Epidemiology of infections due to zoophilic dermatophyte trichophyton simii, an update

Abstract

Trichophyton simii is an important zoophilic dermatophyte. It has two different names, one for the asexual form (the anamorph state) that occurs in the vertebrate host, and the other for the sexual form (teleomorph also called “perfect state”) produced by mating between anamorphs. The sexual state of T. simii belongs to the genus Arthroderma in the family Arthrodermataceae of the phylum Ascomycota of the Kingdom fungi. Zoophilic Trichophyton species include Trichophyton equinum, T. bullosum, members of the T. mentagrophytes complex, T. simii, and T. verrucosum. The clinical lesions caused by T. simii in humans and animals are usually inflammatory and erythematous. It can be distinguished from other Trichophyton species by its faster growth on agar media, forming finely granular colonies with white-to-pale yellow color on reverse and distinctive to fusiform 3–7 septate macroconidia converting into chlamydospores in older cultures, and pyriform microconidia, and inability to perforate hair in-vitro, and produce the enzyme urease . Trichophyton simii is known to infect monkeys, chickens, dogs, and humans worldwide, though infections are sporadic and epidemic potential and zoonotic risk for humans is low; this dermatophyte is also known to occur as a geophilic species in several countries. The literature search generated a lot of data on T. simii infections from several countries, namely India, Sri Lanka, Japan, Iraq, Iran, Saudi Arabia, Belgium, France, the USA, and Brazil; many of the reports lacked details of clinical lesions and did not mention about treatment/outcome of infections. The results are analyzed and presented concisely in the tables. There is need for investigating the epidemiology of T. simii infections in countries from where, human T. simii infections have been reported, and occurrence of this dermatophyte in soil by employing conventional mycological methods and a newly developed PCR technique based on ITS genomic sequences of this dermatophyte.