Phalenar: "We Are The Zombies": We Are The Zombies Hydrophobia, or fear of water, is a classic symptom of rabies infection. So is aerophobia (fear of moving air) and, as the disease progresses, an uncontrollable urge to bite. These seemingly random behaviors stem from changes the virus causes in the central nervous system of its host. And they may have a fortuitous side effect for the virus itself. The actions may actually help it transmit itself into a new victim. Because the rabies virus is spread through saliva, causing an urge to bite, for example, would be a useful microbial “strategy.” So far, however, infectious disease veterinarians haven’t found adaptive purposes for causing a fear of water or moving air. Or consider Enterobius vermicularis, a.k.a. pinworms. This common childhood infection alters human behavior by drawing hands away from more productive activities, like homework and setting the table, and redirects them into ferocious anal scratching. This scratching serves two purposes for E. vermicularis: It helps burst the gravid females’ bodies, releasing the ten thousand eggs they each carry. And it helps those freshly exposed eggs burrow under the child’s fingernails, where they wait patiently for the next thumb suck or nail bite to permit them entry into the host’s mouth and, from there, his GI tract, where they reproduce. Or take Toxoplasma gondii. Infection with this protozoan has an unusual effect on rodents: it makes them lose their fear of cats. From the rodent’s perspective, of course, this is terrible. It makes them easy prey. But from the toxo’s point of view, it could not be more clever. That’s because the only place on Earth that Toxoplasma gondii can reproduce is inside a cat’s intestine. By making rodents fearless, the parasite practically gift-wraps and delivers itself to the cats’ claws...

We Are The Zombies

Hydrophobia, or fear of water, is a classic symptom of rabies infection. So is aerophobia (fear of moving air) and, as the disease progresses, an uncontrollable urge to bite. These seemingly random behaviors stem from changes the virus causes in the central nervous system of its host. And they may have a fortuitous side effect for the virus itself. The actions may actually help it transmit itself into a new victim. Because the rabies virus is spread through saliva, causing an urge to bite, for example, would be a useful microbial “strategy.” So far, however, infectious disease veterinarians haven’t found adaptive purposes for causing a fear of water or moving air. Or consider Enterobius vermicularis, a.k.a. pinworms. This common childhood infection alters human behavior by drawing hands away from more productive activities, like homework and setting the table, and redirects them into ferocious anal scratching. This scratching serves two purposes for E. vermicularis: It helps burst the gravid females’ bodies, releasing the ten thousand eggs they each carry. And it helps those freshly exposed eggs burrow under the child’s fingernails, where they wait patiently for the next thumb suck or nail bite to permit them entry into the host’s mouth and, from there, his GI tract, where they reproduce. Or take Toxoplasma gondii. Infection with this protozoan has an unusual effect on rodents: it makes them lose their fear of cats. From the rodent’s perspective, of course, this is terrible. It makes them easy prey. But from the toxo’s point of view, it could not be more clever. That’s because the only place on Earth that Toxoplasma gondii can reproduce is inside a cat’s intestine. By making rodents fearless, the parasite practically gift-wraps and delivers itself to the cats’ claws and jaws … and from there to guaranteed reproduction. Humans are “dead-end” hosts for toxo, meaning it can’t reproduce in us. But the parasites can still enter our bodies when we eat or touch infected meat, soil, or cat feces. Once inside our brains, the toxo can “encyst,” essentially lying dormant and waiting to get back into a cat. The pathogen doesn’t know whether it’s in a mouse or a mail carrier, a rat or a receptionist. But it continues to produce chemicals and help itself to nutrients in our blood and tissues. In fact, many of us have these encysted toxo infections. And, incredibly, this microorganism may affect our behavior as individuals. Exposure to toxo in the womb may be a contributing factor in developing the often devastating human disease of schizophrenia.

Zoobiquity Barbara Natterson-Horowitz

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