A fungal infection, previously contained largely to Brazil, is gaining a foothold in South America, and a new study highlights a surprising vector: cats. Researchers in Uruguay have documented the spread of Sporothrix brasiliensis, a fungus that causes skin infections, confirming cases in people, pets, and other animals across the departments of Maldonado and Rocha on the country’s southeastern coast. This isn’t an isolated incident, but rather evidence of a potentially harder-to-control outbreak, shifting how health officials understand the transmission of this disease.
The initial alarm stemmed from a single case, but investigations led by Dr. Elisa Cabeza at the Universidad de la Republica (Udelar) revealed a more widespread problem. Cabeza’s team discovered sick cats in both departments, with no direct connection to the first identified case, suggesting local transmission was already underway. This finding fundamentally changed the understanding of the outbreak, moving it beyond a single household issue to a broader public health concern centered on feline spread.
Sporothrix brasiliensis thrives on open sores found on infected cats, particularly around the nose, face, mouth, and paws. These wounds harbor large amounts of the fungus, which can easily transfer to humans through scratches, bites, or even contact with wound fluid. A recent review published in Medical Mycology (PMID: 37233242) detailed how cats can transmit a significant number of fungal cells through these routes. The role of stray cats is particularly concerning, as they often fight, roam freely, and remain undiagnosed, facilitating the fungus’s spread between neighborhoods.
Why Cats Are Effective Spreaders
The fungus exhibits a unique ability to adapt to its environment, a characteristic known as dimorphism. Outside a living host, Sporothrix brasiliensis grows as branching threads. Still, when it enters a warm-blooded animal, body heat triggers a transformation into a compact yeast form. This smaller form is better equipped to settle into damaged skin and multiply within living tissue. This temperature-driven switch allows the fungus to survive both indoors and outdoors, increasing its potential for infection.
Recognizing the Symptoms
In humans, sporotrichosis typically begins as a small, red bump that breaks open, often following a scratch or minor injury. Over time, additional bumps may appear in a line, tracing the path of the fungus through the lymphatic channels beneath the skin. In cats, symptoms often manifest as persistent wounds, crusts, and hair loss, particularly on the face and head. Red, draining eyes can also be a sign of infection. While the illness rarely spreads beyond the skin and underlying tissues, early detection is crucial.
Diagnosis and Treatment
Diagnosing sporotrichosis involves examining samples from sores under a microscope or cultivating the fungus in a laboratory setting. What we have is important because the initial symptoms can easily be mistaken for bacterial infections, leading to ineffective antibiotic treatment. “The infection is curable,” Dr. Cabeza stated, noting that common antifungal medications are effective, though treatment can last for weeks or months. Managing the infection in cats, however, presents a greater challenge.
Who is Most Vulnerable?
Individuals with weakened immune systems, young children, and older adults are at the highest risk of developing severe complications from Sporothrix brasiliensis. While rare, the infection can spread to joints, lungs, or even the brain’s lining, making prompt diagnosis and treatment essential. Udelar investigators specifically highlighted the increased vulnerability of children under two and older adults.
The Expanding Outbreak
The spread isn’t limited to Uruguay. A 2024 report (PMID: 38420181) documented two human cases in Argentina linked to contact with sick cats. The World Health Organization (WHO) has acknowledged the growing outbreak, stating that affected areas in South America have reported over 11,000 human cases in the past decade. The movement of cats, both legal and informal, across borders is now recognized as a significant factor in the fungus’s dissemination.
Before this recent surge, Uruguay primarily saw sporotrichosis cases linked to contact with soil, plants, or armadillos. A Udelar review (PMID: 35330324) found 157 diagnosed cases over 38 years, with 128 attributed to armadillo scratches during hunting. This historical pattern underscores the shift in transmission dynamics and the heightened concern surrounding the cat-borne route.
Controlling the spread is complicated by the prevalence of stray cats, many of whom remain undiagnosed and untreated. A study published in Medical Mycology (PMID: 36318452) even detected the fungus in droplets expelled when infected cats sneezed, expanding the potential routes of transmission beyond direct contact. Effective control requires a coordinated effort involving animal care, medical professionals, and community reporting.
The detection of Sporothrix brasiliensis in Uruguay signifies that the fungus, once largely confined to Brazilian cat outbreaks, has established a firmer presence across southern South America. The study, published in Medical Mycology Case Reports (DOI: S2211753924000071), underscores the importance of rapid diagnosis, treatment for both pets and people, and improved control of stray cat populations to prevent further spread.
Health officials are continuing to monitor the situation closely, and further updates will be provided as new information becomes available. The next key step will be a comprehensive assessment of the prevalence of the fungus in cat populations across the region, scheduled for release by the Uruguayan Ministry of Public Health in early July.
Have you or someone you understand been affected by this fungal infection? Share your experiences and thoughts in the comments below. And please, share this article to help raise awareness about this emerging public health concern.
