Guttural Pouch Disease in Horses
The guttural pouch is a structure found only in equine species. It is an outpouching of the Eustachian tube, the tube that connects the ears to the nose and mouth and helps to regulate air pressure.
Guttural pouch empyema is a condition in which pus- and bacteria-containing secretions accumulate in the guttural pouch.
The condition usually develops after a bacterial infection of the upper respiratory tract. Signs include intermittent nasal discharge that contains pus, painful swelling, and in severe cases, stiff head carriage and noisy breathing. Fever, depression, and loss of appetite may or may not be seen. A diagnosis can often be made after endoscopic examination of the guttural pouch. Guttural pouch empyema should be considered a Streptococcus equi equi infection (the cause of strangles) until proven otherwise, and isolation or quarantine procedures should be instituted in affected horses until the bacterial culture results are obtained.
Antibiotic therapy alone will not resolve the infection; the guttural pouch must be rinsed out by lavage. Guttural pouch empyema may compress the throat and produce upper airway obstruction. If this occurs, a tube through the trachea (tracheotomy) may be necessary to provide a temporary alternative airway. If guttural pouch empyema is not treated, the material in the pouch continues to provide a source of bacteria for infection.
Guttural pouch mycosis is a fungal infection of the guttural pouch. Aspergillus species of fungus are common causes of these infections, although other species are sometimes identified. The infection is usually seen in mature horses that are stabled. Guttural pouch mycosis causes damage to the cranial nerves and to the arteries found in the lining of the guttural pouch.
The most common sign of infection is bleeding from the nose due to arterial damage. The bleeding occurs without any obvious cause and is often severe. Difficulty swallowing is another common sign. Horses that have difficulty swallowing often have a poor outlook. Other signs include respiratory distress, extended or low carriage of the head, and fluid buildup and swelling of the head. The diagnosis is based on the history, signs, and examination of the guttural pouch with an endoscope.
Treatment can be difficult, and it is not always effective. Antifungal drugs that are infused directly into the guttural pouch are the usual treatment for guttural pouch mycosis. If damage to the arteries has occurred, it may be necessary to perform surgery to close the affected blood vessel. This can help prevent a fatal hemorrhage. Nerve function may or may not return after the infection resolves.
Guttural pouch tympany occurs when the guttural pouch becomes abnormally filled with air, causing nonpainful swelling just behind the jaw. The condition occurs in young horses (from birth to 1 year of age) and is more common in fillies than in colts. It may be caused by inflammation or by a congenital (present at birth) defect that allows air to enter the pouch but prevents it from returning to the pharynx.
Often, the swelling is the only noticeable sign; it may occur on one or both sides of the head. Other signs may include difficulty breathing, nasal discharge, and carrying the head in an extended position. The diagnosis is based on the signs and x‑rays of the skull.
Treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) and appropriate antibiotics is successful in most horses in which inflammation is the cause. If tympany is due to a congenital defect, surgery is required to provide a route for the air to be expelled from the affected guttural pouch. The outlook for recovery is good in most cases.
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