Parasites are creatures that exploit another creature — the host — for food, shelter or protection. Sometimes parasites are fairly innocuous. For example, you probably have some intestinal protozoa flailing around in your guts right now that are feeding off of your breakfast, but those little guys most likely aren't going to make you sick.
Then there's the Loa loa worm, which is native to wet areas of West Africa. Spread by fly bites, the worm courses beneath your skin and can wiggle its way into your eyes. If your friends peer closely enough they'll actually be able to see your little parasite writhing around, and you'll be able to feel it, too. Horrifying? Yes. But the Loa loa isn't alone.
All told, there may be around 100 or so parasites built specifically to latch onto humans. That doesn't really capture the whole story, though. Some researchers estimate that most creatures on Earth probably exhibit parasitic behavior at some point in their lifecycles, and that this kind of activity is actually necessary to keep ecosystems working properly. Dog eat dog world, indeed.
If parasitism is an integral part of life on Earth, what exactly does that say about our lives on this planet? Earth may be our life raft in an ocean of universal vastness and uncertainty, but it is far from a benign and friendly place. From volcanoes to venomous snakes to jarring earthquakes, our home world is a place loaded with danger in every nook and cranny. Be safe out there — our Earth is trying to kill you.