Zombie Apocalypse Now –the Cordyceps Fungus

Winner of the 2023 Cheltenham Muscat Biology article contest

by Luciana Jaramillo-Ruiz

‘Frankenstein’...fiction. ‘World War Z’...fiction. ‘The Girl with All the Gifts’...fiction.

One thing that all these texts have in common is that they include gruesome, undead, corporeal revenants, otherwise known as zombies. But of course, these aren’t real.... or are they? We all love horror books, movies, and tales; especially ones that include zombies, but the question is, are zombies really real?

Well, technically...yes.

How the fungus turns its prey into ‘zombies’

The Cordyceps fungus, better known as the zombie ant fungus, infects insects such as ants or spiders. The fungus is found in southeast Asia, and it has over 400 variations that can be found worldwide. Like any other parasite, the Cordyceps fungi clears out the host’s nutrients before filling its body with spores that later allow it to reproduce. Noticeable actions prove that the fungi are infiltrating the host such as twitching, behaving erratically and irregular timed full body convulsions.

The fungi then compel its host to quest for an area of height where the temperature, humidity and sunlight is ideal. This process is called summiting. The fungi force its prey to perform a ‘death grip’ or a ‘death pose’ which causes the host to stay in a certain fixed position for an extended period. When the fungus is ready to reproduce, the fungi takes in its real form and ‘sprouts’ out of the hosts head revealing a tendril shooting its spores out, after some time infecting other insects matching the hosts species. This process takes about 4-10 days (about one and a half weeks).

When these spores are shot out, they are likely to land on a new host or prey, which become the next generation of killer fungi. Think of them as being terrorists (albeit without a political agenda – hopefully) because that’s exactly what they do to the ants’ population, terrorise them! The process of spores being shot out continues for hours. If the Cordyceps succeeds but lands on the insect’s wing (where it can’t bore into) it will shoot out secondary spores to increase the risk or chance of the Cordyceps brain washing its next prey. The Cordyceps deadly spores are very fragile and this oppressive puppet master only does what it needs for its own survival.

Can the ‘zombie fungus’ threaten humans?

Now the moment we’ve all waited for, can this parasitic fungus take over the human body? No. I bet that’s what you wanted to hear before you went to sleep. The Cordyceps fungi can’t infect human beings due to our high body temperatures and our complex immune systems which are harder to take over compared to those of an ant or an insect. Due to this, our immune system is highly efficient at destroying spores. In this case, the Cordyceps fungi, as one gets infected when the Cordyceps spores enter the hosts body. Our innate immune system plays a key role in keeping pathogens (bacteria, virus fungi or other harmful microorganisms) out of our body by identifying the infected cells with pattern recognition receptors (PRRs) and destroying them through specialised cells. There are thousands of Cordyceps species each designed to infect a particular species, thankfully we aren’t on their hit-list.

A Cordyceps infected ant

Although our human bodies are more resistant to Cordyceps than those of an ant or spider, that does not mean we are free from fungi assailing our bodies. One of these examples is ergot poisoning otherwise known as ‘St. Anthonys fire’ or ‘Holy fire’. Ergot poisoning, or ergotism, is caused by eating food (typically rye) contaminated with a fungus called C. purpurea. The popular show: ‘The Last of Us’, took inspiration from the Cordyceps fungi. In the show the Cordyceps can infect both humans and animals, it is also transmitted through food supplies which is somewhat like what the ergot poisoning does.

What use does the Cordyceps have?

The Cordyceps fungi plays a particularly vital role in the jungle’s diversity (where the Cordyceps fungi is mostly found). In most ecosystems, top predators are important in controlling their prey diversity, regulating lower species in the food chain. This is similar to what the Cordyceps does in the insect population. The parasite stops any group of insects from getting the upper hand, in this case, gaining an advantage via overpopulation. If any insect species overpopulates in the jungle or its habitat, they have a higher chance of becoming this puppeteer’s next marionette.

Unbelievably, the Cordyceps fungi has been used as traditional Chinese medicine for a long time. Although the Cordyceps is a fungus, the type of Cordyceps grown in labs, later produced transformed into medicine, isn’t a mushroom. People often

References

David Attenborough, 3 Nov 2008, Cordyceps: attack of the killer fungi - Planet Earth Attenborough BBC wildlife, BBC Studios, 4/13/2023, https://youtu. be/XuKjBIBBAL8

Ed Yong, Nov 14 2017, How the zombie fungus takes over ant’s bodies to control their minds, The Atlantic, 4/12/2023, https://www.theatlantic.com/ science/archive/2017/11/how-the-zombie-fungus-takes-over-ants-bodies-tocontrol-their-minds/545864/

Youri Benadjaoud and Dr. John Brownstein, February 5, 2023, the science behind the ‘zombie fungus’ from the last of us, ABC news, 4/10/2023, https:// abcnews.go.com/Health/science-zombie-fungus-us/story?id=96819243 use the Cordyceps as a medicine for coughs, CKD (chronic kidney disease), ringing in the ears, immunosuppression after organ transplant and more. Although Cordyceps is generally safe, it may sometimes have negative side effects including an upset stomach, nausea, and dry mouth in some people.

Wildlife can be cruel, grotesque and fascinating. Humans have barely scraped the surface in understanding what the cohabitors of our planet can do. Despite the advances that science has made over the past century, our understanding of nature is still far from complete. Afterall, who knew a parasitic puppet master hijacks insects that live among us? We like to believe that our mind is of our own and that we dominate our thoughts and actions, but is this always true? These infamous parasites’ methods of mind controlling are more complex and sinister than anyone could have reckoned. Next time you feel eccentric, or start twitching, who knows, you might be next...

Interested in learning more?

Here’s a video you may enjoy:

Mike Hume, January 15 2023, ‘The Last of Us’ zombie fungus is real and its found in health supplements, The Washington Post, 4/09/2023, https://www. washingtonpost.com/video-games/2023/01/15/last-of-us-hbo- cordyceps/ Jennifer Lu, April 18 2019, How does the parasitic fungus turn ants’ into ‘zombies’, National Geographic, 4/10/2023, https://www.nationalgeographic. com/animals/article/cordyceps-zombie-fungus-takes-over-ants