A deadly fungus that can infect cats and people is spreading

Host: Microbiologists are used to scary statistics, but a recent CDC presentation on a deadly fungus spreading through South America has experts genuinely horrified. Guest: What kind of fungus is causing that level of panic? Host: It’s called Sporothrix brasiliensis, and it causes severe, oozing skin ulcers in cats, dogs, and humans. Guest: How is it jumping between animals and people so easily? Host: It spreads through the scratching, biting, or even grooming of infected cats, which has led to a massive, ongoing outbreak. Guest: Just how widespread is this outbreak right now? Host: Since emerging in Brazil in the 1990s, it has killed thousands of cats and infected over eleven thousand people across multiple South American countries. Guest: If it's mostly in South America right now, is the U.S. at immediate risk? Host: Yes, a CDC expert warned it's just a matter of time before it reaches the U.S., because all it takes is one traveler bringing an infected cat with them. Guest: I imagine areas with a lot of stray or outdoor cats would be especially vulnerable if that happens. Host: Exactly, which is why officials are deeply concerned about major cities with large street cat populations, as well as U.S. rural areas where farm cats roam freely.

Host: Let's look at what Sporothrix brasiliensis actually does when it infects an animal. In cats, it starts by causing terrible oozing skin ulcers and swollen lymph glands. Guest: That sounds incredibly painful, but is it something a vet can treat? Host: It is actually very dangerous, because without antifungal drugs, the infection spreads to the lungs and is 100 percent fatal for cats. Even with treatment, a large number of infected cats still do not survive. Guest: What happens if an infected cat passes the fungus on to a human? Host: Humans also develop painful skin ulcers, and the disease can be deadly for anyone with a weakened immune system. What makes containment really complicated is that symptoms can be delayed for a surprisingly long time. Guest: How long can the infection hide before someone actually realizes they are sick? Host: In one case, a family moved from Brazil to the UK and did not develop symptoms until three years later. It turned out one of their cats was secretly carrying the fungus all along, and even the British vet who eventually treated the animal got infected. Guest: That is terrifying, so what makes this specific fungus so adaptable and contagious? Host: Like some other soil-dwelling fungi, it is dimorphic, meaning it literally shape-shifts. One researcher perfectly described this by saying it is a mold in the cold, and a yeast in the beast. Guest: So it grows as long mold filaments out in the soil, but transforms into single-celled yeast once it gets inside a warm animal? Host: Exactly, but here is its real superpower, because Sporothrix brasiliensis can actually spread directly from host to host while it is in that yeast form. Most fungal infections only happen when you interact with environmental spores, so this direct yeast transmission is completely unique.

Host: This fungus, Sporothrix brasiliensis, is actually a bit of a shapeshifter. In the soil, it grows as long threads, but once it gets inside a host's body, it transforms into a single-celled yeast. Guest: Usually fungi spread when we inhale environmental spores, so how does this yeast form spread between hosts? Host: That is exactly what makes this fungus so unusual, because its yeast form is highly contagious. Normal cat behaviors, like fighting, biting, or even affectionate grooming, act as the perfect delivery system. Guest: I imagine that's a nightmare for an owner who just wants to care for their sick cat. Host: It really is. Experts believe half of all human cases happen when owners get scratched or bitten while trying to force medication down their infected cat's throat. But direct contact isn't the only risk, because these cats can also sneeze out the infectious yeast. Guest: Wait, they sneeze out the fungus? How long can it survive on a surface after the cat leaves the room? Host: A remarkably long time. In lab tests, it survived on stainless steel surfaces, similar to veterinary exam tables, for up to ten weeks. Guest: Ten weeks! Is there any way for a vet clinic to safely get rid of it? Host: Thankfully, simple bleach and ethanol easily kill it. The bigger issue right now is detection, because there isn't a commercial test for it yet. Guest: Since there's no test, how are we screening cats that travel internationally? Host: We really aren't, as cats entering the US currently just need a standard certificate from a vet saying they appear healthy. That makes the disease incredibly easy to miss. Guest: So an infected cat could easily slip across the border if it isn't showing obvious symptoms yet. Host: Precisely. That's why public health officials are urging veterinarians to be on high alert and report any suspicious cases to the CDC, so we can stop it from establishing itself in the US.