Objectives:
Trichophyton benhamiae, T. erinacei and related species are increasingly reported as a cause of dermatophytosis in pet or companion animals and their breeders or owners worldwide. A considerable genetic and phenotypic variability has been revealed in these emerging pathogens. To substantiate the initial finding, we assembled strains isolated from various hosts in different European countries, Japan and the USA. We conducted DNA sequencing of several genetic loci, microsatellite analysis, analysis of morphology, and physiological testing to elucidate whether the detected level of variability reflects undescribed species diversity or a high infraspecific variability.

Methods:
A total number of 326 and 146 strains from T. benhamiae and T. erinacei complexes, respectively, associated with human and animal dermatophytoses were analysed using two sequenced loci, 10 and 7 microsatellites loci, respectively, and morphological and physiological methods.

Results:
Among T. benhamiae isolates, four distinct species were revealed, including three undescribed species (S1-S3). Species S1 and S2 have guinea pig as an exclusive host and are abundantly reported from Europe. These species differ strikingly by phenotype, physiology, produced secondary metabolites and reproductive strategy (sexual versus clonal). Species S1 is responsible for the current epidemic of dermatophytosis in Europe. Trichophyton benhamiae s. str. occurs mostly in America and is associated with infections in dogs, while species S3 has been isolates in Europe and Japan from rabbits and their owners. Only two poorly defined populations were found among T. erinacei isolates. These populations were strongly host-specific. First population was specific for African pet hedgehogs (Atelerix albiventris) and most frequently associated with mycoses in human (89% of human isolates examined). The second population was isolated exclusively from European hedgehogs. Remaining species related to mentioned pathogens, i.e., T. eriotrephon and T. bullosum, also occur in Europe but are much less frequent.

Conclusion:
In this study, we elucidated genetic diversity, population structure and main hosts of zoophilic pathogens from T. benhamiae and T. erinacei complexes. Based on genetic relatedness of strains of both populations, we suggest that the most virulent and closely related genotypes of T. benhamiae complex (species S1) was introduced to Europe from North America. High genetic divergence and phenotypic differences between “populations” of T. benhamiae indicate that they can be considered independent species. In contrast, molecular methods detected relatively low infraspecific variability in T. erinacei isolates that clustered into two populations occurring on different hosts.

4 / New and emerging zoophilic dermatophytes in Europe