Population biology of Trichophyton erinacei, an emerging cause of dermatophytosis
Trichophyton erinacei is increasingly reported as a cause of dermatophytosis in wild and pet hedgehogs, their breeders, and owners worldwide. The pathogen was originally described in the European hedgehog (Erinaceus europaeus), occurring naturally in the UK and Northern and Western Europe; but it has also been imported to New Zealand and Japan. Moreover, T. erinacei has been reported from the African wild-living four-toed hedgehog (Atelerix albiventris), which has become a popular pet animal worldwide. Little is known about the taxonomy and population genetics of this pathogen despite its increasing importance in clinical practice. Especially it is not known if there are different populations or even cryptic species associated with different animal hosts or geographic regions. To answer these questions, we assembled more than 170 strains from animals and humans isolated in different European countries, Africa, New Zealand, and Japan. We conducted DNA sequencing of four genetic loci, microsatellite analysis (7 loci), analysis of morphology, and physiological testing. Three populations were found among the examined isolates. One population was associated with free-living African hedgehogs, a second with pet African hedgehogs from the households of different countries, and the last population was isolated exclusively from wild-living European hedgehogs (Erinaceus europaeus). Based on the close genetic relatedness of strains from the first two populations, we assume that the population of T. erinacei occurring in pet African hedgehogs originated from Africa and was introduced into many countries by animal trade. The low genetic diversity of the pathogen in pet hedgehogs may indicate a founder effect and clonal spread of the pathogen. Preliminary phenotypic data and relatively low genetic divergences between populations do not support recognition of these population as separate species despite significant ecological differences.