Cyst (left) in child's brain.
Everybody knows a few of the more overhyped parasites who infest this great rotting corpse we call Earth, but most people don't realize how many of them there are, and how resourceful they are in finding ways to get at us, their hosts. The most humiliating thing about many of them is that, though they will infect and kill us, they don't really like us. We're just sort of a rental car they want to drive to their preferred host.
Take this week's Schopenhauer Award nominee, the hydatid cyst. These cysts are one stage in the life -- cycle of Echinococcus granulosus, one of the less well -- known members of the tapeworm family. It's strange that E. granulosus hasn't gotten as much press as the better known human tapeworm, because E. Gran. is much, much more horrible. The reason for this media bias is offended human pride. You see, unlike the human tapeworm, E. Gran. doesn't value its human hosts. We're only "intermediate hosts"; what E. Gran. really wants is to find its way into the digestive system of a dog. Only in canines, its "definitive hosts," can the worm fully develop its potential.
All the worm's larvae can do while they're squirming around in your body is settle down in one or another of your internal organs, grow to the size of a basketball and kill you. From the worm's perspective, it's a waste of a good cyst. All it really hoped was that your cyst would rupture, releasing tens of thousands of "protosolices," little eggs like grains of sand, which would do their best to make their way from your corpse to a dog's intestines.
You pick up the tapeworm's eggs from dog shit. You're probably giving a big sigh of relief reading that. After all, you haven't been licking any canine asses lately. Well, let us assume you haven't.
But that doesn't mean you don't have dozens of cysts growing in your liver, brain or lungs right now. You don't need to lick a dog's ass to get the cyst. Dogs do more than enough licking of their own, and each others' asses to put billions of eggs into circulation.
All you have to do is let a dog kiss you. If you ever gave in to the impulse to let a particularly great dog lick you on the face, you could easily have swallowed an E. Gran. egg or two.
Once you've absorbed the egg, it makes its way down your digestive system to the small intestine, where it sets up housekeeping and hatches. As soon as it hatches, the larva chews its way through your intestinal wall and enters your bloodstream, floating along until it finds an internal organ that looks comfortable. Then it settles down to become a cyst. Most eggs choose the liver, but others decide to go for the brain or lungs or, in fact, any organ in the body.
Once it's picked an organ, the egg forms a wall, a cyst, around itself and begins turning out hundreds, then thousands of new eggs. As the eggs multiply, the cyst grows. If it grows large enough, it can kill you simply by squeezing the organ, as the huge cyst in the picture did to the brain of the child the cyst was using as host.
But the cyst can kill you in a much faster way. If it is ruptured -- as, for example, by a fall or a blow to the midsection -- then your cyst will burst and release tens of thousands of eggs through your bloodstream. There will be crowds of eggs colonizing every organ in your body, and you will die of the shock as thousands of tiny worms burrow through every part of your body.
And all because you let a dog lick your face. Dogs, after all, are one of the few really worthy objects of affection on this planet. Anybody who never let a dog lick their face is a jerk. And those are the people who are safe from this hideous parasite. As Scho-penhauer would be the first to point out, it's no accident that the sadistic being who created this world engineered the parasite to be passed to us that way.