Sporothrix Species Causing Outbreaks in Animals and Humans Driven by Animal–Animal Transmission

The fungal genus Sporothrix (order Ophiostomatales) comprises a group of thermodimorphic pathogens that cause skin infections in humans and other mammals. Human sporotrichosis was first described in the Mid-Atlantic United States in 1898 by Schenck [1], followed shortly by reported animal infections [2]. Sporotrichosis occurs worldwide, with hyperendemic areas in Brazil, China, and South Africa [3,4]. Clinical sporotrichosis in mammals results from two major infection routes: animal transmission and plant origin. Both routes involve trauma to cutaneous and subcutaneous tissues to introduce Sporothrix propagules into the skin. Cutaneous lesions develop at the inoculation site, and local dissemination occurs through the lymphatics during the first two to three weeks of infection [5]. Infections transmitted via either animal or plant vector often escalate to outbreaks or epidemics. Over the last decade, molecular phylogeny has revolutionized the taxonomy of pathogenic Sporothrix species [6], altering our perceptions regarding epidemiology, host-association, virulence, and drug susceptibility [7–10]. The classical agent Sporothrix schenckii now comprises several molecular siblings nested in a clinical clade with S. brasiliensis, S. globosa, and S. luriei (Fig 1) [6]. S. brasiliensis is related to atypical and more severe clinical manifestations [11]. For decades, feline sporotrichosis in Brazil appeared only as sporadic, self-limiting clusters. However, the current outbreak of feline sporotrichosis because of S. brasiliensis in South and Southeast Brazil has risen to epidemic status, creating a public health emergency of international concern because of the potential of zoonotic transmission [9,12–15].