Severe cryptococcal granulomas of the nasopharynx in a horse treated with standing endoscopic laser surgery and oral fluconazole
Authors: Daniel A. J., Thachil A., Savory‐Davis M.
Journal: Equine Veterinary Education
Summary
An Arabian mare presented with a four-month history of bilateral mucopurulent nasal discharge that failed to respond to repeated antimicrobial courses and intravenous sodium iodide therapy, with radiography and endoscopy revealing multiple ulcerated granulomatous masses in the nasopharynx. Cryptococcus terrestris was identified only after histopathological examination and culture of tissue obtained via standing endoscopic laser surgery—surface cultures had yielded only mixed bacterial populations—highlighting the diagnostic challenge these infections present in horses. The combination of surgical de-bulking using standing laser endoscopy followed by systemic fluconazole therapy (initial 14 mg/kg orally, then 5 mg/kg twice daily for 11 weeks total, guided by repeat endoscopic assessment) resulted in complete resolution and sustained remission exceeding 18 months, with the horse returning to competition. This case represents the first documented equine infection with C. terrestris and demonstrates that deep tissue sampling is essential when superficial cultures remain non-diagnostic in the face of persistent nasopharyngeal disease; practitioners should maintain a high index of suspicion for fungal aetiologies when standard antimicrobial protocols fail. The successful outcome supports standing endoscopic laser surgery as a viable approach for mechanical reduction of granulomatous burden combined with prolonged azole therapy, though the rarity of this condition means further cases are needed to establish optimal treatment protocols.
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Practical Takeaways
- •Cryptococcal nasopharyngeal infection should be considered in horses with chronic, antimicrobial-resistant bilateral nasal discharge; standard bacterial cultures may be negative despite active infection
- •Standing endoscopic laser surgery is a viable approach for surgical de-bulking of accessible nasopharyngeal masses, with tissue biopsy essential for definitive diagnosis
- •Oral fluconazole at 5 mg/kg twice daily combined with surgical intervention can achieve long-term resolution; endoscopic follow-up guides appropriate treatment duration
Key Findings
- •First reported case of Cryptococcus terrestris infection in a horse, presenting as bilateral nasopharyngeal granulomas unresponsive to antimicrobials and sodium iodide
- •Standing endoscopic laser surgery combined with oral fluconazole (5 mg/kg q12h for 11 weeks) achieved complete resolution and >1.5 years infection-free survival
- •Diagnosis required histopathology and culture from surgically excised tissue rather than surface exudate cultures, highlighting diagnostic challenges with cryptococcal infections