Description

Because of the nature of its workings, a horse's guttural pouch may become a haven for bacteria, fungi, or other infectious agents that are inhaled or ingested by the horse. When these bacteria and fungi become trapped in the mucus that lines these pouches they cause infection and inflammation.

In a horse, the guttural pouches extend from the inner surface of each eardrum to the sides of pharynx, which is the opening in the back of the horse's mouth where nasal passages and the oral cavity join before separating into the trachea and the esophagus.

Although much research has been done on the role of the guttural pouch in horses' health, this unique structure remains somewhat of a mystery.

Indications are that these pouches serve several purposes in regulating temperature through air circulation with the cooling of the horse's brain as their key function. Fortunately, guttural pouch diseases do not occur frequently, but because of the potentially devastating effects, every horse owner should be knowledgeable about this part of the horse's body and its multiple functions.

Since the guttural pouches contain important nerves, arteries, and blood vessels, infection and tumors become serious problems when they occur.

Nerves in this area are responsible for crucial body functions, such as breathing, swallowing, and chewing.

Guttural pouch empyema, the presence of pus in the pouches caused by bacterial growth, often occurs following an infection of the pharynx. The most common organism involved is Streptococcus equi, but other organisms and fungi can cause erosion of the blood vessels and nerves leading to internal bleeding often revealed by intermittent bleeding from the nostril.

Symptoms

• External swelling of the pouch area
• Nasal discharge, often creamy in consistency and color and from one nostril
• Weight loss and debilitation
• Difficulty eating and swallowing because of nerve damage
• Drooping lip or ear or other facial abnormality if facial nerves are involved
• Intermittent bleeding, usually from one nostril as blood vessels and arteries become affected

Causes

With each breath or swallow a horse takes, bacteria, fungi, or other infectious agents have ready access to the guttural pouches. Most of the time the horse's immune system destroys these bacteria and fungi, but occasionally they survive and continue to grow by invading the warm, moist lining of the pouches.

When pus develops in the pouches, the condition is known as guttural pouch empyema and often occurs following an infection of the pharynx. Streptococcus equi is the most common organism involved, and the infection may follow a case of strangles. These bacteria cause a large amount of mucus that contains white blood cells, bacteria, and necrotic tissue from the guttural pouch.

This cottage cheese-like mass of debris is called chondroids. The first symptom is often a creamy discharge from one nostril when the horse lowers its head to graze.

The growth of fungi in the guttural pouch usually begins over one of the main arteries. A defect in the artery wall is usually present and allows the fungal infection to start. Aspergillus, Candida, Penicillium, and Mucor are the fungi most commonly found in the pouches. They grow naturally in hay, forage, and other parts of the horse's environment.

These fungi infections slowly erode the walls of the blood vessel and the horse will begin to bleed. If the bleeding is allowed to continue untreated, the blood vessel eventually will rupture and the horse will bleed to death.

Fungal damage may also affect the nerves in the walls of the pouches. When this occurs, horses may be unable to eat and swallow. They often lose tremendous amounts of weight, and eventually die.

Prevention

Keeping the horse's environment clean and free of breeding places for bacterial and fungal infestations is one way to keep guttural pouches from becoming infected.

Since these agents are always present in the horse's environment, it is nearly impossible to prevent all cases of guttural pouch infection, but knowing the symptoms and being aware of each horse's physical condition will allow the owner or trainer to catch the infections in the earliest stages and treat the horse effectively with positive results.

Treatment

Some cases of guttural pouch infection resolve themselves, but the majority of horses require treatment and therapy for a complete recovery. Aggressive flushing of the pouch by placing specialized catheters in the affected pouch and flushing large volumes of fluids repeatedly and with significant pressure will often remove the chondroids if they are caught in the early stages.

If the condition is chronic and severe, surgery may be necessary to drain the pouch. Technically, the surgery is difficult, but horses that receive the treatment before damage is done to the nerves and blood vessels respond favorably and often recover fully.

When the disease is caused by fungi in the pouch that affects the arteries, one possible treatment is restricting the blood flow through the artery, thereby curing the condition.

In advanced cases, a complicated surgery to ligate or tie off the blood vessels traveling through the pouch is necessary. Balloon catheters and surgical lasers are now being used in these procedures, but prognosis remains guarded in most cases.

Antifungal medication is administered for optimal recovery chances. If diagnosed early enough, the horse may fully recover with no permanent damage to crucial blood vessels and nerves.