Pinworm

The human large intestine, including the colon and rectum; eggs are found in the perianal area and on contaminated surfaces (bedding, clothing, hands).

They feed on the content of the human large intestine, including nutrients from partially digested food.

Gravid females migrate out of the anus at night to lay thousands of eggs in the perianal folds. Movement of the worms and the glue used to attach eggs causes intense itching. Eggs are infectious within hours.

Risk: Causes enterobiasis, characterized by intense rectal itching, sleep disturbance, and irritability. While generally harmless and easy to treat with medication, they can cause secondary skin infections from scratching. Benefit: None.