Strangles in Horses: What It Is, Symptoms, and Treatment Options

Strangles in horses is a serious respiratory disease that can cause swollen lymph nodes in a horse. It’s important to understand the risks associated with equine strangles and how you can protect your horse.

What Is Strangles in Horses?

Strangles is a highly contagious disease common in horses, caused by the bacterium Streptococcus equi.

Strangles in horses is observed worldwide and can affect any horse of any breed or age, although young to middle-aged horses in frequent contact with others seem to be most affected.

Symptoms of Strangles in Horses

If you notice any of the following signs, isolate your horse from others until your veterinarian can perform a full examination to prevent potential spread of disease.

• Nasal discharge

• Fever

• Swollen lymph nodes under the jaw, which may or may not be open/ draining

• Lethargy

• Decreased appetite

Fever is typically the first clinical sign to appear in cases of equine strangles, usually within three days after initial exposure to the bacteria. Nasal discharge and swollen lymph nodes follow a few days later.

Lymph node abscesses may break open in one to four weeks and have a thick discharge. A horse’s recovery is expedited once the abscess ruptures naturally and the bacteria can drain.

Symptoms of Bastard Strangles

In rare cases, abscesses may form in areas beyond the jaw. This is known as “bastard strangles” and can affect lymph nodes in the abdomen or brain.

If this occurs, you may also see signs of colic or neurological abnormalities such as circling, head pressing, and ataxia (weak or “drunk” hind end). 

How Do Horses Get Strangles?

Strangles in horses is easily transmittable through nose-to-nose contact, sharing water or feed buckets, or use of contaminated equipment or grooming tools.

Once inhaled or ingested, the bacteria cross the mucous membrane barrier and enter the bloodstream, traveling to the lymph nodes—its breeding ground.

As the bacteria begins to multiply and take up increasing amounts of space, it causes abscesses within the horse’s lymph nodes. They will slowly enlarge, which can put pressure on or compress the trachea.

Decreased airway space can lead to difficulty breathing, so you may notice your horse stretching their neck out or breathing abnormally. This is where equine strangles gets its name because the horse can sound like or seem like they’re being strangled.

How Veterinarians Diagnose Strangles in Horses

Strangles may be suspected based on a horse’s history and clinical signs of swollen lymph nodes, fever, and nasal discharge; however, definitive diagnosis should be made to ensure proper treatment plans.

In addition to a thorough physical examination, your veterinarian may perform one of the following tests:

• Nasal swab: This is the easiest route of sampling. A culture swab is passed along the inside of the nostril to pick up any bacteria present. If there is not a large amount of nasal discharge or it’s early in the disease process, a false negative result may occur.

• Nasal wash or guttural pouch flush: For this procedure, a small tube is passed either further up the nasal passages or into one of the guttural pouches (typically using video guidance). Saline is passed through the tube and will come back out through the nose to be caught.

• Fine needle aspiration of a swollen or abscessed lymph node: This test can help determine what bacteria is present in the enlarged lymph node.

A culture test typically takes about two to three days and is relatively low in cost. However, early in the disease process, false negatives can occur if the horse is not yet shedding the bacteria in their nasal discharge.

PCR (polymerase chain reaction) testing is faster and more sensitive; the only potential downfall to this test is that it is unable to differentiate between active/live versus dead bacteria.

Strangles in Horses Treatment

Treatment of strangles is typically aimed at supportive care, such as making sure your horse continues to eat, stays hydrated, and doesn’t develop any further systemic issues.

Banamine, an anti-inflammatory, is commonly used to help keep fevers down and aid with appetite.

Your horse will be on stall rest in quarantine to allow them time to heal and to prevent spreading bacteria to other horses nearby.

In severe cases of respiratory distress, if the lymph nodes are impeding air flow, a temporary tracheostomy (breathing tube placed in trachea) may be necessary.

Recovery is much more rapid after the abscesses have opened on their own and are allowed to drain. Your veterinarian may have you apply a warm compress daily to help speed that process.

Once the abscess is opened, it will be cleaned or gently flushed with sterile saline under the direction of a veterinarian to help drain the bacteria and prevent spreading.

Recovery and Management of Strangles in Horses

Recovery of equine strangles is relatively straightforward after abscesses rupture, drain, and heal.

While your horse may be looking and feeling much better, they can still actively shed bacteria for up to six weeks. To prevent spreading strangles, keep your horse isolated until guttural pouch sampling tests negative and your vet confirms they’re strangles-free.

Your horse should rest during this time to allow for full healing and minimization of respiratory distress. Light work can resume once draining sites have healed, but tack and grooming equipment should still not be shared.

Horses recovering from strangles should be cared for last after all healthy horses are cared for during the day.

Risk of Purpura Hemorrhagica

Occasionally, strangles can lead to a secondary disease called purpura hemorrhagica (PH). This causes inflammation and swelling of blood vessels.

Clinical signs of PH include swelling of the head, edema of the legs and abdomen, and red spots of the mucous membranes and gums.

Luckily, PH is not contagious like strangles, and with treatment—typically antibiotics and steroids—most horses recover quickly.

How To Prevent Strangles in Horses

Strangles Vaccine for Horses

Young and middle-aged horses who board or travel often for shows and events may benefit from the strangles vaccine, as they’re at higher risk of exposure.

There is both an intramuscular (IM) and intranasal vaccine; these should not be administered in the face of an outbreak when there is potential exposure.

In rare cases, the IM vaccine can cause abscesses as a side effect, so discuss with your veterinarian whether this vaccine is right for your horse.

The intranasal vaccine generally has lower risks of side effects; you may see some temporary upper respiratory signs such as a runny nose, but this is non-contagious.

A titer test can determine a horse’s antibody levels to see if yearly re-vaccination is necessary; however, these tests often cost much more than the vaccine itself.

Discuss with your primary veterinarian to decide which vaccine protocol would be best for your horse.

Quarantining Horses and Cleaning Measures

In the case of a strangles outbreak in your barn, strict cleaning and quarantine procedures can help prevent your horse from contracting the disease. The following practices can be implemented:

• Take your horse’s temperature twice daily. If it rises above 101.5 F, your horse should be quarantined, monitored for nasal discharge and swollen lymph nodes, and examined by your veterinarian.

• Keep your horse’s water bucket clean, and don’t allow sharing with any other horses.

• Prevent nose-to-nose contact with other horses in the barn.

• Always feed, exercise, and groom healthy horses before quarantined horses. Do not share equipment, and do not interact with healthy animals again unless you shower and change clothes after you’ve handled a horse in quarantine.

• Thoroughly clean any materials used on a sick horse after use. Completely empty and spray down the stall after the horse is removed from quarantine, machine wash any nylon halters used, and disinfect grooming materials.