Sporothrix brasiliensis: why a fungus transmitted from cat to human is of concern in Latin America

The mushroom Sporothrix brasiliensis he was virtually unknown until the mid-1990s.

But it has since become a public health problem in Latin America because it causes severe skin lesions in cats and humans.

The first cases of infection by this pathogen were discovered in Rio de Janeiro, where researchers discovered transmission from feral cats to humans.

Infections quickly spread to other Brazilian states.

A public hospital in Sao Paulo saw an increase in cases over a 15-year period, according to a study published in September in the journal of the Brazilian Society of Dermatology.

“We used to see one or two cases a year,” said Dr. John Verrinder Veasey, one of the authors, told the medical news portal fellowship.

‘Now we find them two or three times a weekhe added.

In December, Brazilian dermatologist Rossana Sette published images of skin lesions caused by an infection of Sporothrix.

The patient indicated that there were cats in his workplace.

It has also been found that the Sporothrix brasiliensis circulates in Argentina, Paraguay, Bolivia, Colombia and Panama.

But why this spread?

Behind this little-known epidemic, we find an example of how an environmental imbalance can lead to unexpected consequences.

From innocent to threatening

The fungi of the genus Sporothrix they have been known since 1898. They are mainly found in the soil and on some plants.

Like other fungi, they are essential for the breakdown of organic matter in nature.

A vet posted a photo of an infected cat.

In an unusual way, these microorganisms can cause disease in humans, commonly known as sporotrichosis.

He Sporothrix brasiliensis it infiltrates the superficial layers of the skin, colonizes the subcutaneous tissue and causes wounds.

The fungus can too invade the lymphatic system and affect the eyes, nose and even the lungs.

As we mentioned earlier, these are rare cases.

However, the increased frequency began to receive attention in some parts of Rio de Janeiro in the late 1990s.

contact with cats

Between 1998 and 2001, researchers at the Oswaldo Cruz Foundation (FioCruz) diagnosed 178 cases of sporotrichosis.

“Of the 178 patients, 156 had had some contact with infected cats at home or at work, and 97 received bites or scratches from these animals,” the researchers wrote.

Since then, the numbers have grown exponentially.

“According to the latest statistics, there were more than 12,000 human cases” noted Dr. Flavio Telles, of the Brazilian Society of Infectious Diseases.

“And that’s not counting the countless records in cats and dogs,” he added.

Over time, researchers have come to better understand the cycle of infection between humans and animals living close to home.

“For some reason, the fungus has adapted to cats. In them, the pathogen causes a disseminated disease, which causes wounds on the face and legs,” explains Telles, who is also a professor at the Federal University of Paraná.

“This is because the physical disputes in search of territories, food and mating they are part of cat biology, with one animal biting and scratching another,” he explains.

Experts interviewed by the BBC believe that cats should not be blamed for the spread of sporotrichosis.

Like dogs and people, they are victims; and the lack of government policies to control the fungus allows it to spread.

environmental imbalances

Microbiologist Marcio Rodrigues, of FioCruz, acknowledges that the rise of Sporothrix brasiliensis It is still the subject of studies and speculation.

“There is a direct link between the increase in cases and land occupation, deforestation and housing construction,” he claimed.

He argued that there is “a disruption of ecosystems that were previously in equilibrium, and this exposes animals and humans to new pathogens.”

After infecting stray cats with the fungus, the jump to humans was relatively easy, as these felines are abundant in many Brazilian neighborhoods.

Children often play with it, and adults Thank you keep animals close by as a way to control rat infestations.

The context of an unbalanced environment combined with the proximity of the animals favored contact with the fungus, which began to infect humans.

While these observations help explain how the outbreak of Sporothrix brasiliensisdoes not make us understand how the problem spread beyond Brazil.

Argentina

For example, in Argentina cases of feline sporotrichosis quadrupled in less than a decade since 2011.

“Cats can cross state or even country lines,” says Flavio Telles.

“In addition, people who move out of the neighborhood or city can transport them,” he added.

rats

Another possible hypothesis about the spread of Sporothrix brasiliensis in several countries of America it has to do with rats.

Some studies indicate that these rodents may also carry the fungus.

And these animals can easily move from one place to another as “clandestine travelers” in food transports by land or sea.

At the new location, the cats living there hunt the rats.

These cats become infected and start another cycle of sporotrichosis.

What can we do?

Compared to other fungi of the same genus, the Sporothrix brasiliensis it is more virulent (meaning it spreads more easily) and can cause more serious infections.

Treatment is also not easy: available antifungal drugs may not be effective at first.

and drug therapy usually lasts an average of 187 daysaccording to a recent study by the Federal University of Rio Grande (FURG).

The key is to get the right diagnosis and start treatment as soon as possible.

This also prevents the formation of drug resistance in humans, a common problem in recent years with other fungal species.

The impact on the environment

For Marcio Rodrigues, things like the Sporothrix brasiliensis they reveal the unpredictable consequences of environmental imbalances caused by human actions.

Sporotrichosis That wasn’t a problem 15 years ago”, says the microbiologist.

“The change in ecosystems is generating potential exposures to pathogens that were previously unheard of, and this is causing a public health crisis,” he says.

For Telles, this issue highlights the importance of seeing human, animal and planet health as a whole.

“We are talking about a complex issue that depends on a global approach,” he explains.

“We need doctors, veterinarians, epidemiologists, microbiologists, health professionals, environmentalists and many other professionals to deal with this and similar crisis.”