Strangles in horses

Strangles is a highly contagious disease in horses in which inflammation occurs in the lymph nodes. These inflammations are caused by the strangles bacterium, Streptococcus equi. Strangles is common in young horses, but can occur at any age. Often, Strangles is dismissed as a harmless disease, but it can be fatal. Around 1-2% of horses die from Strangles.

What is strangles?

The strangles bacterium multiplies in the lymph nodes, causing inflammation. This results in painful abscesses in the throat area, which are very visible near the horse's jaw. The abscesses eventually burst open, allowing pus and mucus to come out, often through the nostrils. This form of strangles often offers good recovery possibilities for the horse. However, sometimes abscesses can develop in other areas of the body, indicating that the bacterium has spread through the bloodstream; this is called Bastard Strangles. Abscesses can form in the abdominal cavity, organs, and/or muscles. Bastard Strangles is usually fatal in most cases.

Strangles has characteristic symptoms. Around 3-14 days after infection, the first signs of illness appear. Typically, symptoms start with fever and white or clear nasal discharge. After a few days, horses become lethargic, eat poorly, and develop a pus-like nasal discharge. The characteristic strangles bumps form under the jaw due to inflamed lymph nodes. It is important to note that the swelling under the jaw is not always visible.

Due to pain, horses with strangles may have difficulty swallowing, causing food to come back up through the nose. These horses often keep their necks extended due to the pain. The abscesses often compress the throat, making breathing more difficult; in severe cases, the horse may even choke. Within a few weeks, the inflamed lymph nodes break through to the outside or the oral cavity. Often, horses feel better and show fewer signs of illness at this point. With Bastard Strangles, the disease progression varies. One day, the horse may have less fever than on another, but these horses often lose weight quickly and develop other symptoms like colic and diarrhea.

Strangles is highly contagious

The pus is highly contagious and full of the strangles bacterium. Infection mainly occurs through direct contact between horse noses or via indirect contact (water troughs, clothing, fencing, etc). Therefore, it is important to isolate infected animals to prevent direct transmission. People caring for infected animals should wash and change before attending to other horses. Strangles does not spread over long distances through the air.

Under ideal conditions, the strangles bacterium can remain infectious for up to 2 months. However, it is sensitive to disinfection, so thorough cleaning of equipment is a good step in controlling a strangles outbreak in the stable.

In the Netherlands, strangles is not a notifiable disease, meaning you do not have to report it officially if your horse or stable is affected. However, it is advisable to inform others so that surrounding horse owners can take preventive measures.

How is strangles diagnosed?

Usually, the symptoms are clear enough for the veterinarian to diagnose strangles based on clinical signs. If this is not the case, the vet can take a nasal swab and perform a PCR test to determine the presence of the strangles bacterium. A horse can become a carrier of strangles, with around 10% of infected horses becoming carriers. These horses remain a source of infection for other horses, but with the proper treatment by the vet, they no longer pose a risk.

How do you treat a horse with strangles?

Antibiotics should not be given for strangles, except in exceptional cases. Antibiotics inhibit the maturation of abscesses, and in most cases, it is better to let the abscesses mature and burst open.

A horse with strangles should rest. Motivating the abscesses to burst open by shaving them and applying laurel or drawing salve can be helpful. After the abscesses burst open, the cavities should be flushed at least once per day. Due to pain while swallowing, horses may eat and drink less. If eating is difficult, it is advisable to provide easily consumable food at chest height.

Horses with Bastard Strangles should receive antibiotics. You do not want the abscesses to burst in other parts of the body, so these horses often require prolonged antibiotic treatment.