Zoonotic Alert: Highly Transmissible Cat-Borne Fungus Sporothrix brasiliensis Confirmed in Uruguay

MALDONADO, URUGUAY — Public health authorities and researchers have confirmed a significant shift in the regional infectious disease landscape following the detection of Sporothrix brasiliensis, a highly virulent fungus, in the southeastern coastal departments of Maldonado and Rocha. Previously concentrated in Brazil, the pathogen is now spreading through feline populations in Uruguay, marking a critical transition from environmental to animal-to-human transmission that experts warn could signal a broader South American health threat.

The discovery, documented by a research team at the Universidad de la República as recently as March 2026, marks a departure from Uruguay’s historical experience with sporotrichosis. For decades, cases in the region were typically linked to “rose gardener’s disease”—contracted from soil or thorny plants—or specific interactions with armadillos. The arrival of S. brasiliensis introduces a “super-spreader” dynamic, where stray and domestic cats act as the primary vectors for a more aggressive form of the disease.

A Changing Epidemiological Pattern

For nearly 40 years, sporotrichosis in Uruguay followed a predictable, low-level pattern. A retrospective review led by Dr. Elisa Cabeza identified 157 cases between 1984 and 2022, with the vast majority (128 cases) resulting from armadillo hunting. However, the new findings indicate that S. brasiliensis has established local transmission cycles independent of traditional sources.

“This detection recasts a single case as evidence of a harder-to-control fungal threat gaining a foothold in South America,” says Dr. Cabeza. Her team identified the fungus in multiple cats and humans who had no direct contact with the initial “index” case, suggesting the pathogen is already circulating within neighborhood cat populations.

The biological secret to the fungus’s success lies in its dimorphic nature. In the cool environment of the soil or a cat’s claws, it exists as a mold (mycelia). Once it enters the warm environment of a human or animal body—typically around 37°C—it transforms into a yeast phase. This switch allows the fungus to invade deeper tissues and evade the host’s immune response more effectively than its less-virulent cousins.

Symptoms: Identifying the “Feline Signature”

In humans, the infection—now being termed zoonotic sporotrichosis—usually begins as a small, firm, painless red bump at the site of a scratch or bite. Over weeks, this can evolve into an open sore or ulcer. A hallmark of the disease is the “lymphocutaneous” spread, where new nodules form a line climbing up the arm or leg, following the path of lymphatic vessels.

In cats, the symptoms are often more severe and visible:

• Deep Ulcers: Open, non-healing sores, particularly on the nose, face, and paws.

• Respiratory Distress: Frequent sneezing, which can aerosolize the fungus.

• Behavioral Changes: Increased irritability due to discomfort, leading to more frequent scratches or bites.

“The fungal load in infected cats is incredibly high,” notes Dr. Anastasia Litvintseva, a mycologist with the Centers for Disease Control and Prevention (CDC). “Unlike other species of Sporothrix, where the fungus is sparse in the wound, S. brasiliensis is so concentrated in feline lesions that even a minor scratch carries a high risk of infection.”

Diagnostic Hurdles and Treatment Realities

One of the primary challenges facing Uruguayan health officials is misdiagnosis. Early fungal lesions can look remarkably like common bacterial abscesses or “cat scratch disease” (Bartonella).

“The infection is curable,” Dr. Cabeza emphasizes, but she notes that delays in diagnosis often lead to more extensive tissue damage. Diagnosis is confirmed through a microscopic examination of scrapings—which often reveal “asteroid bodies,” a specific immune-fungal structure—or by growing a culture on Sabouraud agar, a specialized laboratory medium.

Standard Treatment Protocols

While cure rates in humans exceed 85%, S. brasiliensis is proving stubborn. Research indicates that low-dose treatments (100 mg) fail in roughly 42% of cases, necessitating higher doses and longer courses of therapy—averaging about 187 days—to fully clear the pathogen.

The “One Health” Perspective: Public Health Implications

The World Health Organization (WHO) has recognized sporotrichosis as a neglected tropical disease (NTD), emphasizing the need for integrated “One Health” strategies that address human, animal, and environmental health simultaneously.

The expansion of the fungus is not merely a veterinary issue; it is a socio-economic one. The movement of stray cats across porous borders has fueled the spread from Brazil (where over 11,000 human cases have been recorded in the last decade) into Argentina, Paraguay, and now Uruguay.

For the general public, experts recommend several preventative measures:

1. Monitor Pets: Check outdoor cats regularly for non-healing wounds or “weeping” sores.

2. Safe Handling: Use gloves when gardening or handling stray animals, and wash any scratches immediately with soap and water.

3. Veterinary Care: If a pet is diagnosed, it must be isolated from other animals and family members, particularly children under two and the immunocompromised, who are at higher risk for disseminated disease.

Limitations of Current Data

While the rise of S. brasiliensis is concerning, researchers urge a balanced perspective. The scale of the outbreak in Uruguay remains small compared to the hyperendemic regions of Brazil. Furthermore, true antifungal resistance remains rare (occurring in less than 5% of cases); most treatment failures are attributed to high initial fungal loads or premature cessation of medication.

Public health advocates also caution against “cat culls” or the abandonment of pets, which can worsen the problem by increasing the number of roaming, untreated animals. Instead, they advocate for subsidized veterinary care and widespread spay/neuter programs to stabilize the feline population.

Looking Ahead

As climate patterns shift and urban areas expand into natural habitats, the “jump” of pathogens from wildlife to domestic animals and then to humans is becoming more frequent. The Uruguayan outbreak serves as a sentinel event, prompting calls for increased surveillance across the Americas. For now, vigilance, early diagnosis, and responsible pet ownership remain the most effective tools in containing this emerging fungal threat.

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.

References

• Earth.com. “Fungus that spreads from cats to humans has been detected, raising concerns among scientists.” March 26, 2026.