When the poet Walt Whitman wrote "I contain multitudes," he probably wasn't thinking about intestinal worms. However, if you are infected with Ascaris lumbricoides, you might find this verse particularly appropriate. Your intestines may be packed with animals resembling large white night-crawlers from a fisherman's bait bucket -- each sharing the delicious meal you ate last night and laying up to 200,000 eggs per year. Although some patients can have stomach cramps or even bowel obstruction, your first symptom might be be a six-worm wiggling out of your nose and jumping into your bowl of corn flakes during breakfast.
The life cycle starts when you (accidentally!) swallow a worm egg that hatches in your digestive tract. The larva burrows into your intestinal wall, and then enters a blood vessel that eventually delivers the larva to your lungs. The worms then crawl up your airways until they are coughed up and swallowed again to return to the same location they started -- your intestinal tract. But now the worms have become adults, and will pass their eggs through your stools and into your organic natural compost pile, where they can survive for years, until they make their way into your neighbors' mouths via home-grown strawberries.
Don't worry -- in spite of their revolting life style, the worms are seldom fatal and are easily treated. A couple of doses of mebendazole and you'll be pooping out dead worms for a week.