Cats are spreading a nasty fungal infection to people in Brazil.

A cat with Sporothrix brasiliensis infection (Courtesy of Dr. Marconi Rodrigues de Farias/Pontifical Catholic University of Parana)

The fungal species, Sporothrix brasiliensis, is spreading quickly among cats and has reached neighboring countries in South America, raising concerns within the Centers for Disease Control and Prevention. Veterinarians appear to be at higher risk for the disease than members of the general public.

Dr. Brendan Jackson, medical officer with the CDC's Mycotic Diseases Branch, said sporotrichosis had been an obscure disease in Brazil 20 years ago. It's now a serious problem in Rio de Janeiro and other Brazilian cities.

"They're seeing thousands of cases, tens of thousands of cases, and that's on a scale unlike we have seen for the classical Sporothrix," he said.

Sporothrix schenckii is found throughout the world, including the U.S. It causes "rose gardener's disease," a rare infection mostly linked to cuts and scrapes that are exposed to soil and plants. It can cause slow-healing lesions and, less often, respiratory infections or generalized infections with joint pain, headache, or seizures.

Dr. Jackson said S brasiliensis appears to cause more severe disease than other Sporothrix species, with skin infections that can spread to lymph nodes and, in immunocompromised people, cause lesions throughout the body.

The most severe disseminated infections can be fatal without antifungal treatment.

Dr. John Rossow is an Epidemic Intelligence Service officer with the Mycotic Diseases Branch and has worked with veterinarians and physicians who saw the disease in Brazil. He said cats pick up fungal spores with their paw pads and spread them to other cats through scratches and bites, resulting in lesions that are often located on the face.

In Brazil, the infections in cats are known as "clown nose" because of the swollen, infected scratches and nasal mucosa lesions.

"It can get pretty extensive and not just be isolated to the face," Dr. Rossow said.

The infection can be deadly for cats, and treatment tends to be lengthy and difficult, he said. Brazil has large populations of feral cats and owned cats that spend time outside.

Veterinarians are among the people most likely to be exposed, usually through bites and scratches, Dr. Rossow said. Dr. Jackson noted that veterinarians have developed eye infections after cats shook during examination of their facial lesions.

In a January 2017 article in PLOS Pathogens, "Zoonotic Epidemic of Sporotrichosis: Cat to Human Transmission," researchers wrote that S brasiliensis had higher virulence than other Sporothrix species during epizootics, and it tended to escalate to outbreaks or epidemics among cats.

From 1997-2011, Brazil's main referral center for mycosis treatment recorded about 4,200 cases of sporotrichosis involving humans, the article states. Treatment tends to require long-term antifungal administration, and researchers have found drug resistance with increasing frequency.

Dr. Jackson said S brasiliensis seems to have come from an environmental reservoir in far southern Brazil, and the various strains spreading among cats seem to be close relatives. But he said the CDC is trying to learn more about those origins.

Dr. Rossow said the CDC also is trying to learn more about the potential that people could bring the fungus to the U.S. Even a U.S. veterinary student participating in a spay-and-neuter program, for example, could bring home a healthy cat with paw pads colonized by fungal spores.

Dr. Rossow said veterinarians should be vigilant against this disease. Cats with the disease can have facial lesions and wounds that are slow to heal, and impression smears or other in-house diagnostic testing could reveal yeasts. He suggests that veterinarians tell diagnostic laboratories to keep S schenckii and S brasiliensis on the differential list.

Veterinarians who need testing help from the CDC can send a message to pathology cdc [dot] gov, Dr. Rossow said.

In December, Dr. Jackson also said during a CDC Zoonoses & One Health Updates presentation that Sporothrix is unusual for its ability to spread in both mold and yeast forms as well as its transmission from animals to people. He called for more study on disease spread and better testing methods in case of an outbreak.

If this fungus is neglected, it will grow, he said.