A Super Fungus Is Evolving in Polluted Cities – And It’s Spreading Through Cats

A deadly fungal epidemic in Brazil is evolving fast: pollution, cats, and genetics may be fueling its unstoppable spread.

Brazil is facing the world’s largest and most persistent sporotrichosis epidemic, a fungal infection spread primarily through cats. A new study reveals an alarming genetic diversity in the fungus, suggesting that urban pollutants may be accelerating its evolution. Researchers identified molecular markers that could enhance diagnostics and treatments, while also highlighting the rapid adaptation and virulence of Sporothrix brasiliensis.

Unraveling the Largest Sporotrichosis Epidemic

A recent study led by Dr. Anderson Messias Rodrigues of the Federal University of São Paulo, and funded by the São Paulo Research Foundation (FAPESP), has revealed new insights into Brazil’s ongoing sporotrichosis epidemic, the largest and longest-lasting outbreak of this fungal infection in the world.

Sporotrichosis is a chronic disease that primarily affects the skin and lymphatic system, and in some cases, internal organs. It is usually caused by fungi from the Sporothrix genus. Unlike most fungal infections, sporotrichosis can be transmitted from animals to humans, with infected cats serving as a major source of infection through scratches, bites, or contact with bodily fluids.

Genetic Diversity and Urban Pollutants

The research team analyzed 104 isolates of Sporothrix fungi, focusing on the 3-carboxymuconate cyclase (CMC) gene, which produces an important antigen known as Gp60-70. They discovered 79 distinct genetic variants, revealing a much higher level of genetic diversity than previously thought. Molecular analysis showed high levels of polymorphism in Sporothrix brasiliensis and Sporothrix schenckii, suggesting recent population growth or adaptive evolution.

The researchers propose that exposure to common urban pollutants, such as benzene, toluene, and polycyclic aromatic hydrocarbons, may be driving this evolution. These chemicals could act as environmental stressors, favoring fungal strains with increased CMC activity. Since the CMC enzyme helps break down aromatic compounds through the β-ketoadipate pathway, this adaptation may give these strains a survival advantage in polluted environments.

New Molecular Targets for Diagnosis and Treatment

The study also predicted key B-cell epitopes and conserved glycosylation sites—potential targets for diagnostics, vaccines, and antifungal therapies. The presence of high-frequency derived alleles in S. brasiliensis suggests rapid adaptation, potentially leading to increased virulence. Furthermore, the CMC gene has proven to be a more effective molecular marker than traditional markers, offering improved resolution for differentiating strains and enhancing epidemiological surveillance.

The Spread and Impact of Sporothrix brasiliensis

Sporothrix brasiliensis, the most virulent Sporothrix species, is a key driver of the Brazilian epidemic. Compared with other species, it presents greater pathogenicity, transmission efficiency, and antifungal resistance. The outbreak, which originated in Rio de Janeiro in the late 1990s, has spread nationwide and to neighboring countries, fueled by high cat populations, socioeconomic challenges, and gaps in disease surveillance. Cat-to-cat and cat-to-human transmission are significant contributors to the rapid spread of S. brasiliensis.

Advancing Disease Control and Surveillance

“These findings offer a new molecular perspective on Sporothrix evolution and virulence,” says Dr. Rodrigues. “Understanding these fungal adaptations is crucial for developing better tools to diagnose, monitor, and control the spread of sporotrichosis among humans and cats.”

This study underscores the urgent need for enhanced fungal surveillance, particularly in areas experiencing an increase in cat-transmitted sporotrichosis. Identifying genetic markers linked to virulence could lead to new control strategies in both human and veterinary medicine, helping to address this growing public health crisis.

Reference: “Genetic diversity and molecular evolution of 3-carboxymuconate cyclase (Gp60–70), the major antigen in pathogenic Sporothrix species” by Jamile Ambrósio de Carvalho, Thiago Costa Machado, Alexandre Augusto Sasaki, Fabian Glaser, Primavera Alvarado, Alexandro Bonifaz, Sarah Santos Gonçalves, Isabella Dib Gremião, Sandro Antonio Pereira, Olga Fischman Gompertz, Zoilo Pires de Camargo and Anderson Messias Rodrigues, 8 March 2025, Mycology.
DOI: 10.1080/21501203.2025.2467118

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