The roundworm, Ascaris lumbricoides.

Ascaris lumbricoides is a significant health problem. One billion people worldwide are infected. Most frequently it is seen in malnourished people residing in developing countries. Areas with modern water and waste treatment have a low incidence. The major serious sequelae associated with the parasite is intestinal obstruction, which occurs at a rate of 2 per 1000 people infected. Intestinal obstruction is fatal in 6 per 100,000 children. An estimated 20,000 people die of this infection annually. Although effective chemotherapy is available, long-term cure and ultimate eradication of this parasite requires improved sanitation and change in some cultural habits. The incidence in the United States has seemed to decrease, presumably because of improved sanitation. This problem is still encountered occasionally, necessitating familiarity with the clinical manifestations and treatment modalities. A professional explanation of this parasite and its life cycle will go far to eliminate the guilt of parents whose child has "passed a worm."