The thermally dimorphic fungus Sporothrix schenckii is the etiological agent of human and
animal sporotrichosis and belongs to the recently proposed Sporothrix complex, which includes other
species based on the phylogenetic-species concept. Sporotrichosis is a deep mycosis and clinical
manifestations vary from a benign lymphocutaneous form to less frequent disseminated and
extracutaneous forms, mainly associated with an immunocompromised host. Animals are also
susceptible to S. schenckii infection and cats (Felis catus) are known for greater predisposition to this
fungal infection. Only recently has zoonotic transmission of this disease been reported in greater detail
in the literature and these new data are changing the epidemiological concept of this mycosis. The gold
standard for the diagnosis of sporotrichosis remains fungus isolation from biological specimens, but
new diagnostic tools are under development for both human and animal sporotrichosis. The outcome of
an infectious disease is not only associated with virulence factors inherent to the pathogen, but also the
host immune response. Thermotolerance is described as a virulence factor for S. schenckii and is
associated with the capacity of a clinical or environmental isolate to cause host damage. However, the
description of new species and genotypes among clinical isolates and the observation that
thermotolerant isolates can exhibit differences in virulence using in vivo models strongly supports the
concept that other virulence factors could be related to the clinical manifestations or modulate the host
immune response. This chapter will address new data in relation to the clinical, epidemiological and
biological aspects of S. schenckii.
Keywords: Sporothrix schenckii, sporotrichosis, epidemiology, virulence factors, host-fungus interplay,
clinical diagnosis, saprophytic, thermotolerance, mycosis, taxonomy, phenotypic analysis.
