Background
Cellulose Tape Preparations or adhesive cellophane tape is the most widely used diagnostic method for the diagnosis of pin worm diagnosis. Many commercial collection procedures are also available. Specimens should be collected in the morning before the patient bathes or goes to the bathroom. At least four to six consecutive negative slides must be examined before the patient is considered free of infection. Occasionally adult female pin worms are seen on the tapes or swabs.
Enterobius vermicularis, (Pin worm)
This is also known as the pinworm or seatworm, it is a roundworm parasite that has worldwide distribution and is commonly found in children. The adult female worm travels out of the anus, usually at night, and deposit her eggs on the perianal area. The adult female (8 to 13 mm long) is occasionally found on the surface of a stool specimen or on the perianal skin. Since the eggs are usually deposited around the anus, they are undetectable in feces and must be detected by other diagnostic techniques.
Diagnosis of pin worm infection is usually based on the recovery of typical eggs, which are described as thick-shelled, football-shaped eggs with one slightly flattened side. Each egg often contains a fully developed embryo and will be infective within a few hours after being deposited.
The most striking symptom of this infection is pruritus, which is caused by the migration of the female worms from the anus onto the perianal skin before
egg deposition.
The sometimes intense itching results in scratching and occasional scarification. In most infected people, this may be the only symptom, and many individuals remain asymptomatic. Eosinophilia may or may not be present on a CBC.
Infections tend to be more common in children and occur more often in females than in males. In heavily infected females, there may be a mucoid vaginal discharge, with subsequent migration of the worms into the vagina, uterus, Fallopian tubes, appendix, or other body sites including the urinary tract, where they become encapsulated. Although tissue invasion has been attributed to the pinworm, these cases are not numerous.
Symptoms attributed to the pinworm infection
particularly in children, include:
- nervousness,
- insomnia,
- nightmares,
- convulsions.
- In some cases, perianal granulomas may result.
In one case study, a gentleman man presented with severe abdominal pain and hemorrhagic colitis, eosinophilic inflammation of the ileum and colon, and numerous unidentifiable larval nematodes in the stool. Using morphologic characteristics and molecular cloning of nematode rRNA genes, the parasites were identified as larvae of E. vermicularis; these larvae are rarely seen and are not thought to cause disease. The authors stated that occult enterobiasis is widely prevalent and may be a cause of unexplained eosinophilic enterocolitis
Specimen collection for Cellulose Tape Preparation
The specimen is obtained from the skin of the perianal area early in the morning, before the patient has bathed or used the toilet. Preparations should be taken for at least 4-6 consecutive days with negative results before a patient is considered free of the infection.
Follow the established precautions against microbiological hazards throughout this method.
It must be assumed that all specimens collected might have infectious organisms; therefore, all specimens should be handled with the necessary precautions in mind.
Note: Specimens should be obtained before treatment therapy has begun. If therapy was initiated prior to collection of the specimen, this must be noted on the requisition.
Principle:
The Cellulose Tape Preparation is the best procedure for the demonstration of human pinworm infections. Adult Enterobius vermicularis worms inhabit the large intestine and rectum but the eggs are not usually found in fecal material. The adult female migrates out the anal opening and deposits the eggs on the perianal skin, usually during the night. The eggs, and occasionally the adult female worms, stick to the sticky surface of the cellulose tape.
Procedure
- Put a strip of cellulose tape on a microscope slide, starting 1/2 in. (1 in. = 2.54 cm) from one end and running toward the same end, continuing around this end lengthwise;
- Tear off the strip flush with the other end of the slide.
- Place a strip of paper, a
- half by 1 in between the slide and the tape at the end where the tape is torn flush.
- To obtain the sample from the perianal area, peel back the tape by gripping the label, and with the tape looped (adhesive side outward) over a wooden tongue depressor held against the slide and extended about 1 in. beyond it,
- Press the tape firmly against the right and left perianal folds.
- Spread the tape back on the slide, adhesive side down.
- Write the name and date on the label.
Transport:
Sample should be transported within 2-8° C within 72 hours.
Cellulose Tape Preparation examination procedure
- Lift one side of the tape, apply 1 small drop of toluene or xylene, and press the tape down on the glass slide.
- The preparation will then be cleared, and the eggs will be visible.
- Examine the slide with low power and low illumination.
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