Canine intestinal histoplasmosis containing hyphal forms

• Published in: Journal of veterinary diagnostic investigation Vol. 25; no. 2; pp. 304 - 307
• Main Authors: Schumacher, Loni L, Love, Brenda C, Ferrell, Mark, DeSilva, Udaya, Fernando, Ruchika, Ritchey, Jerry W
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01-03-2013
• Subjects: Ajellomyces; Animals; colitis; colon; diarrhea; Dog Diseases - microbiology; Dogs; duodenum; enteritis; Histoplasma - genetics; Histoplasma - isolation & purification; Histoplasma - physiology; Histoplasma capsulatum; histoplasmosis; Histoplasmosis - microbiology; Histoplasmosis - veterinary; hyphae; Hyphae - physiology; Intestinal Diseases - microbiology; Intestinal Diseases - veterinary; Intestines - microbiology; Intestines - pathology; jejunum; laparotomy; Male; Phylogeny; polymerase chain reaction; silver; veterinarians; yeasts; Oklahoma; holomorph; Histoplasma capsulatum; Ajellomyces capsulatus; histoplasmosis
• ISSN: 1040-6387; 1943-4936
• DOI: 10.1177/1040638713479604

A 12-year-old intact male Miniature Schnauzer dog with chronic diarrhea that was unresponsive to empirical treatment was presented to a referring veterinarian. A laparotomy was performed, and formalin-fixed biopsies of duodenum, jejunum, and colon were sent to Oklahoma Animal Disease Diagnostic Laboratory for evaluation. Histologic examination revealed a severe, diffuse, granulomatous enteritis and colitis with intralesional yeast and hyphal forms. Grocott methenamine silver stains revealed short, aseptate hyphae co-mingled with 2–8 µm, oval to round yeast organisms consistent with Histoplasma capsulatum. The atypical presentation of both yeast and hyphal forms prompted identification of the organism. Direct sequencing of a polymerase chain reaction product from paraffin-embedded intestinal samples confirmed the presence of Ajellomyces capsulatus with a homology over 99% to several sequences in GenBank. Ajellomyces capsulatus is the holomorphic name for H. capsulatum. Therefore, the mycelial form of a dimorphic fungus such as H. capsulatum can coexist with yeast cells within lesions of histoplasmosis. Following diagnosis, the dog was treated with itraconazole for 6 months and has improved.