Roundworm infections are diseases of the digestive tract and other organ systems caused by nematodes--parasitic worms with long, cylindrical bodies. Roundworm infections are widespread throughout the world, and humans acquire most types of roundworm infection from contaminated food or by touching the mouth with unwashed hands which have come into contact with the parasite larva. The severity of infection varies considerably from person to person. Children are more likely to have heavy infestations and are also more likely to suffer from malabsorption and malnutrition than adults.

The type and symptoms of roundworm infections vary according to the species of nematode which causes them. Anisakiasis infection is caused by anisakid roundworms. Humans are not the primary host for these parasites which infest whales, seals, and dolphins. However, crabs ingest roundworm eggs from the feces of these animals. In the crabs, the eggs hatch into larvae that can...