THE MERCK VETERINARY MANUAL
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Overview of Pharyngitis

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Pharyngitis is an inflammatory condition of the walls of the oro- or nasopharynx. Pharyngitis may develop secondary to viral or bacterial infections of the upper respiratory tract, eg, strangles in horses and distemper in dogs.

In most species, a common pharynx is present at times other than deglutition. The unique caudal pharyngeal-laryngeal anatomy of horses shows complete separation of the pharynx into two components, the nasopharynx and the oropharynx. (Also see Pharyngeal Lymphoid Hyperplasia in Horses.)

Animals affected with pharyngitis have a normal desire to eat and drink but may have difficulty swallowing and appear dysphagic. Animals with secondary peripharyngeal cellulitis and abscessation may be acutely dyspneic secondary to pharyngeal obstruction. For example, foals affected with suppurative pharyngitis secondary to abscessation of the retropharyngeal lymph nodes can become acutely dyspneic and require an emergency tracheotomy.

The diagnosis of pharyngitis can be made with a complete physical examination, radiography of the skull, endoscopic evaluation of the pharynx, and microbial cultures of draining abscesses or nasopharyngeal swabs for viral isolation. In small animals, oral pain and resistance to having the mouth opened may indicate retropharyngeal abscessation and the presence of a penetrating foreign body or oral or tonsillar neoplasia. Abnormal pharyngeal tissue should be biopsied and submitted for histopathology to exclude pharyngeal neoplasia. In small animals, oral examination and/or endoscopic examination is the best diagnostic tool for pharyngitis. In large animals, the diagnosis of pharyngitis is easily made by endoscopic examination of the upper respiratory tract.

Bacterial pharyngitis should be treated with systemic antimicrobials based on microbial culture and sensitivity testing. Abscesses should be drained and lavaged when appropriate. Viral-induced pharyngitis should be managed with antimicrobials to prevent secondary bacterial infections. Animals affected with either bacterial or viral pharyngitis should be treated with NSAIDs. Pharyngitis secondary to foreign bodies should be resolved with removal of the offending object and effective surgical drainage accompanied by excision of necrotic tissue.

Racehorses affected by pharyngeal lymphoid hyperplasia can be treated with topical and systemic anti-inflammatory agents such as flunixin meglumine, phenylbutazone, or dexamethasone. A commonly used topical anti-inflammatory treatment includes prednisolone, DMSO, glycerin, and nitrofurazone. Large pharyngeal masses can also be treated with contact diode laser photoablation. Some veterinarians have also found hyperimmunization helpful in managing pharyngeal lymphoid hyperplasia.

Calicivirus infections in cats may cause mild, moderate, or severe ulceration of the oropharyngeal mucosa. Although specific antiviral therapies are not available, affected cats should be treated with systemic antimicrobials to prevent secondary bacterial infection. Animals that cannot maintain their own hydration because of severe mucosal ulceration may require nutritional and electrolyte supplementation either intravenously or by extraoral alimentation.

Last full review/revision December 2013 by Jan F. Hawkins, DVM, DACVS

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