Guttural pouch mycosis is a fungal infection of the guttural pouch, an outpouching of the Eustachian tube that connects the ears to the nose and mouth and helps to regulate air pressure. 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.

Last full review/revision July 2011 by Bonnie R. Rush, DVM, MS, DACVIM; Neil W. Dyer, DVM, MS, DACVP; Joe Hauptman, DVM, MS, DACVS; Ned F. Kuehn, DVM, MS, DACVIM; Stuart M. Taylor, PhD, BVMS, MRCVS, DECVP; Wendy E. Vaala, VMD, DACVIM; Maureen H. Milne, BVMS, MVM, DCHP, MRCVS