Sporothrix schenckii Complex (Sporotrichosis)

Microbiology

Phylogenetic, phenotypic, and physiologic differences have been identified among strains previously referred to as Sporothrix schenckii; therefore, isolates now are reported as members of the S. schenckii complex. ^, In addition to S. schenckii sensu stricto, other distinct species in the complex include S. mexicana, S. globosa, S. luriei, S. albicans, S. inflata, and S. brasiliensis. The species most commonly associated with clinical disease in humans and animals include S. brasiliensis, S. globosa, and S. schenckii. ^, The typical rosettes produced by these species are mostly indistinguishable; however, the sessile conidia display varying morphologies. S. luriei lacks sessile conidia and has a thick-walled budding yeast form. Calmodulin gene sequences are the most informative for species identification. Varied in vitro susceptibility may be responsible for varying clinical responses.

Epidemiology

Cutaneous infection, the most common manifestation in children and adults, usually follows traumatic implantation of Sporothrix. Minor trauma from thorns or wood splinters is a typical route of exposure. Lesions usually appear 1–4 weeks after inoculation. Pulmonary disease is less common but is acquired by inhalation. Animal-to-human transmission, usually from cats with lesions, can occur but is not common, although large outbreaks associated with cats have occurred; transmission from other animals, including armadillos, also has been reported.

Infection with S. schenckii complex occurs in all age groups, independent of race and sex, although some studies report a male predominance, possibly because of a higher number of exposures. Infections often are sporadic, occurring after outdoor exposures, although common-source outbreaks are described and can be traced to activities that result in contact with contaminated moss, hay, or wood. Ongoing zoonotic transmission from cats has been associated with epidemics of sporotrichosis in Brazil, Malaysia, and other regions. ^{, ,}

Investigation of outbreaks has led to insights into the epidemiology of sporotrichosis in the epidemic setting, but less information is available about the disease in areas where sporotrichosis is hyperendemic. Pappas and colleagues described 238 cases that occurred in a remote region of the central highlands of Peru. The incidence of disease ranged from 48 to 60 cases per 100,000 population and was highest among children 7–14 years of age, approaching 1 case per 1000. This report indicates that sporotrichosis in children is more common than is recognized, particularly in economically developing countries. Risk factors for sporotrichosis among children living in Peru included increased skin trauma (e.g., living in homes with dirt floors) and having contact with cats.