Mushrooms will replace viruses

(ORDO NEWS) — One of the most unexpected and dangerous consequences of global warming can be the massive spread of disease-causing fungi. Over time, fungal epidemics can be no less dangerous than viral ones.

Sooner or later, fungi will get our bodies, but as long as we are alive, they do not seem to be such a serious threat. Fungal infections are rare and even less likely to be something more serious than itching on infected areas of the skin or mucous membranes.

They are only dangerous for people with severely weakened immunity – after chemotherapy or because of HIV. So far, this threat cannot be compared with a viral or bacterial one, but in the future the situation may change. And it seems to be changing now.

In 2009, Japanese doctors reported a unique case of a fungal infection caused by a previously unknown fungus that was found to be resistant to most drugs used against such infections. Candida auris cells were isolated and described from the ear canal of a 70-year-old patient.

Since then, outbreaks of new candidiasis (the so-called diseases caused by fungi of the genus Candida ) have been recorded in dozens of countries, including India and China, the EU and North America, Australia and South Africa. From one to two thirds of those infected cannot be saved .

It could be assumed that these microbes are carried along with travelers and cargo. However, sequencing of different strains has shown that they originated in different parts of the world independently and almost simultaneously. What is actually happening?

Coldblooded killer

Mushrooms will replace viruses 2A frog that died from chytridiomycosis Forrest Brem (Virginia Gewin, PLoS Biology, 2008)

Between the different “branches” of life, very peculiar connections have developed. Humans and other mammals have a “special relationship” with bacteria: without some we can barely survive, while others turn out to be dangerous pathogens.

But plants coexist in a similar way with fungi. With some, they form close and mutually beneficial partnerships, developing soil resources. Other fungi threaten them with extremely serious diseases. Such infections are widespread among some animals, including fish, amphibians and reptiles.

Today, the world is facing a pandemic of the fungus Batrachochytrium dendrobatidis , which causes highly lethal chytridiomycosis in frogs and other amphibians.

For the first time this danger was realized only in the late 1990s, and by now the disease has sharply reduced the number of every third (more than 500) of all amphibian species, and some (up to 90) have completely destroyed.

However, for humans and other mammals, chytridiomycosis is completely harmless, and the reason for this is simple: temperature.

The fact that fungal infections in our country mainly affect the mucous membranes and skin is not only due to the fact that they are the first to come into contact with the myriad of microscopic spores that fill the air and water.

The human body inside is too warm for them. In the same year 2009, when Candida auris was isolated in Japan , American scientists tested the temperature tolerance of thousands of strains of fungi, showing that each additional degree of temperature (when it increases between 30 and 40 ° C) makes the environment unfavorable for about six percent of them. At a normal human body temperature of 36.5-37 ° C, about 95 percent of fungi do not survive.

Temperature shield

Mushrooms will replace viruses 3Lesser brown bat affected by “white nose syndrome”

This effect is especially pronounced during periods of hibernation – hibernation, which some mammals fall into. At the same time, the heartbeat, respiration and metabolism slow down dramatically, immunity decreases, and body temperature drops dramatically, making the animal more susceptible to fungal diseases.

It is not for nothing that perhaps the only widely known example of such an epidemic among mammals is the “ white nose syndrome ”, which destroys millions of bats, mainly those that hibernate.

Scientists examine their corpses without much fear: the fungi that cause the syndrome, Pseudogymnoascus destructans , are active at temperatures close to zero and are not afraid of people.

There is even a hypothesis according to which warm-bloodedness in animals appeared, first of all, as a means of defense against fungal infections.

Maintaining a high body temperature is an extremely costly task, and a mammal often has to find and consume as many calories daily as a reptile would have for a month. And yet, it can be beneficial, if only because of the protection that heat provides.

Mushrooms are not very temperature tolerant. They do not tolerate both heat and cold, and a change of several degrees relative to their usual range can be deadly for them. But, like other living beings, they are changeable and subject to environmental pressure, adapting and surviving in a variety of conditions.

And global warming can stimulate them to adapt to higher temperatures. Each additional degree reduces the effectiveness of the “temperature shield” by a few percent, gradually undermining our defenses. And scientists predict such a development of events for more than a year. But, as with global warming itself, they are little heeded.

Mushrooms will replace viruses 4Countries marked in blue on the world map where Candida auris has spread

There is no big doubt that the spread of Candida auris , which causes a dangerous infection, is partly “guilty” of global warming. No wonder strains isolated from patients survive at higher temperatures (up to a feverish 42 ° C) than their less dangerous relatives.

Already today, such candidiasis is diagnosed in millions of patients around the world, and the annual mortality from them, according to some estimates, exceeds 160,000 C. auris is resistant to most antifungal drugs and can be treated only after a long enumeration of available funds – if doctors have enough time.

Due to the fact that the threat of fungal infections still cannot be compared with bacterial and viral infections common to people, the arsenal of means to combat them is far from being so great.

The search for new drugs is chronically underfunded, despite the fact that fungal cells are much more similar to animal cells than bacterial cells, which means that finding substances that would affect them, but not affect the patient’s body, is much more difficult than, for example, antibiotics that affect bacteria.

And if we do not address the problem now, then when (and if) fungi massively adapt to survive in the human body, it may be too late.


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