Characteristics of Chrysosporium spp. Pathogens Causing Skin Mycoses in Horses.

Equine skin mycoses are a significant concern in Kazakhstan's livestock industry due to the country's historical livestock farming practices, the development of equestrian sports, and food traditions. Skin infections are among the most common fungal infections in horses. Emerging pathogens of equine dermatophytosis include keratinophilic Chrysosporium spp., which can degrade and metabolize keratin found in superficial tissues. This, combined with their thermotolerance, contributes to their pathogenicity. In this study, we investigated the biological properties and pathogenicity of two Chrysosporium strains isolated from equine skin lesions in northern and central Kazakhstan. Our findings showed that the Chrysosporium isolates caused a variety of clinically expressed skin lesions and exhibited cultural and morphological similarities to Trichophyton mentagrophytes. Genetic identification using ribosomal gene sequencing revealed 98.9% identity with Chrysosporium kreiselii and Chrysosporium zonatum sequences in both cases. The C. kreiselii strain caused pronounced skin lesions typical of classic dermatomycoses, demonstrated both keratinophilic and keratinolytic properties, and showed resistance to antifungal drugs. In contrast, the C. zonatum strain, which caused atypical lesions such as dandruff and seborrhea, was more sensitive to antifungal agents and exhibited keratinophilic properties. Our results highlight the emergence of new pathogenic Chrysosporium strains responsible for skin pathology in horses in Kazakhstan. We recommend that the identification of Chrysosporium skin infections in horses in Kazakhstan be followed by a comprehensive retrospective analysis of newly identified pathogens, including a full characterization of their pathogenicity.