What is Strangles in horses?

Strangles in horses is a highly contagious upper respiratory tract infection caused by the bacteria Streptococcus equi. It affects horses, donkeys and ponies of all ages, breed and sex. The bacteria often infect the lymph nodes around the jaw, causing them to become swollen.

What causes strangles?

Strangles is an infectious disease caused by a streptococcal bacterium, Streptococcus equi. The bacterium is found in the nasal discharge of sick horses and is spread when a sick horse coughs and sputters. It is also found in the pus from ruptured lymph nodes. The infection can be spread directly or indirectly - directly by a sick horse greeting other horses, or indirectly, through people, furniture or utensils that have been in contact with sick horses. The incubation period is 3-14 days.

What are the symptoms of strangles?

Nowadays, it is common for strangles to progress with much milder symptoms. A fever, cough and runny nose, as with any cold, can be strangles. This means that it can be easy to miss outbreaks of the disease. The symptoms to look out for include:

Fever
Decreased general condition
Depression
Loss of apetite
Nasal discharge, often thick and yellow, persistent coughing
Enlarged, tender lymph nodes between the palates

Sometimes the lymph nodes burst open and yellow pus comes out. Strangles can also have much milder symptoms and resemble a common cold, with fever, cough and runny nose.

Complications of strangles

Rarely (in about 1% of cases) abscesses will develop within other body organs which and can be fatal.
Another rare, but also potentially life threatening, complication of Strangles is ‘Purpura haemorrhagica’. This condition causes bleeding from the capillaries and fluid accumulation (oedema) in and around the limbs and the head. This accumulation of fluid can become so severe that it causes death.

Strangles risk factors

Young horses are particularly susceptible to infections, as their resistance is lower than that of adult horses. They should therefore be kept away from horses that travel a lot and are exposed to infection. Breeding mares and foals should also be protected from unnecessary infections

Environment

New horses always pose a risk of infection. It is therefore advisable to quarantine new horses before they are mixed with the other horses. A new horse should be kept separate from other horses for at least 14 days, preferably longer.
If the horse has not shown signs of any infectious disease during this time, there is little risk of it spreading the infection to the other horses. While the horse is in quarantine, it should have its temperature taken daily, as fever is an early sign of infection.
If you have had an infection in the stable, you should consult your vet about cleaning and disinfection. The bacteria can survive for several months if the temperature and humidity are right.
Clean and disinfect horseboxes that have been used to transport sick horses - otherwise they can be effective vectors of infection.

Travel

When you travel your horse to train or compete, you expose it to the risk of infection. To avoid your own horse spreading infection, you should refrain from travelling if you have or have had sick horses at home in the stable close to the competition. If you are unsure about what to do, you should discuss with your vet before travelling to the competition venue.

Vaccinate horses against strangles

Vaccination against strangles is recommended for horses that may be at risk of infection. The vaccine is given through two basic vaccinations, re-vaccination (booster) takes place after the veterinarian's recommendation based on the current risk of infection.
Speak to your vet to find out more about the vaccine against strangles.

Managing a horse with Strangles

Isolate

In case of suspected strangles, sick horses should be isolated from other horses as soon as possible to reduce the risk of further spread of the disease. The isolated horses should be cared for by a person who has no contact with other horses.
Contact a vet as soon as possible
The veterinarian will examine horses with symptoms and assess what action needs to be taken. If the vet also suspects strangles, local yards will be notified and the entire stable isolated.

Hygiene

Pay close attention to hygiene and minimise the number of people in contact with sick horses. It is important to wash hands thoroughly and to change shoes when leaving the yard. All clothing should also be changed before visiting other stables. Disinfect all equipment that has been in contact with sick horses. Horseboxes used to transport sick or suspected infected horses should also be thoroughly cleaned and disinfected.

Inform

Inform everyone who is in the stable and post clear information outside to avoid unauthorised visits to the stable.

Diagnosis

The vet will ask what symptoms the horse has had, whether other horses have fallen ill and where the infection is suspected to have come from. The horse's general condition is examined, the appearance of any nasal discharge is noted, the temperature is taken and the lymph nodes between the palates are examined.
The vet also listens to the heart and lungs and may try to provoke a cough by pressing the horse's throat.

If strangles is suspected, a sample is taken to culture the strangles bacterium, Streptococcus equi. The sample can be taken by swabbing the mucous membrane of the nasal cavity. Samples can also be taken further into the airways using fibre optics. Repeated sampling of several sick horses is often required to detect the bacterium, so a negative result is no guarantee that it is not strangles. Blood samples are often also taken to determine the severity of the infection.

Treatment

The mainstay of treatment for Strangles is supportive care. This involves treatment such as anti-inflammatory medication in order to treat the raised temperature and make horses feel well enough to eat. Feeding wet, sloppy food from the floor also makes it easier for infected horses to swallow and encourages the abscesses to drain. Hot compressing of the abscesses will also help to bring them to the surface, allowing them to rupture. Occasionally vets will treat infected horses with a course of antibiotics.

Rehabilitation and aftercare

A yard affected by strangles is usually isolated for at least 20 days after the last horse to show symptoms. During this period, no horses should be moved to or from the yard, with the exception being the movement of horses to isolation stables.
Once the last horse has recovered, it is important to clean and disinfect everything that has been in contact with sick horses. Otherwise, the quarantine bacteria can survive for months in the environment, if the conditions are right. It is important to clean all surfaces thoroughly, preferably with a pressure washer, before disinfecting, otherwise there is a risk that the bacteria will survive, encapsulated in dirt.
A horse that has had strangles should be started slowly afterwards. Consult your vet on what is appropriate.