Sporotrichosis caused by Sporothrix brasiliensis is an emerging zoonosis in South America, with Brazil representing the epicenter of a major ongoing epizootic. In Argentina, human and feline cases have increased over the past decade, predominantly in the Buenos Aires metropolitan area. However, autochthonous zoonotic transmission within Buenos Aires City has not been previously documented.

To describe the first documented feline and zoonotic outbreak caused by S. brasiliensis in Buenos Aires City, involving cat-to-cat and cat-to-human transmission.

Two cats with ulcerative cutaneous lesions were evaluated at the Instituto de Zoonosis Luis Pasteur (Buenos Aires City) in 2025. Clinical samples were cultured, and isolates were identified by partial sequencing of the β-tubulin gene. Antifungal susceptibility testing was performed to determine the minimum inhibitory concentration (MIC) of itraconazole. Clinical evolution and treatment outcomes of both cats, as well as zoonotic transmission to the owner, were documented.

Both isolates were identified as S. brasiliensis and showed an itraconazole MIC of 0.03 mg/L. Both cats were successfully treated with oral itraconazole, achieving clinical cure after approximately five months of therapy. Zoonotic transmission to the owner occurred in both cases, confirming the public health implications of feline sporotrichosis.

These cases document the first recognized feline and zoonotic outbreak caused by S. brasiliensis in Buenos Aires City and provide evidence of cat-to-cat and cat-to-human transmission. The findings reinforce the emergence of S. brasiliensis in urban Argentina and highlight the need for a One Health approach integrating veterinary and human medicine to improve surveillance, early diagnosis, and disease control.