Thick, yellow nasal discharge

Symptoms

• Temperature above 38.5°C (typically rises to 41°C)
• Depression
• Lack of appetite
• Nasal discharge that develops into a thick, yellow mucus
• Swollen or enlarged lymph nodes in the neck and throatlash
• Possibly have a slight cough 
• Horses are often seen positioning their heads low and extended, so as to relieve the throat and lymph node pain. 
• Some horses have trouble breathing and swallowing (hence the name "strangles")

Susceptible horses develop strangles within 3–14 days of exposure.

As the disease progresses, abscesses usually develop in the submandibular (between the jaw bones) and/or retropharyngeal (at the back of the throat) lymph nodes. The lymph nodes become enlarged, hard and and very painful and often make breathing difficult. The lymph node abscesses will burst (or may be lanced) in 7–14 days, releasing thick highly infectious pus. The horse will usually rapidly recover once abscesses have ruptured.

Strangles has a 1% mortality rate.


Treatment 

The vast majority of horses with strangles will recover and it has a very low mortality rate. Some horses will be given anti-inflammatory drugs to control pain and aid appetite. A hot compress will bring the abscess to a head and encourage it to burst. A vet may lance the affected lymph nodes. Antibiotics aren't very effective once an abscess has developed.

Letting the disease run its course will offer some immunity against future disease.

Submandibular Lymph Node Abscess 

Prevention and Control of Infection

• Isolation of new horses for 4-6 weeks.
• Cases of suspected strangles should be taken seriously and horses should be isolated immediately until proven not to have the disease. An isolation period of 6 weeks is usually necessary to ensure that the disease is not still present before ending the isolation.
• Tools and equipment should not be shared with 'healthy' horses.
• Hands should be washed after handling or being near affected horses. Clothes should be washed on a hot cycle. 
• Let people such as the farrier, dentist, vet etc know before they come to the yard. They may arrange to see you last thing of day to avoid spreading the bacteria to other yards.
• Warn horse owners and livery yards. 
• Avoid holding or taking horses to shows where they may spread the disease to other horses and yards.