Guttural Pouch Infections

Lauren Alderman, DVM, CVA, CVSMT
Edits and contributions made by: Kimberly Allshouse, DVM

The horse’s guttural pouches are a pair of air-filled sacs in the throatlatch region. The guttural pouches are an extension of the eustachian tubes, which in humans are tiny tubes connecting the middle ear to the back of the throat. In horses, guttural pouches are lined with a thin membrane and surrounded by several very important structures, including the internal carotid artery and cranial nerves that control facial expression, swallowing, and upper respiratory tract function. A long, thin stylohyoid bone divides each guttural pouch into lateral and medial compartments.   

Guttural pouches can harbor various bacterial and fungal infections.  Guttural pouch empyema, or pus in the guttural pouches, often stems from streptococcal infections. In a horse infected with Streptococcus equi subspecies equi (strangles), for instance, an abscessed retropharyngeal lymph node can rupture and drain pus into the guttural pouches. Signs of guttural pouch empyema might include fever, depression, nasal discharge, and painful throatlatch swelling. Occasionally, inflammation and infection within the pouches can impair the cranial nerves alongside them, causing difficulty swallowing, noisy breathing, or impaired function of the muscles involved in facial expression.  

Pus that remains in the guttural pouches for a long period can become inspissated, or dry out, and form chondroids. These firm balls of pus can be difficult to remove from the guttural pouches and can cause a horse that appears healthy to continuously shed infectious bacteria.  Horses can have guttural pouch chondroids without obvious clinical signs. In these cases, horses may be chronically shedding the bacteria and infecting other horses without outwardly appearing sick themselves.  

Veterinarians typically diagnose guttural pouch empyema and chondroids with endoscopy. This procedure involves the insertion of a thin, flexible camera into the guttural pouches via the nasal cavity. Radiographs can also reveal fluid or chondroids in the guttural pouches, but endoscopy provides a more definitive diagnosis. To rule out that a horse is shedding the bacteria that cause strangles, a fluid sample from the guttural pouches can be cultured and submitted for PCR testing.  

Prognosis for guttural pouch empyema is good with medical treatment, which often involves daily lavage (flushing) of the infected pouches and antibiotic therapy. Systemically ill horses might also require supportive care, including non-steroidal anti-inflammatory drugs to help control fever and malaise. Some horses might need surgery to remove large chondroids, although veterinarians often avoid this if possible due to the risk of damaging surrounding nerves and subsequent impaired respiratory and swallowing function. If left untreated, the infection can cause airway obstruction and asphyxiation, so it is important to contact your veterinarian with any concerns. Streptococcus equi ssp equi infections must be reported to the state veterinarian in certain states.  If you have a suspicion that your horse may have a respiratory infection, please do not transport your horse until they have been seen by a veterinarian.  

Another type of guttural pouch infection is guttural pouch mycosis, or fungal infection within the guttural pouches.  Guttural pouch mycosis is rare and potentially life-threatening. Although fungal plaques can form anywhere within the guttural pouches, they tend to form over the internal carotid artery due to the excellent blood flow in this location. Erosion of a fungal plaque through the wall of the internal carotid artery can lead to sudden, severe, and potentially fatal epistaxis (nosebleed).  

Clinical signs of guttural pouch mycosis can be subtle. Veterinarians might suspect the condition in a horse with intermittent and recurrent mild nosebleeds, noisy breathing, facial asymmetry, or dysphagia (difficulty swallowing), which can sometimes lead to unexplained episodes of choke. Veterinarians typically diagnose guttural pouch mycosis using endoscopy.  

The prognosis for horses with guttural pouch mycosis varies depending on the extent of disease and the clinical signs present. Horses developing sudden, severe hemorrhage might need blood transfusions and emergent surgical intervention. Medical treatment of guttural pouch mycosis, involving lavage and antifungal medication, can be successful but often takes months and the risk of sudden hemorrhage remains as long as a fungal plaque is active. Surgical treatment involves ligating (tying off) or otherwise blocking blood flow to the segment of internal carotid artery underlying the fungal plaque. If there are neurologic signs present including dysphagia, the prognosis is worse than in an uncomplicated case without neurologic deficits.   

Other guttural pouch conditions can develop in horses, as well. Guttural pouch tympany, or entrapment of excessive air within one or both guttural pouches, can affect young horses. Cancerous masses can form near or within the guttural pouches in any age animal, as can hyoid problems, such as THO (Temporohyoid Osteoarthropathy).  THO or the presence of a mass can result in impingement on the adjacent cranial nerves, affecting their function.  

Discuss any concerning changes in your horse with your veterinarian, who can help determine the best course of action for diagnosis and treatment.  

Article provided by AAEP Media Partner, The Horse.