Emergency: Guttural Pouch Mycosis
While sinus disease is not usually considered an emergency, a nose bleed should never be underestimated. It could be the sign of a rare, life-threatening fungal infection called guttural pouch mycosis.
A horse has two large guttural pouches, one on each side of the head, located high in the skull beneath the ear. They cool blood during exercise, particularly regulating the temperature of blood flow to the brain. The pouches are covered by a thin membrane, beneath which are important arterial veins and cranial nerves.
If a fungus has grown on an artery in a guttural pouch, it can cause fatal hemorrhaging due to arterial damage. If a horse has a nose bleed, a veterinarian usually first will check for a guttural pouch mycosis with an endoscope.
“It’s important to differentiate,” says Kenneth E. Sullins, DVM, MS, DACVS, a professor of surgery at Midwestern University’s College of Veterinary Medicine. “With guttural pouch mycosis, the bleeding will be bright red and profuse. It’s not something you’ll mix up with an ethmoid hematoma. Mycosis is an emergency.”
Guttural pouch mycosis is a serious fungal infection of blood vessels within pouches of the horse’s upper airway. This scope image shows an internal view of the mycosis.