Pinworm infection is caused by a small, thin, white roundworm called Enterobius vermicularis. Although pinworom infection can affect all people, it most commonly occurs among children, institutionalized persons, and household members of persons with pinworm infection. Pinworm infection is treatable with over-the-counter or prescription medication, but reinfection, which occurs easily, should be prevented.

Image: Left: Adult male of E. vermicularis from a formalin-ethyl acetate (FEA) concentrated stool smear. The worm measured 1.4 mm in length. Image courtesy of Centre for Tropical Medicine and Imported Infectious Diseases. Right: Image of the eggs of the human parasite Enterobius vermicularis, or "human pinworm, " captured on cellulose tape under significant magnification. Credit: DPDx, PHIL.