Critical Intel

Critical Intel
Mind-Controlling Parasites and The Last of Us

Robert Rath | 14 Aug 2013 12:00
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Cordyceps Ant

This form of behavior manipulation is clearly present in The Last of Us. You may have noticed, for example, that the infected tend to congregate inside buildings and underground, preferring damp, enclosed spaces. Not only does this seem to be ideal conditions for the fungus to fruit and release spores - you always find the worst nests inside hallways and closets - but it also concentrates the spore density, increasing the chance of transmission to a new host. Likewise, the fictional Cordyceps seems to compel some of the early-stage infected known as "Runners" and "Stalkers" to seek out and attack humans, spreading the infection through tainted saliva. This too, has precedent in nature - the rabies virus infects the host's brain, making it unusually aggressive and more likely to attack and bite another animal, transmitting the virus. Violent outbursts are known to occur in humans as well. One rabies patient in Manila recently went on a rampage, attacking people, beating them with wood and causing enormous property damage before he was restrained - which sounds fairly similar to the Runner's fist-pounding rage.

Clickers and Bloaters, on the other hand, seem to play a different role in host manipulation than the more aggressive and situationally-aware early-stage infected. Advanced-stage infected seem primarily defensive in nature, patrolling the areas where the Cordyceps breeds, keeping the fungus safe from any external threats that may kill it before it has a chance to fruit and release spores. Advanced-stage infected don't actively seek out new hosts and aren't generally aggressive unless a threat comes into their immediate area - Clickers leave well enough alone unless they blunder into a survivor or hear a threatening noise, and Bloaters only emerge from extremely advanced (and vulnerable) pockets of fungus when intruders threaten the health of a large colony. In both these cases, Clickers and Bloaters use their host body to defend the fungus in the hopes that it will survive to maturation.

This behavior, known as "bodyguard manipulation," is the modus operandi of several species of parasitic wasps, which lay their eggs in caterpillars then manipulate the compel the dying host to defend their young. When the pupating parasitoids have eaten their fill from the caterpillar's still-living organs, they exit the body and form a cocoon mass. The fatally wounded caterpillar then coils his body on top of the cocoon and lashes its head around, defending the pupae from any predators that come near. It's a terrifying thought - an animal that can get into your brain, nudging and rearranging, playing your nervous system so that you're acting in its best interest without you ever knowing. It's a nightmare scenario straight out of Invasion of the Body-Snatchers, but thankfully, parasites that control human behavior exist solidly in the realm of science fiction, right?

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