Diagnosis can be made by examining the stools, or, occasionally by inducing the vomiting of worms. The extent of intestinal damage is then determined by the type of worm, the size of the worm, and the number of worms present. Pinworms are the most common parasitic worm in the United States. The chief symptom of this small, threadlike worm is rectal itching, especially at night. Pinworms are transmitted when eggs which lodge under the fingernails, when a person scratches, contaminate food.
Personal hygiene is most important for the control of pinworms.
Tapeworms can be contracted from eating insufficiently cooked meats, especially beef, pork and fish. The most common tapeworm in the United States is the beef tapeworm, which can grow to a length of 15 to 20 feet in the intestines. Hookworms are often found in the soil or sand in moderate climates. They can enter the body by boring holes in the skin of the bare feet, or can enter by mouth if food contaminated by dirty hands is eaten. Roundworms are most common in children.