A cluster of rare fungal infections was found in two pet cats and a vet who treated them, the Center for Disease Control and Prevention said Wednesday in a report in the journal Emerging Infectious Diseases.
The three cases — which took place in late 2022 and early 2023 — were caused by a fungus called Sporothrix schenckii.
The report comes as the CDC is monitoring the spread of a similar fungal infection, also in cats, in South America. That infection is spread by a related fungus called Sporothrix brasiliensis and hasn’t been detected in the United States.
Sporotrichosis — the illness caused by a Sporothrix infection — is rare in the U.S., but not unheard of. It’s generally picked up through contact with sharp plants that can pierce the skin like rose thorns, which is how it earned the moniker “rose gardener’s disease.” Sporotrichosis tends to cause a skin infection that’s very slow to heal, but it isn’t contagious, according to the CDC.
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When cats are infected, however, they carry a very high fungal load, meaning their wounds have a higher risk of spreading the infection to other cats, dogs and people, said Ian Hennessee, an epidemic intelligence service officer at the CDC and the lead author of the report.
“They get these awful wounds on their face, in their nasal cavities and on their paws, and those lesions are full of these fungi,” Hennessee said.
Usually, the infections don’t rise to a level of concern among public health officials.
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“The only reason this particular case came to the attention of the health department was because of the human involvement,” said Dr. Erin Petro, a state public health veterinarian at the Kansas Department of Health and Environment in Topeka. “That piqued our interest.”
The first case was in an indoor-outdoor cat who had a wound on her paw that didn’t heal with antibiotics. She spread the infection to a veterinary technician through a scratch, puncturing the tech’s glove and the skin beneath. Several months later, a second cat from the same household also got sick.
Neither the first cat nor the vet tech were immediately diagnosed with the fungal infection, delaying how quickly they were given antifungal drugs. The vet tech was put on an antifungal for eight months and her infection cleared. The first cat also got an antifungal, but she eventually got sicker and her owners had her euthanized. The second cat was treated much faster and recovered.
“The good news is that this fungal infection is treatable and cats can be cured if a diagnosis is made early,” said Dr. Arturo Casadevall, a microbiologist and chair of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, who was not involved with the report.
However, he added, “these infections take a long time to get better.”
The Kansas Department of Health and Environment suspects there was at least one other cat on the property that was infected, a stray cat with face lesions that died on the property but was not tested.
Sporothrix in Brazil
Most infections in cats, and sometimes dogs, end like the second cat’s story, Petro said: “They get treated and it goes away.”
What’s more, S. schenckii infections are rarely spread by cats.
That’s not the case in South America, where the S. brasiliensis species is much more contagious.
That species spreads rapidly among cats and has been known to infect people who were simply around infected cats, but did not come into contact with any wounds. According to Hennessee, these cases may have been due to the fungus being on surfaces and a person touching those surfaces and then their eyes or noses, but that is unclear.
The fungus was discovered in southeastern Brazil, but has since spread to other countries in South America. From 1998 to 2016, more than 4,500 human cases, contracted from cats, were reported, the CDC says.
The cases in Kansas raised concerns that S. braziliensis could be the culprit, but testing revealed it was the other species.
“We are not sounding the alarm that Sporothrix schenckii is nearly as much of a concern as Sporothrix brasiliensis,” Hennessee said.
“We know it’s a possibility that we could one day see Sporothrix brasiliensis cases in the U.S.,” he said. “We want to raise awareness without making folks too alarmed.”
Petro expects there are many more S. schenckii infections that occur every year that don’t get attention, either because the fungal infection isn’t reported, or because it isn’t diagnosed in the first place.
Most fungal infections in the U.S. are unreportable, meaning the CDC doesn’t keep track of how many cases there are. Sporotrichosis is among them.
“There is a big problem with fungal diseases but they tend to run under the radar,” said Casadevall.
Hennessee said the report is meant to raise awareness among veterinarians and pet owners so cases of sporotrichosis can be caught before they spread between cats or jump to people. But the infections are still thought to be rare and not serious in the U.S.
“If you have an outdoor cat that has a lesion that has not healed, you should at least ask their veterinarian if it could be a fungus,” Casadevall said. “You have to think about it.”
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