Enterobius vermicularis also known as pinworm or threadworm or seatworm is a white roundworm parasite that has worldwide distribution. It affects persons of all ages and socioeconomic status. School aged and pre-school aged children are most commonly affected.
Adult female worm migrates out of the anus, usually at night, and deposits her eggs on the perianal area, the eggs are not commonly found in feces though they may occasionally found on the surface of stool specimen or on underclothing, pajamas, or sheets about 2 to 3 hours after falling asleep. Stool is not an appropriate specimen for the diagnosis of pinworm.
Itching during the night in a child’s perianal area strongly suggests pinworm infection. Diagnosis is made by identifying the worm or its eggs.
As the eggs are mostly deposited on the perianal area scotch tape preparation is used to isolate and identify the eggs of pinworm when suspected of pinworm infections. To increase the chance of finding pinworm eggs, the scotch tape preparation method should be done on three consecutive mornings.
Method for collection of cellophane (scotch) tape preparation for pinworm diagnosis
- Take a piece of clear (not frosted) cellophane tape (Use clear, transparent tape ONLY. Cloudy, “magic” tape must not be used.) approximately 4 inches (10 cm) long
- Hold the tape between thumbs and forefingers with sticky side facing upward
- While the child is still asleep during morning, press the sticky side of the tape against the skin across the anal opening with even, through pressure. The eggs stick to the tape.
- Gently place the sticky side of the tape down against the surface of a clear glass slide.
- Label the slide in pencil with the patient name, medical record number, and date and send to parasitology laboratory
- The slide is observed under microscope to find characteristics shape of pinworm eggs
Observation under microscope:
The pinworm eggs are thick-shelled, football shaped with one slightly flattened side. Egg often contains a fully developed embryo.