A mass of decaying worms is discovered in a dance instructor's colon; a vacationer suffers headaches and a seizure; parasites get under a scientist's skin.

A parasite attacks a schoolteacher from the inside out; a dancer becomes concerned when her allergic outbreaks become lumpy and infected.

Deadly parasites attack a 9-year-old hockey player, a computer programmer and a marathon runner.

A 3-year-old girl loses a third of her body weight due to extreme bouts of vomiting and diarrhea.

A cat scratch leads to a horrifying result for a veterinary volunteer; strange liquid oozes from a college student's arm.

Stories of parasites that reside inside their traveling hosts; an Iraq war veteran pulls a foot-long worm from his body.