The fungus discovered in Brazil that spreads and is already worrying scientists

Until the mid-1990s, the fungus Sporothrix brasiliensis he was a illustrious stranger. Suddenly, however, it became a public health problem.

The first cases of infection by this pathogen began to draw attention in Rio de Janeiro, where researchers observed that transmission occurred mainly from stray cats.

Soon, the infections spread to other Brazilian states.

A few years later, circulation of the microorganism was detected in Argentina, Paraguay, Bolivia, Colombia and Panama, with specific cases also registered in England and the United States.

But what explains this spread? Behind this little-known epidemic lies an example of how an imbalance in the environment can lead to surprising and unexpected consequences.

From harmless to menace

Fungi of the genus Sporothrix they have been known since 1898. They appear mainly in the soil and on some plants.

Just like their cousins ​​that belong to the same kingdom, these species are fundamental to decomposing organic matter in nature.

In some rare cases, however, these microorganisms can cause diseases in humans, known generically as sporotrichosis.

O Sporothrix brasiliensis, for example, manages to infiltrate the superficial layers of the skin. The pathogen colonizes this subcutaneous tissue and causes wounds.

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

As mentioned earlier, these cases were rare. But their frequency began to draw attention in the late 1990s in some locations in Rio de Janeiro.

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

“Of the 178 patients, 156 had some contact at home or at work with cats that also had this disease, and 97 were bitten or scratched by these animals”, describes the work.

That was one of the first clues that caught the attention of specialists: for some reason, the numbers of the disease were growing little by little.

“According to the latest statistics, there have been more than 12,000 cases in human beings since then”, updates doctor Flavio Telles, from the Brazilian Society of Infectious Diseases.

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

Over time, researchers were able to better understand the cycle of infection not only among people, but also in animals that live close to our homes.

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

“And an infected cat transmits it to others, as well as dogs and humans.”

“This is because physical disputes in the search for territories, food and mating are part of feline biology, in which one animal bites and scratches the other”, he adds.

Let it be clear: cats are not to blame for sporotrichosis. They are just as victims as dogs and people – and the lack of public policies to control the spread of the fungus allowed it to spread, reinforce the sources heard by BBC News Brasil.

But why has this situation become a problem starting from Rio de Janeiro during the last few years?

Environmental imbalances

Microbiologist Marcio Lourenço Rodrigues, from FioCruz Paraná, clarifies that the rise of Sporothrix brasiliensis is still the subject of studies and speculation.

“Why was he already there on the ground and, all of a sudden, it became a public health emergency?”, he asks.

“There is a direct association between this fact and land occupation, deforestation and housing construction. That is, you start to have a disorganization of ecosystems that were previously in balance and this exposes animals and human beings to new pathogens”, complete.

Once the fungus arrived in wild and stray cats, the “leapfrog” to humans was relatively easy. After all, these felines are extremely common in many Brazilian neighborhoods.

Not infrequently, children play with them and adults welcome having them around as a way to control rat infestations.

That is, the whole context of environmental imbalance added to the proximity to animals facilitated contact with the fungus, which started to cause the disease in thousands of people in the last two decades.

While these observations help explain how the outbreak caused by the Sporothrix brasiliensis emerged, they do not allow us to understand how the problem spread to places other than Rio de Janeiro.

In Argentina, for example, 0.16 new cases of feline sporotrichosis were detected per month in 2011. In 2019, that rate was 0.75 cases —a growth of more than four times in less than a decade.

“Cats transit through a territory and can cross dry borders of states or even countries”, says Telles.

“In addition, they can be transported by people who move from neighborhood or city”, he adds.

Another possible explanation for the spread of Sporothrix brasiliensis across several countries in the Americas is in rats.

Some studies show that these rodents can also carry the fungus — and go from place to place while transporting food by trucks or ships.

In a new location, mice are hunted by the cats that live there. Felines, in turn, end up becoming infected and start a new cycle of sporotrichosis.

To complete, as these animals carry the fungus in their claws, saliva and blood, they can transmit it to humans through bites or scratches.

What to do?

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

Treatment is also not the easiest: not always the antifungal remedies available work at first.

Drug therapy usually lasts, on average, 187 days, calculates a recent study by the Federal University of Rio Grande (FURG).

The key, guarantee other articles published in recent years, is making the correct diagnosis and starting treatment as soon as possible.

This even prevents the creation of drug resistance — this, by the way, has been a frequent problem in recent years with other species of fungi, which are becoming increasingly difficult to combat.

For Rodrigues, cases like that of Sporothrix brasiliensis reveal how imbalances in the environment caused by human action have unpredictable consequences.

“15 years ago, sporotrichosis was not a problem. The alteration of ecosystems provides possible exposure to pathogens that, before, did not happen”, he says.

“And this generates public health crises that are increasingly difficult to face”, he adds.

Telles understands that the episode reinforces the importance of facing human health, animals and the planet itself as a single thing.

“We are talking about a complex issue, which depends on a global approach. We will need doctors, veterinarians, epidemiologists, microbiologists, sanitarians, environmentalists and a series of other professionals to deal with this and other similar crises”, he concludes.