Strangles in Horses

Strangles is a very common but unpleasant condition that can affect horses of all types. It is a highly contagious and potentially severe disease and all owners and handlers should be familiar with it.

Known scientifically as equine distemper, Strangles is caused by the bacterium Streptococcus equi and primarily targets the upper respiratory tract. Here’s a comprehensive look at what you need to know about Strangles, including its symptoms, prevention strategies, and treatment options.

Symptoms of Strangles

The incubation period for Strangles is typically between three to eight days and symptoms can vary in severity, so horses may not show all of these signs:

• Fever: One of the earliest and most common signs of Strangles is a sudden onset of fever, often rising above 39.5°C.
• Nasal Discharge: Initially clear, this discharge can quickly turn thick and yellowish as the infection progresses.
• Swollen Lymph Nodes: The lymph nodes under the jaw and in the throat area often become swollen and painful, potentially abscessing and draining pus.
• Difficulty Swallowing and Breathing: The swelling of the lymph nodes can cause significant discomfort and difficulty in swallowing and, in severe cases, may obstruct the airway.
• Loss of Appetite and Lethargy: Affected horses may exhibit a decreased appetite and general signs of discomfort and lethargy.

Diagnosis

Confirming a diagnosis of Strangles can be challenging.

A presumptive diagnosis may be made if horses exhibit contagious respiratory illness, high fevers, abscesses in the throat area, and rapid spread among animals in contact. However, not all cases can be definitively linked to Strangles, even when the clinical signs strongly suggest it, as the disease can be confused with viral respiratory infections.

Definitive diagnosis requires laboratory testing of nasal swabs or samples from draining abscesses. In some cases, endoscopy is used to examine the throat and flush the guttural pouches, a valuable method for identifying carrier horses, with around 20% of all infected horses becoming asymptomatic carriers.

Stopping the spread of Strangles

Once Strangles appears in a stable yard, it is extremely difficult to stop it spreading. Unlike influenza, Strangles is not airborne and it doesn’t spread over long distances without direct contact.  

It spreads primarily through direct contact between horses or via contaminated objects, such as when horses rub noses or share drinking troughs. Bacteria can be transferred through contaminated clothing, buckets, tack, and other equipment and can survive in the environment for several weeks, making dirty stables a potential source of infection.

Horses can shed bacteria while incubating the disease, a few days before showing symptoms, and for several weeks after recovery. Some horses become “carriers,” harbouring the bacteria in their respiratory tract, and may shed the infection for years without showing any signs of illness. Around 20% of all infected horses become these asymptomatic carriers.

However, not all horses in the same group will necessarily catch the disease, similar to how not every member of a family gets the same cold.

Prevention of Strangles

Preventing Strangles involves stringent biosecurity measures and vaccination. Here are some key steps to minimise the risk of infection:

• Hygiene Practices: Poor hygiene among handlers is a key issue in the spread of Strangles. Regularly disinfect stables, equipment, and transportation vehicles. Ensure that each horse has its own set of grooming tools and feeding buckets, which should be routinely cleaned and disinfected.
• Quarantine New Arrivals: Isolate new horses for at least two weeks and monitor them for any signs of illness before allowing them to mingle with other horses.
• Vaccination: There are vaccines available that can help reduce the severity and spread of Strangles. Your Stride Vet can help you set up an appropriate vaccination schedule.
• Limit Stress: Stress can weaken a horse’s immune system, making it more susceptible to infections. Maintain a calm and stable environment for your horses.
• Early Detection: Regularly monitor your horses for any signs of illness and act quickly to isolate it and contact your vet if symptoms of Strangles appear.

Treatment of Strangles

If a horse contracts Strangles, prompt veterinary care is essential. Treatment of an affected horse typically involves:

• Isolate from other horses.
• Keep the horse comfortable with good nursing care to encourage eating and drinking.
• Place hay and feed on the ground to help drain nasal discharges.
• Provide soft, moist, palatable food that is easier to swallow with a sore throat; add a little salt to encourage drinking.
• Administer Phenylbutazone (“bute”) or other medication as prescribed by your vet to reduce fever, throat soreness, and swelling that makes swallowing difficult.
• Apply hot packs to firm abscesses to help them soften and burst. This can relieve pressure and promote healing.
• A vet can only lance an abscess when it’s nearly ready to burst, feeling soft and fluid-filled.
• Clip or trim hair over an abscess to make cleaning easier once it bursts.
• Flush draining abscesses daily with a very dilute antiseptic solution (Hibiscrub at a 1:50 ratio with water) or salt water.
• Protect healthy skin around the draining abscess by cleaning regularly and applying Vaseline around (but not in) the wound.
• Turnout is fine if pasture contamination or contact with horses in neighbouring fields isn’t a concern, as fresh air can benefit the horse but may contaminate grazing areas.

The use of antibiotics in treating Strangles can be controversial. They may be beneficial in the later stages once abscesses have been lanced and drained, or for treatment of an asymptomatic carrier via endoscopy.

Recovery and Aftercare

Recovery from Strangles can take several weeks, during which continued supportive care and monitoring are crucial. Once recovered, horses can still shed the bacteria for up to six weeks, so extended isolation and gradual reintroduction to the herd are recommended.

Regular veterinary check-ups will ensure that the horse is fully recovered and free from any potential complications, such as “bastard Strangles,” where abscesses form in other parts of the body, or chronic carrier states.

Conclusion

Strangles is a serious condition that requires vigilant prevention and prompt treatment. By recognising the symptoms early, implementing strong biosecurity measures, and working closely with your Stride vet, you can significantly reduce the impact of this disease on your horse.

Stay informed, stay vigilant, and keep your horses safe from Strangles.