A Rare Case of Cutaneous Infection by Corynascus verrucosus in a Shih Tzu Dog: Molecular Identification and Phylogenetic Analysis.

BACKGROUND: Fungal infections are important causes of dermatological disease in companion animals and may involve a diverse range of clinically relevant fungal pathogens. Accurate identification of the causative agent is essential for appropriate diagnosis, treatment and assessment of potential zoonotic risks. OBJECTIVES: This study aimed to characterize a fungal isolate from a canine cutaneous lesion in Tehran, Iran, using morphological, molecular and phylogenetic analyses. METHODS: Skin scrapings were aseptically collected from a dog presenting with pruritus and scaling, using sterile techniques microscopic examination and fungal culture. Microbiological observations were inconclusive for species-level identification. Hence, target isolate was subjected to PCR amplification of the internal transcribed spacer (ITS) region using ITS1 and ITS4 universal primers. RESULTS: The ITS1-5.8S rDNA-ITS2 region was successfully amplified and sequenced using the universal ITS1 and ITS4 primers, and the sequence was deposited in the NCBI GenBank (PV082530). BLAST analysis showed 99.36% nucleotide similarity to a reference sequence of Corynascus verrucosus. In the maximum likelihood analysis placed the Iranian isolate within the broader Corynascus lineage, clustering closely with C. verrucosus reference sequences from different geographic regions. Morphological findings, particularly large, round, verrucose conidia, supported the molecular identification. Overall, the combined morphological, molecular and phylogenetic findings supported identification as C. verrucosus. CONCLUSIONS: This case highlights the occurrence of an uncommon C. verrucosus isolate in a canine cutaneous lesion and demonstrates the value of integrating morphological, molecular, and phylogenetic approaches for fungal identification. The findings also emphasize the importance of cautious interpretation of molecular data when closely related fungal taxa show high sequence similarity.