Potential Role of Microbiota in Perianal Fistulas

ArticleLast Updated July 20242 min read
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Cain CL, White E, Citron LE, et al. Longitudinal evaluation of the cutaneous and rectal microbiota of German shepherd dogs with perianal fistulas undergoing therapy with ciclosporin and ketoconazole. Vet Dermatol. 2024. doi:10.1111/vde.13249

Research Note

Canine perianal fistulas are immune-mediated, and a proposed etiology is immune dysregulation in response to microbes in the anal or perianal region. Oral cyclosporine with or without ketoconazole is the mainstay of treatment; however, long-term administration is often needed, and relapses after treatment cessation are common.

This study evaluated cutaneous and rectal microbiota in German shepherd dogs with (n = 11) and without (n = 15) perianal fistulas. Swabs of the rectum, axilla, and fistula sites were collected from affected dogs at enrollment, day 30, and day 60 during treatment with modified cyclosporine and ketoconazole; swabs of the rectum, axilla, and perianal region were similarly obtained from healthy, untreated dogs. Ribosomal RNA gene sequencing revealed that alpha diversity between affected and healthy dogs was not significantly different at any site. Beta diversity of rectal or fistula site samples, however, differed significantly. In affected dogs, relative abundance of Prevotella spp increased and Staphylococcus spp decreased over time with lesion resolution. Further study of whether manipulation of microbe populations can play a role in perianal fistula treatment is warranted.