Canine dermatophytic kerion caused by Microsporum canis: two case reports.

Dermatophytosis is a superficial, highly contagious mycosis caused mainly by keratinophilic fungi of the genera Microsporum, Trichophyton and Nannizzia. This report describes two clinical cases of dermatophytic kerion in dogs caused by Microsporum canis. In both, direct microscopic examination of hairs revealed ectothrix arthroconidia, and fungal culture yielded colonies morphologically consistent with M. canis. Species identification was confirmed by PCR amplification and partial sequencing of the ribosomal ITS region, followed by BLAST analysis and phylogenetic reconstruction. Antifungal susceptibility testing was performed by agar diffusion. Systemic antifungal therapy using pulse regimens of itraconazole or terbinafine, combined with topical treatment and environmental decontamination, resulted in complete clinical and mycological cure in both patients. These cases emphasize the importance of considering dermatophytosis, particularly kerion, in the differential diagnosis of deep inflammatory skin lesions in dogs. Early recognition and appropriate antifungal therapy are essential to achieve successful outcomes and to reduce the risk of zoonotic transmission.