Ascariasis (Round Worm Infection)
Ascariasis is the illness arising from infection with Ascaris lubricoides, the intestinal roundworm, the most common worm infection in humans. Ascaris eggs are found in the soil. Infection occurs when a person swallows infective ascaris eggs. Once in the stomach, larvae (immature worms) hatch from the eggs, penetrate the intestinal wall and are carried to the lungs then where they leave the circulation and enter the air passages passing upward to the throat where they are then swallowed. Once swallowed, they reach the intestines and develop into adult worms. Adult female worms can grow over 12 inches (4.8 cm) in length. Adult male worms are smaller. Adult female worms lay eggs that are then passed in feces; this cycle takes between 2 and 3 months. Adult worms can live 1 to 2 years. Infection occurs worldwide. It is most common in tropical and subtropical areas where sanitation and hygiene are poor. Children are infected more often than adults. In the US, infection is not common and occurs mostly in rural areas of the southeast. Pigs can be infected with ascaris. Occasionally, a pig infection can be spread to humans.