Granulomatous colitis associated with infection in a young cat

Case summary A 1-year-old spayed female mixed-breed cat presented with chronic large bowel diarrhoea. The cat was treated with various antibiotics, prednisolone and dietary supplements without significant improvement. Endoscopic examination revealed an irregular colonic mucosa with multifocal erosio...

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Main Authors: Kento Ishikawa, James K Chambers, Ko Nakashima, Takehiro Sakai, Kazuyuki Uchida
Format: Article
Language:English
Published: SAGE Publishing 2025-07-01
Series:Journal of Feline Medicine and Surgery Open Reports
Online Access:https://doi.org/10.1177/20551169251348548
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author Kento Ishikawa
James K Chambers
Ko Nakashima
Takehiro Sakai
Kazuyuki Uchida
author_facet Kento Ishikawa
James K Chambers
Ko Nakashima
Takehiro Sakai
Kazuyuki Uchida
author_sort Kento Ishikawa
collection DOAJ
description Case summary A 1-year-old spayed female mixed-breed cat presented with chronic large bowel diarrhoea. The cat was treated with various antibiotics, prednisolone and dietary supplements without significant improvement. Endoscopic examination revealed an irregular colonic mucosa with multifocal erosion and haemorrhage. Impression smears of the colonic mucosa contained large numbers of unicellular round-to-oval organisms and macrophages. Histologically, granulomatous inflammation with numerous organisms was observed in the lamina propria of the colonic mucosa. The organisms had a cell wall and internal segmentation, which were positive on periodic acid–Schiff and Grocott’s methenamine silver staining. Immunohistochemically, CD204-positive macrophages had accumulated in the lesions. Ultrastructural examination revealed dense bodies and starch granules, and the absence of chloroplasts in the cytoplasm of the organisms. PCR and a sequence analysis detected the Prototheca bovis 18S rRNA gene in formalin-fixed, paraffin-embedded colonic mucosa tissue. Based on these findings, the cat was diagnosed with granulomatous colitis associated with P bovis infection. Relevance and novel information This first report of feline intestinal protothecosis suggests that Prototheca species infection should be considered in the differential diagnosis of cats with treatment-resistant chronic large bowel diarrhoea.
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spelling doaj-art-b0f98fb0948049ada2d66ab40ba6fe3b2025-08-20T03:51:19ZengSAGE PublishingJournal of Feline Medicine and Surgery Open Reports2055-11692025-07-011110.1177/20551169251348548Granulomatous colitis associated with infection in a young catKento Ishikawa0James K Chambers1Ko Nakashima2Takehiro Sakai3Kazuyuki Uchida4University of Tokyo, Tokyo, JapanUniversity of Tokyo, Tokyo, JapanJapan Small Animal Medical Center, Saitama, JapanJapan Small Animal Medical Center, Saitama, JapanUniversity of Tokyo, Tokyo, JapanCase summary A 1-year-old spayed female mixed-breed cat presented with chronic large bowel diarrhoea. The cat was treated with various antibiotics, prednisolone and dietary supplements without significant improvement. Endoscopic examination revealed an irregular colonic mucosa with multifocal erosion and haemorrhage. Impression smears of the colonic mucosa contained large numbers of unicellular round-to-oval organisms and macrophages. Histologically, granulomatous inflammation with numerous organisms was observed in the lamina propria of the colonic mucosa. The organisms had a cell wall and internal segmentation, which were positive on periodic acid–Schiff and Grocott’s methenamine silver staining. Immunohistochemically, CD204-positive macrophages had accumulated in the lesions. Ultrastructural examination revealed dense bodies and starch granules, and the absence of chloroplasts in the cytoplasm of the organisms. PCR and a sequence analysis detected the Prototheca bovis 18S rRNA gene in formalin-fixed, paraffin-embedded colonic mucosa tissue. Based on these findings, the cat was diagnosed with granulomatous colitis associated with P bovis infection. Relevance and novel information This first report of feline intestinal protothecosis suggests that Prototheca species infection should be considered in the differential diagnosis of cats with treatment-resistant chronic large bowel diarrhoea.https://doi.org/10.1177/20551169251348548
spellingShingle Kento Ishikawa
James K Chambers
Ko Nakashima
Takehiro Sakai
Kazuyuki Uchida
Granulomatous colitis associated with infection in a young cat
Journal of Feline Medicine and Surgery Open Reports
title Granulomatous colitis associated with infection in a young cat
title_full Granulomatous colitis associated with infection in a young cat
title_fullStr Granulomatous colitis associated with infection in a young cat
title_full_unstemmed Granulomatous colitis associated with infection in a young cat
title_short Granulomatous colitis associated with infection in a young cat
title_sort granulomatous colitis associated with infection in a young cat
url https://doi.org/10.1177/20551169251348548
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