Strangles

Strangles

Streptococcus equi (S. Equi), also known as Equine Distemper, is a highly contagious, debilitating disease.  It has the ability to quickly pass through a stable or farm and the after effects can be long withstanding.

Because strangles is so contagious, it is important for horse owners to understand mechanisms of this disease so it may be diagnosed and treated before passing through an entire herd.

S. Equi bacteria can survive an unknown length of time and is spread via pus, draining lymph nodes, coughing, direct nose-to-nose contact and even by flies. It has the ability to survive an unknown length of time.

While infection most commonly occurs in horses which travel frequently or in large herds with a high rate of new horses rotating in and out, it can be picked up by a single trip off the farm at any place horses congregate such as a weekend trail ride or small playday.

Once the horse picks up the bacteria, it enters into regional lymph nodes. Lymph nodes become enlarged and can lead to the trachea or pharynx becoming compressed, causing labored breathing, thus the term “strangles.” Swallowing also becomes painful.

There is a three to eight day incubation period in which the abscesses form. Once the abscesses rupture and drain, there is a two to three week recovery period. Typically, the horse will remain infective for weeks, and a small number can be infectious for years.

The most common signs include fever, nasal discharge (which may be green, yellow or white), loss of appetite, anorexia, depression, cough and swellings, usually on the underside of the jaw. This swelling is the result of abscess formations on the lymph nodes due to pus accumulation.

Abscesses on lymph nodes in the throat area can burst into the guttural pouches, resulting in the nasal discharge. This pus, which is thick and yellow, is contaminated and spreads the disease.

The horse may stretch out his head and neck to relieve pressure caused by the swollen lymph nodes.

There are additional forms of strangles which can afflict the horse. When lymph nodes outside the head and neck are affected (i.e. chest or abdomen), the form is referred to as metastatic or “bastard” strangles. This may be seen in horses which have an abbreviated illness, have partial immunity to this disease, or if a less virulent strain has been contracted (catarrhal form), with minor or no lymph node abscesses seen. 

In addition, strangles can also cause immune complexes which can lead to blood vessel damage (called purpura hemorrhagica). Horses with this may have limb and head swelling, circulatory failure and death.

Severe cases of S. Equi may result in death or require euthanasia. It should be noted that while death from strangles is rare, higher incidences of death are seen in horses with cases of bastard strangles.

All ages are susceptible, however, foals and yearlings are most likely to be affected due to a developing immune response. Not all horses which are exposed become infected. This depends on the amount of bacteria the horse comes in contact with, his immune status and other conditions (stress, nutrition, pre-existing illnesses).

If strangles is suspected, call your vet. The sooner diagnosed, the sooner measures may be taken to prevent further spread through the herd. Diagnosis is made via clinical presentation and culturing the pus. Horses which chronically shed the bacteria are more difficult to diagnose.

The vet will tailor a treatment plan specific to the individual horse. Treatment consists of Bute or Banamine for fever, antibiotics, flushing the abscess with Betadine solution, and keeping the area clean. The abscesses may be lanced or a tracheostomy performed to facilitate better breathing. Guttaral pouches may be flushed to promote drainage of the pus.

Prevention is, of course, key. Do not allow your horse to nose or come in contact with horses outside of his normal herd. Incoming horses should be isolated 2-3 weeks before introducing into the herd. Temperatures should be taken at least once daily. Vaccinations are available, but there are pros and cons for their use. Infected horses should be isolated for six to eight weeks.

Most horses recover within seven to 10 days from onset. There are usually no long term after effects. Complications can occur, and they include myocarditis (inflammation of the heart muscle), cellulitis, roaring, anemia, and pus filled guttural pouches.

Management is crucial to control the effects of S. Equi. Stringent protocols should be implemented to prevent cross-contamination of tack, buckets, water troughs, brushes and bedding. If possible, affected horses should be housed in a stall with concrete walls and floor for easier disinfecting. Keep in mind S. Equi can survive for several weeks and ultraviolet light can kill S. Equi bacterium.

There is a test available to determine carriers of strangles.