[A] major difficulty in the parasites life is the return to water. It — Parasitism

"It is about the most awful thing you can imagine in terms of a non-fatal ailment. Its a parasitic disease and you know youve got it when at some point you develop a blister on your skin on your leg or your arm, and its a burning blister and soon what emerges is a worm, and its a worm that eventually, as it comes out, could be three-feet-long. It looks like a long strand of angel hair pasta and its excruciatingly painful as it comes out. And the way its transmitted is through drinking water. The worm, when it comes out, youve got that burning blister, your instinct is to want to immerse the skin in water. Well, when you do that, the worm puts out thousands and thousands of larvae that infects the drinking water. If anyone drinks the water, it gets into their system and a year later they develop a blister and out comes another worm."

"Fell Oestrus buries in her rapid course Her countless brood in stag, or bull, or horse; Whose hungry larva eats its living way, Hatchd by the warmth, and issues into day."

"The wingd Ichneumon for her embryon young Gores with sharp horn the caterpillar throng. The cruel larva mines its silky course, And tears the vitals of its fostering nurse."

"In this strange and apparently cruel operation one circumstance is truly remarkable. The larva of the Ichneumon, though every day, perhaps for months, it gnaws the inside of the caterpillar, and though at last it has devoured almost every part of it except the skin and intestines, carefully all this time it avoids injuring the vital organs, as if aware that its own existence depends on that of the insect upon which it preys!"

"Nowhere is it more true that "prevention is better than cure," than in the case of Parasitic Diseases."

"The insidious lethality of a parasitic wasp, the cruelty of a cat playing with a mouse – these are, after all, just the tip of the iceberg. To ponder natural selection is to be staggered by the amount of suffering and death that can be the price for a single, slight advance in organic design. And it is to realize, moreover, that the purpose of this "advance" – longer, sharper canine teeth in male chimpanzees, say – is often to make other animals suffer or die more surely. Organic design thrives on pain, and pain thrives on organic design."