Chapter 24

PARASITES R US

Let us recap:

Parasites are bad.

They suck your blood out of the lining of your stomach. They grow into two-foot-long snakes and roost in the skin of your leg. They infect your cat and then jump up your nose to live in cysts inside your brain, turning you feline-centric and irresponsible. They take over your blood cells in hopes of infecting passing mosquitoes, leaving your liver and brain crumbling from lack of oxygen. They incense your immune system, causing it to destroy your eyeballs. They take terrible advantage of snails and birds and ants and monkeys and cows, stealing their bodies and their food and their evolutionary futures. They almost starved twenty million people in Africa to death.

Basically, they want to rule the world and will crumple whole species like balls of paper and then reshape them in order to carry out their plans. They turn us into walking undead, ravaged hosts that serve only their reproduction.

That's bad. But...

Parasites are also good.

They have bred howler monkeys to live in peace with one another. Their lousy genes help track the history of the human species. They prevent cows from overgrazing grasslands into windblown deserts. They tame your immune system so it doesn't destroy your own stomach lining. Then they go and save those twenty million people in Africa, by laying their eggs in those other parasites, the ones trying to starve them.

Which is all quite good, really.

So parasites are bad and good. We depend on them, like all the other checks and balances of the natural world; predators and prey, vegetarians and carnivores, parasites and hosts all need one another to survive.

Here's the thing: They're part of the system. Like government bureaucracies with all those forms that have to be filled out in triplicate, they may be a pain, but we're stuck with them. If every parasite suddenly disappeared from the earth one day, it would be a much bigger disaster than you'd think. The natural order would crumble.

In short, parasites are here to stay, which is a good thing, really. We are what we eat, and we consume them every day, the worms lodged in slices of rare beef or the toxoplasma spores floating up our noses from boxes of cat litter. And they eat us every day too, from ticks sucking our blood to microscopic invaders reshaping our cells. The exchange goes on unendingly, as certain as the earth traveling around the sun.

In a manner of speaking, parasites are us.

Deal with it.