Real-life zombies don’t only exist in video games, but it’s not what you think
By: Kirsten Diamond
Tags: Nature, Biology, Science, Gaming, Education

A fungus that infects and slowly moves through the body with the goal of controlling the brain and manipulating its’ hosts body sounds like something you might see in a horror movie or video game. Well, that’s because it is. In the planet of The Last of Us, a cannibalistic creature infected by a fungus known as the Cordecypes has taken over the world in the 2013 Playstation-exclusive game. The post-apocalyptic game follows the journey of Joel and Ellie as they work together travelling across America in order to find a possible cure to fight a modern fungal plague that has nearly decimated the entire human race.

But the thing is this fungus doesn’t only exist in the game, it is a real thing, only that it doesn’t attack humans but rather insects. In fact, in the behind the scenes of the game, director Neil Druckmann stated that his inspiration came from this video (see below) by BBC that explores the killer fungi. David Hughes, a professor of entomology and biology at Penn State’s College of Agricultural Sciences who studies cordyceps fungus, even worked with the game developers on the game to make it more life-like.

Assistant Professor of Biological Sciences Charissa de Bekker devotes her life to studying these parasite-host interactions. She specifically studies within the field of animal behaviour, analysing parasites that change behaviour in their host’s. These manipulations range from slightly alternating behaviours to full takeover of the host’s body. “Zombie ants” are a more extreme example.

Attack of the Cordecypes

The fungus that takes over the ant’s body is known as the Cordyceps genus and includes many species of fungi. It is mainly located in hot and dry climates such as Asia. But what it does is diabolical. It germinates in a living host, kills and mummifies the larva, and then grows from the body of the host. Co-evolution between the parasite and host causes an alteration of the host’s behaviour as a way to increase the parasite’s survival. In other words, the parasite takes over the ant’s mind, causing it to feed on other insects.

Photo by Nature Photographer Robin Hoskyns

Unlike the video game, cordyceps doesn’t target the host's brain to turn it into a zombie, rather it preserves the brain while wreaking havoc elsewhere.

“To better understand how such microbial parasites control animal behavior, we looked at cell-level interactions between the parasite and its carpenter-ant host at a crucial moment in the parasite’s lifecycle — when the manipulated host fixes itself permanently to vegetation by its mandibles,” — Maridel Fredericksen, former master’s degree student in entomology at Penn State.

Stages of the ‘zombie ant’

1. Infection

A foraging carpenter ant walks through an area of the tropical rain forest floor infested with microscopic spores dropped by a mature fungus. The spore excretes an enzyme that eats through the ant’s exterior shell.

2. Death Grip

After two days, the ant leaves its tree colony and climbs down to a spot where humidity and temperature are optimal for the fungus to grow. The ant crawls onto a stem or the underside of a leaf and bites into its main middle vein so it won't fall. Then it dies.

3. Fungal Growth

The fungus eats the ant’s internal organs, using its shell as a protective casing. The fungus’ main stem (the stroma) erupts from the back of the ant’s head and grows.

4. Killing Zone

The mature fungus releases spores from its stroma. The spores fall to the ground, creating a 10-square-feet “killing zone,” which will attack new ants.