Battling Guttural Pouch Mycosis: A First-Hand Account

by | 02.07.2018 | 5:54pm
Foozie in healthier days, shown with his friend, a wolf named Navarre

Foozie is my farm clown. The 17.2-hand Thoroughbred gelding likes to steal hats and lead his pasture mates around by the halter. As gentle as he is big, Foozie also can be a handful at times. So when he stopped his playful antics, I knew something must be wrong.

Foozie became lethargic, just moseying up to his feed tub instead of his usual high-spirited race to the barn. He nosed around in his feed and dropped grain from his mouth when he chewed. Thinking he must have a bad tooth, I called my farm veterinarian.

The dental examination revealed no problems, as did the rest of the physical examination. Blood work showed an increase in fibrinogen, but nothing else remarkable. Yet the stoic Foozie definitely was sick. I could see it in his face.

I loaded Foozie on the trailer and took him to Dr. Nathan Slovis, director of the McGee Medicine Center at Hagyard Equine Medical Institute. There, Slovis inserted an endoscope in each of Foozie's nostrils to examine his guttural pouches. He discovered a profound fungal infection (mycosis) in Foozie's left guttural pouch, the worst he had ever seen. The majority of the guttural pouch was black with fungus.

“An upper airway scope revealed a very large soft mass with plaques attached to the stylohyoid bone and covering a large area of the medial and lateral compartments of the left guttural pouch,” Slovis reported.

My big clown was seriously ill, and I was in danger of losing him.

The horse has a guttural pouch on each side of its throat that is a diverticulum of the Eustachian tube that connects the nasopharynx to the middle ear. Important arteries and nerves pass through the guttural pouch. Without immediate and prolonged, intensive treatment, a horse with guttural pouch mycosis suddenly may bleed to death from the nostril when the disease erodes an artery. Damage to the cranial nerves could render the horse unable to swallow or breath, also causing death.

In Foozie's case, the mycosis infection was centered over his stylohyoid bone, where the tongue is anchored. This accounted for his reluctance to eat and dropping grain as he attempted to chew.

Interestingly, Foozie's sire died 20 years earlier from a massive hemorrhage of the carotid artery caused by a guttural pouch mycosis. He showed no symptoms before the fatal event. These are the only two horses I've had with this condition, and no common denominators existed other than heredity that may have predisposed them to the disease. Curiously, a week before Foozie became lethargic, I noticed a smear of blood on the side of the barn, apparently from a horse wiping its nose bleed. This was the red flag that alerted me this could be something serious.

Treatment

Using the endoscope to deliver treatment, Slovis lavaged the mass and guttural pouch with diluted Betadine,  then applied antifungal Clotrimazole ointment all over the mass. He gave Foozie a dose of the anti-inflammatory Banamine to make him more comfortable before sending the horse home.

Images from the veterinarian's exam of Foozie, who was diagnosed with guttural pouch mycosis

Slovis discussed several other methods of treatment with me: Foozie could be put on systemic antifungal medication plus sodium iodide for an extended period of time at $30/day. Another option was to place a catheter in his guttural pouch so I could treat him at home daily, but this required assistance to treat him and maintenance of the catheter. Finally, there was a surgical option, a coil embolization:

“The artery that runs in the guttural pouch and is at close risk of being disturbed by the mass and causing bleeding can be occluded via a surgical procedure,” Slovis said. “He would need to be anesthetized for this procedure and likely the mass should still be treated following surgery.”

Because the fungal plaque was not adjacent to one of the major arteries, we decided to repeat the lavage and Clotrimazole application twice a week for the next six weeks. To make eating more comfortable for Foozie, Slovis instructed me to feed him an equine senior feed softened with water into a slurry that required little chewing. He also recommended adding corn oil or Healthy Weight by Platinum Performance to the slurry to prevent weight loss

Slovis is certified in hyperbaric oxygen therapy, which is especially effective for fungal infections. He suggested the horse have 10 treatments in the hyperbaric chamber. I sent Foozie to KESMARC in Versailles, Ky., for the next six weeks, where Kirsten Johnson managed his hyperbaric oxygen sessions and other treatment.

Foozie responded exceptionally well to the combined antifungal and hyperbaric oxygen treatments, with Slovis reporting a 15 percent improvement after the first week. After the third week of treatment, Foozie's mycosis was 80 percent resolved. Treatments continued for the full six weeks to assure his complete recovery.

What causes guttural pouch mycosis?

The fungal genus (mold) most commonly responsible for guttural pouch mycosis, aspergillus spp., is prevalent in the environment. It includes more than 185 species, found in the soil, plant debris, and the air we breathe, both indoors and outside. Scientists are unsure why this fungus becomes aggressive and attacks the membranes of the guttural pouch. A combination of environmental conditions in the pasture, namely rain and heat, are thought to nurture the mold into an aggressive state.

With no definitive cause identified, veterinarians can only speculate how to lessen the chances your horse will develop guttural pouch mycosis: Keep stalls clean and dry. Be sure to clean out the corners of the horse's stall where molds and fungi might accumulate. Keep the barn well ventilated, and feed good-quality hay that is free from mold and fungus.

For those horsemen who want to go one step further, they can include endoscopy of the guttural pouches and upper airway in the horse's annual checkup.

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