The ant is no longer master of its body. After crawling away from its colony, it hangs precariously from a leaf, awaiting death. This will come from a fungus, which devours the insect from the inside before breaking out of its skull to release spores into the air.
“They look like spooky Christmas ornaments hanging in the forest,” says Ian Will, a fungus geneticist at the University of Central Florida, where the undead ants can be found. With rising temperatures, fungal infections are likely to multiply.
A FUNGUS PARASITIC OF ANTS
While scientists have identified regarding 35 ophiocordyceps fungi capable of turning insects into living dead, there are, however, 600 species, explains Joao Araujoa specialist in parasitic fungi at the New York Botanical Garden.
Infected individuals initially exhibit erratic and abnormal behavior. According to scientists, the parasite takes physical control of its host by growing fungal cells around its brain. It then “hacks” the insect’s nervous system to control its muscles. Ian Will says researchers still don’t know if the fungus does this by releasing chemicals or altering the insect’s DNA.
This process the fungus has been perfecting on its specific host for a long time; we didn’t exist then.
“We think they have been evolving together for regarding 45 million years,” says João Araújo.
IS INFECTION POSSIBLE IN HUMANS?
In order to infect any other warm-blooded animal, the fungus will need to undergo significant evolution.
“Millions of years of genetic modification would be needed for it to really infect mammals,” says João Araújo.
Since each species of parasitic fungus has evolved to attack a particular insect, unique strains have little effect on other organisms. Thus, a cordyceps that has evolved to infect a species of ant living in Thailand will not be able to infect another species of ant present in Florida.
“If a jump from one species of ant to another is difficult, imagining a jump to humans is science fiction,” says Ian Will. But the idea that temperature plays a role in fungal infections makes a lot of sense.”
THE THREAT OF CLIMATE CHANGE
Even in the absence of an imminent threat from this parasite, many other fungi are to be feared.
There are millions of fungal species in the world and several hundred are dangerous for humans. Only the high temperature of our body protects us from serious fungal infections. 37°C is too much for most mushroom species. They generally prefer temperatures between 25 and 30°C to spread an infection.
(To read : The temperature of the human body would not be 37°C.)
“One of the reasons why we suffer from mycosis of the skin is that the fungi manage to penetrate between the folds of the skin. These are humid and dark areas, where fungi can proliferate, because the temperature is lower there than in our body, “explains Shmuel Shohaman infectious disease specialist at Johns Hopkins University School of Medicine.
“With the Earth warming up, our fear is that the temperature difference between the environment and our body will decrease,” he underlines. It would then be easier for fungi that have evolved to withstand the warmer outside temperatures to survive in our body.
Scientists believe they have identified a species of fungus capable of infecting humans that would have benefited from the rise in temperatures: it is White ears.
Unknown to the scientific world before 2007, it was suddenly discovered on three different continents in 2011 and 2012.
“She came out of nowhere,” says Arturo Casadevall, an infectious disease specialist at the Johns Hopkins School of Public Health. “It is believed that this fungus was already there and adapted to the higher temperatures over time until it broke through.”
Once present in the blood, the fungus induces symptoms similar to those of a bacterial infection, emphasizes Shmuel Shoham. People with a good immune system manage to eliminate it without difficulty. Others are less fortunate: according to the Centers for Disease Control, the death rate reaches 30 to 60% in patients infected with the fungus. However, it is difficult to determine the role White ears played a role in these deaths, since the possibility that the patients suffered from underlying health problems cannot be ruled out.
Could a fungal outbreak similar to COVID-19 be possible? For Arturo Casadevall, nothing is excluded.
Contemplating this possibility, he says: “Am I worried regarding the emergence of an unknown disease that will infect immunocompetent people? Sure. »
