(CNN Spanish) – The video game and subsequent series “The Last of Us” makes its users wonder if such a situation could happen in real life.
In the series, which airs on HBO Max — part of Warner Bros. Discovery, parent company – The Cordyceps fungus is transmitted from human to human through a bite, turning its host into a fast and aggressive zombie. In real life, fungi only affect insects.
Dr. Huerta goes into detail in this episode. The office is open, you are welcome!
You can listen to this episode on Spotify or your favorite podcast platform, or read the transcript below.
Hey, welcome to this new episode of In Consultation with Dr. Elmer Huerta, your favorite health podcast on CNN en Español. Dr. Huerta welcomes you, I hope you are well.
“Zombie mushrooms”: from the real world to science fiction
In today’s episode, we will study some scientific aspects related to the so-called “zombie fungi” and other microorganisms that have the ability to change the behavior of the hosts that infect them.
If you are a fan of TV series, you may have recently paid attention to a series called “The Last of Us” which can be loosely translated as “The Last of Us”.
The nine-episode HBO Max series is a film adaptation of the online game of the same name created in 2013. The production describes life in a terrifying world where humanity was nearly wiped out after an epidemic caused by a fungus.
In the series, people infected with the fungus are transformed into a type of aggressive zombie in which the fungus grows inside of them. They try to bite others to infect them.
The interesting thing about the series, and the reason for making this episode a science and medicine podcast, is that the mushroom in question—called Cordyceps—is real.
It has long been known that it is capable of infecting various types of insects. It has been proven that this mushroom changes its behavior after growing inside it, which is why it was called the “zombie mushroom”.
We must clarify that experts agree that infection with this fungus has not been recorded in humans. This is unlikely to happen due to the huge difference between human and insect anatomy.
However, it is interesting to study the mechanism by which fungi alter the behavior of insects, because some of the chemicals in the fungi could have applications in medicine.
What mushrooms cordyceps?
mushrooms cordyceps They form a family of dozens of species that are consumed as food by some Asian cultures and have been studied extensively for the type of infection they cause in carpenter ants.
Ants are infected by fungal spores in the environment that grow inside their bodies within 24 to 48 hours and spread within two to three weeks.
According to Rebecca Rosengaus, associate professor of marine and environmental sciences at Northeastern University, the fungus produces neurotoxins, or neuromodulators, that alter the insect’s neurobiology, essentially turning it into a zombie.
Similarly, entomologist David Hughes, who served as a consultant on The Last of Us, says the fungus surrounds the insect’s muscles, affects its motor neurons, and turns it into a puppet.
The effect of these fungi on ants
This change in ant behavior is extraordinarily surprising, because at a certain moment of infestation, the zombie ant is looking for a branch exactly 25 cm away from the ant colony. Upon reaching this point, which is supposed to have the most suitable temperature and humidity for the development of the fungus, the ant sticks its jaws into the vein of the leaf and anchors itself in that place, observing later a shocking scene that appears to be from science fiction.
Little by little, from the ant’s head, mushrooms begin to emerge. cordyceps. A kind of worm with enlarged ends can be seen like a fruit filled with seeds. From there come the thousands of spores that fall on the ant colony located below the dead ant to infect it, or that are carried by the wind to infect other distant colonies.
The intelligence of the ants is such that workers are constantly watching for the presence of zombie ants. “Zombies” are recognized because – when infected – they acquire antisocial behavior, very different from that of other members of the colony. When they are identified, the workers will drag the infected ants away from the colonies to die there and thus avoid infection.
This natural event has been thoroughly documented and studied. Having seen, as we have said, that fungi contain various chemical compounds, including nucleosides, cyclic peptides, sterols, flavonoids, alkaloids and various sugars, through which they will affect the affected insect.
One of those substances found in the zombie mushroom, cordycepin – which is chemically an analog of a nucleoside – is being studied in the laboratory to determine its use in human medicine.
Cordycepin and its use in humans
In this regard, in a study published in the journal particles As of September 2021, British researchers have conducted a comprehensive review of the medical literature on the properties of cordycepin.
After identifying 1,204 publications, the researchers determined that 791 were of sufficient quality to be considered in the review. In 150 animal studies, they determined that cordycepin showed some potential therapeutic effects. These include:
- tumor growth reduction in 37 articles,
- pain and inflammation decreased in 9 articles,
- protecting brain function in 11 articles,
- improved respiratory and cardiac functions in 8 and 19 articles, respectively,
- and improved metabolic disorders in 8 articles.
The authors concluded that because the mechanism of action of cordycepin and the manner in which this substance is distributed in the body is unknown, it is still too early to be optimistic; However, it deserves further investigation.
By the way, during the epidemic, cordycepin was studied as a potential treatment against SARS-CoV-2, both for the properties of inhibiting the replication of the virus, and for the potential protective effect on the brain and lungs during Covid-19.
The fact that a chemical derived from a strange zombie mushroom can be beneficial to humans shouldn’t attract attention.
Let’s remember that psilocybin and LSD – hallucinogens that have been studied extensively in recent years for the treatment of depression and other mental health disorders – are chemicals derived from mushrooms. Similarly, the antibiotic penicillin, which was accidentally discovered by the Scottish bacteriologist Alexander Fleming in 1928, is also a by-product of fungi, Penicillium notatum.
What other factors change behavior in animals?
But fungi are not the only microorganisms causing behavioral changes in animals.
It has long been known that the parasite toxoplasmawhich multiply in the intestines of cats, have strange properties when they infect mice.
Apparently an injured mouse toxoplasma He develops brain lesions that completely alter his behaviour. This happens through an inflammatory mechanism, although it could also be through chemicals or an immune reaction.
Usually, rats are very wary, wary, and fearful animals that flee from certain environments and odors that may indicate a danger to their safety.
But surprisingly, mice are infected toxoplasma They lose that fear and become very curious. They lose their fear and are exposed not only to cats, but to many other animals that eat them.
It is believed that this change in the behavior of rats will be intended for toxoplasma Other animals, especially cats, can also infect animals that breed in their intestines.
It is precisely because of these types of observations that it has been hypothesized that schizophrenia may be related to infection by toxoplasma .
the toxoplasma And schizophrenia.. Is there a relationship?
Although there are more than 100 studies linking infection with it toxoplasma With schizophrenia, given the rarity of this disease, it is very difficult to study this association and conclude that there is a cause-and-effect relationship.
This is particularly difficult because it is complex to show that infection with it toxoplasma precedes the diagnosis of schizophrenia.
However, a study published in 2019 of more than 80,000 blood donors in Denmark found that the risk of developing schizophrenia was 2.7 times higher in people who had it before the onset of the disease.
Although the relationship between toxoplasmosis and schizophrenia is still not conclusively clear, human toxoplasmosis is a real disease, capable of causing multiple complications in the body, especially in pregnant women, as it can cause premature birth and cause blindness and mental retardation in children. . .
Prevention consists in periodically examining our cats, especially if we let them out of the house. Cats get it toxoplasma By eating contaminated food outside the home.
In short, with cinematic license to remove the scientific truth from fungi spreading through spores (they changed it to bites), “The Last of Us” has some real science stuff, made for us thinking about the delicate and often unknown balance between organisms that live on the planet.
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