What are Guttural Pouch Mycosis?
There appears to be no age, gender, or breed predisposition to this disease; however, there is an increase in cases in animals who are stabled during the warmer months of the year.
As this condition often worsens over time as the disease progresses, and life threatening complications can occur it is vital you contact your veterinarian if symptoms occur.
Guttural pouch mycosis is a rare disease that affects horses. This is caused by a fungal infection of the guttural pouch. This condition can be potentially life-threatening due to the risk of spontaneous hemorrhage. Although the most common clinical sign is bleeding from the nostrils, other symptoms such as facial paralysis due to damage to the cranial nerves, colic, sweating, and shivering may be seen.
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Symptoms of Guttural Pouch Mycosis in Horses
Unilateral bleeding from the nose at rest is the most common symptom of this disease, this may be in small drops or profuse amounts. In some cases, dysphagia (difficulty swallowing) and difficulty breathing are seen. Unfortunately, the presence of dysphagia often indicates a poor prognosis. Other symptoms that may be seen are:
- Difficulty swallowing with food sometimes appearing at the nostrils
- Facial nerve paralysis
- Swelling of the neck
- Decreased performance or exercise tolerance
- Shaking of the head
- Dark, old blood may also be seen at the nostrils
- In some cases, the only symptoms may be sudden hemorrhage from the nasal passages
Causes of Guttural Pouch Mycosis in Horses
Guttural pouch mycosis is a fungal infection that affects horses. Guttural pouches are unique to few species of animals, including the horse. These structures are large air filled sacs, positioned on either side of the neck, below the ear of the horse. They are lined with a thin membrane, which separates them from nerves and and arteries. Due to the placement of these pouches, trauma to these structures can cause severe consequences, leading to life threatening hemorrhage in some cases.
Guttural pouch mycosis causes the pouch to become infected, resulting in necrotizing, inflamed, and thickened tissue. This disease causes a plaque to form over the roof of the pouch. This often causes the invasion of major arteries and nerves at the base of the skull, hence the life threatening hemorrhage and severe nerve damage occurring.
The most common fungus seen is Aspergillosis. Aspergillosis is seen worldwide in most domestic animals and commonly responsible for respiratory infections, particularly in birds.
This fungus is found in horse bedding that has had urine contamination and water. It is thought that it enters the horse’s body through the throat or trauma to the surrounding tissue.
Diagnosis of Guttural Pouch Mycosis in Horses
Your veterinarian will perform a full clinical examination on your horse and discuss their recent behaviour and health with you. If your veterinarian suspects guttural pouch mycosis they may perform an endoscopy examination. Your horse will require sedation for this procedure, the endoscope will then be passed through the nose into the guttural pouch and carefully rotated to allow your veterinarian to carefully examine the pouch.
Radiography may also be used, particularly if your horse is suffering from nasal hemorrhage that contraindicates endoscopy examination. Your horse will be sedated and radiographs of the laryngeal region taken. Irregular shaping or masses visible in the radiographs may indicate disease.
Treatment of Guttural Pouch Mycosis in Horses
Treatment of this disease will often require referral to a specialised hospital for surgery. Your horse will require general anesthetic for this procedure. As the main risk with this condition is hemorrhage, the aim of surgery is to find the affected artery that is feeding the mycotic plaque and occlude it using non-absorbable suture material. This results in clot formation at the vascular lesion. In some cases, plaque removal will also be performed. Your horse will require general anaesthetic for this procedure.
Another procedure that may be considered is the use of latex balloons and coil embolization to occlude the arteries. Antimicrobial treatment may also be considered by your veterinarian.
Recovery of Guttural Pouch Mycosis in Horses
In horses that receive successful surgical treatment the prognosis is good. Complications from surgery include hemorrhage prior to or during surgery, postoperative retrograde arterial flow or failure to litigate the correct vessel leading to hemorrhage, trauma to the cranial nerve resulting in facial paralysis, and infection of the surgical site.
Your horse may require hospitalisation following surgery and be monitored closely for signs of infection or complication. During recovery, assisted feeding and intensive nursing may also be required.
Unfortunately, in horses that have extensive plaque or hemorrhage prior to treatment or suffer from severe nerve damage affecting respiration and swallowing, the prognosis is guarded.