Zoonotic sporotrichosis. Transmission to humans by infected domestic cat scratching: report of four cases in Sao Paulo, Brazil

Background Sporotrichosis is a chronic, granulomatous, deep mycosis caused by the dimorphic fungus Sporothrix schenckii that usually results in indole nt cutaneous lesions. Objective To describe four cases of human sporotrichosis transmitted by dom estic cats in south-eastern Brazil. Methods Confirmation of the diagnosis was performed by histopathology, cult ure, and/or inoculation of hamsters. Results In all cases, the clinical findings in both cat and human groups we re highly distinctive of the disease. In all human cases, there was a previ ous history of cat scratching before the development of lymphocutaneous les ions. Histopathology of the human lesions demonstrated the classical granul omatous and exudative pattern with scarce or absent fungal elements, Conver sely, in cats, the cutaneous lesions were multiple, extensive, necrotic, ex udative, and ulcerated. Histopathology revealed a widespread histiocytic re action with a large number of fungal organisms. Disseminated lymphatic and visceral mycotic infection was observed in two necropsied cats. Conclusions Domestic cats may be an important carrier of agents of sporotri chosis to humans.