Cat-Loving Rats and The End of Humanity As We Know It

So, you think surviving the zombie apocalypse is something that you will never have to do?  Really?  Well, have a read of this educational essay from Justin over at Swishfish and think again, my friends....

Zombies are just a myth, right? They are an interesting literary and filmic diversion that play upon our fear of things that move in the night, aren't they? “28 Days Later” is freaky but that is not actually going to happen, is it? The zombie apocalypse couldn't actually happen....could it?

To be honest, there is pretty much no chance of us having to refer to our zombie contingency plan; Will Smith and Charlton Heston are unlikely to become legends of zombie/vampire fighting, anyway: this isn't Oscar week. Sure, there are chemicals that change behaviour through nefarious (the US government's MKULTRA) or natural (for example ergotism from infected crops) means, but these do not lead to the pandemic of foaming-mouthed brain-eaters of zombie lore, do they? We need something like a parasite or virus that will infect us en masse. Take a look at the animal kingdom and there are a few great examples of what we might call real zombies.

Ants are the kings of the animal zombie world, with two widespread and well-documented examples. Firstly, the parasite Dicrocoelium dendriticum has a fascinating life cycle: it is excreted from a cow, where snails eat its eggs, which grow into baby flukes in their respiratory system and are (I kid you not) coughed out when they get irritating. Here's where the zombieism comes in. If you're an ant (which I am not for one second suggesting you are) then snail mucous is an irresistible treat; this particular delight is, however, laced with baby parasites. The baddies are eaten by the ant, grow, and some of them take over the ant's nerve centre. Here they wait until the ant is going home for the evening, and force them to wander off and attach themselves to a blade of grass, where they can be eaten by a cow. Excrete and repeat.

The second example is less dramatic but has been around for a long time, with evidence showing that the fungus Ophiocordyceps unilateralis has been possessing ants for around 50 million years. Once it has infected them, it compels them to climb to a leaf at just the right place in terms of heat, humidity, and location; they then attach themselves to the leaf in a “death grip”. The fungus busts out of the zombie's head and spreads its spores.

There are other examples, primarily in insects, including:

• The hairworm, which lives inside grasshoppers and produces chemicals that make them commit suicide by jumping into bodies of water, where the parasites can enter the next stage of their life cycle.
• The green-banded broodsac, a worm that infects snails by living in their tentacles and reducing their light sensitivity, making the snails more likely to be eaten by birds. Birds are, of course, the host for the next stage of the worm's life.
• The emerald cockroach wasp, which turns cockroaches into zombies by stinging specific parts of their “brains” and altering their behaviour. These “mind-controlled” roaches are then led to the wasp's lair and implanted with eggs.
• The parasitic wasp Glyptapanteles, which takes over the body of a specific type of moth caterpillar and, whilst growing inside, change the host's behaviour so that it attacks predators (sound like a zombie to you?)
• Mammals are not immune, by the way. Toxoplasma gondii infects rats and transforms cat aversion into cat attraction so that it can be brought into contact with its ultimate host. That's right, a parasite that stops rats being afraid of cats.

In reality, all these zombie animals are just really cool examples of symbiosis and how evolution can throw up extraordinarily complex and ingenius solutions to life's little reproductive problems. The chances of something like that happening to humans are nearly impossible. It's that “nearly” that is the tantalising part to those dealing in horror and science fiction...

There are, of course, other ways in which the zombie apocalypse might come, which are probably much more likely. What if an existing virus (say Ebola) changed, either on its own or with the helping hand of a super-villain, so that it attacked the brain and altered behaviour? “28 Days Later” and its sequel revolved around a virus that was basically rabies: how about mutating that and bio-bombing our enemies into bloodthirsty doom?

Probably not. But I don't want to spoil Zombie Week by saying it can't happen, and at least you have read some interesting cases of mind-controlled animals that sound like fiction but aren't. You can sleep easy tonight. Unless, that is, you read up more on toxoplasmosis, the rat killer mentioned earlier. The fascinating thing here is that estimates suggest up to a third of humans are infected with the parasite, with rarely any evidence of symptoms. Recent studies have, however, linked the infection with changes in human behaviour: higher rates of disorders including depression, anxiety, and schizophrenia are being associated with T. gondii. Comparing infected and uninfected humans via personality tests has revealed differences in those who are infected. In other words, there is already a parasite that has infected a significant proportion of the human population which has the potential to change your behaviour.

So the next time you are in a busy room, take a look around: who is so controlled by the disease that they might want to eat your brain? It could be anyone. RUN! 

Next up in Week of The Living Dead...
Now that you know what to look for, thanks to Adele, and the likelihood of finding it, thanks to Justin, it's time to look at British zombie tale, The Enemy...