After they hatch, the worms move down the length of the intestine, trying to get out to lay eggs. When the children scratch their itchy bottoms, the tiny eggs can get under their fingernails. As the children move around the house, the eggs may be spread, and other family members may become infected. Also contact with soiled underclothing, night clothing or bedding may help in spreading infection. Sometimes adults breathe in the eggs when the bed covers are shaken.
Children easily infect each other while they are playing.
Pets do not spread pinworms, although they may carry their own kinds of worms. Also the eggs deposited near the anus may hatch and the larvae may find their way back into the gut causing auto-infection. They usually cause no symptoms whatsoever. The most common symptom is itching around the anal area typically so at night when the female worms travel down to lay eggs. Restless sleep, nightmares, teeth grinding and perhaps bed-wetting may also be as a result of worm infection.