The pinworm is the oldest and most widespread of the helminths. Eggs have been found in a 10,000-year-old coprolith, making this nematode the oldest demonstrated infectious agent of humans. It has been estimated to infect at least 200 million people, particularly children, worldwide, and 40 million in the United States alone. Despite evidence that its prevalence is now decreasing in the United States, in both that country and in western Eu-rope it remains the single most common cause of human helminthiasis. Infection is more common among the young and poor, but may be found in any age or economic class.
The eggs are relatively resistant to desiccation and may remain viable in linens, bed-clothes, or house dust for several days. Once infection is introduced into a household, other family members are rapidly infected.
The adult worms produce no significant intestinal pathology and do not appear to induce protective immunity.