From Antibiotics to Zombies: Killer Fungi in Folk Medicine and Modern Media

Cordyceps is a group of entomopathogenic (insect-killing) fungi. Although there are many different kinds of fungi that can kill insects through opportunistic infection, Cordyceps and its relatives are specialists that infect specific insects as a necessary part of their life cycle. A spore that lands on a compatible host germinates and penetrates the exoskeleton; after it kills the insect and drains the body of nourishment, an elaborate fruiting body sprouts from the corpse and disperses more spores on the wind.

A Cordyceps sensu lato fungus infects bullet ants, Paraponera clavata. During the course of infection, this particular species, like many parasites and pathogens, induces a behavioral change in its host, causing the ant to climb upwards and clamp onto the substrate before killing it.

The fruiting bodies of at least one species, analogous to the fruiting bodies of regular mushrooms, has been prized for centuries in traditional Chinese medicine. The caterpillar fungus Ophiocordyceps sinensis is found only in certain localities on the Tibetan Plateau, where it infects the caterpillars of ghost moths in the family Hepialidae. In recent years, demand for the fungus has expanded from local markets into a newly affluent and cosmopolitan China, causing prices to skyrocket tenfold or more. Whole fortunes and corporate empires are being built on the export of this fungus, but even as local Tibetan gatherers have been able to afford new livelihoods with this influx of wealth, the overharvest is sowing discord among communities competing for access to the increasingly scarce patches where the fungus can still be found.

The prized caterpillar fungus, Ophiocordyceps sinensis. By Daniel Winkler, from NPR.
The prized caterpillar fungus, Ophiocordyceps sinensis. By Daniel Winkler, from NPR.

In a medical belief system that has embraced Western biomedicine, caterpillar fungus is now touted for curing various ailments, fatigue, aging, cancer, and sexual dysfunction. Whether these claims have any truth to them remains mostly untested with rigorous science in the West, but the compounds of other Cordyceps fungi have been studied as early as 1950 for their antibiotic, antioxidant, and other pharmacological properties. Notably, the drug ciclosporin A, used for decades to suppress immune system attack on organ transplants, was originally isolated from the mold Tolypocladium inflatum, the nonparasitic, asexually reproducing form of a Cordyceps fungus.

Cordyceps militaris, another caterpillar fungus, and the original source of the drug cordycepin. By Ak ccm, from Wikipedia.

Lest you might think that Cordyceps fungi are significant only in exotic Far Eastern cultures, it should be pointed out that the parasitic fungus has also made its mark in American pop culture. With the rise in popularity of zombie tropes in movies, television, and video games, the way in which Cordyceps manipulates its host’s behavior to increase the transmission of its spores has inspired plotlines in which diseases create zombies and spread by inducing a taste for healthy human flesh in their victims. While it’s not any time soon that Cordyceps will either turn us all into the undead or provide civilization with the next historic medical breakthrough, it is nonetheless an interesting example of science that is being infused with modern popular culture on one hand, and ancient folk tradition on another.

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