has been attributed to the pinworm, these cases are not numerous. Symptoms that have been attributed to the pinworm infection, particularly in children, include nervousness, insomnia, nightmares, and even convulsions. In some cases, perianal granulomas may result (3).
In one report, a homosexual 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 (9).
The most widely used diagnostic procedure for pinworm infection is the cellulose tape (adhesive cellophane tape) method (5, 10–14) (Fig. 5.1 to 5.3). Several commercial collection procedures are also available. Specimens should be obtained in the morning before the patient bathes or goes to the bathroom. At least four to six consecutive negative slides should be observed before the patient is considered free of infection. Occasionally adult female pinworms are seen on the tapes or swabs.
Figure 5.1 Collection of Enterobius vermicularis eggs by the cellulose tape method. (Illustration by Sharon Belkin.) doi:10.1128/9781555819002.ch5.f1
Figure 5.2 Diagram of a commercial kit (Evergreen Scientific) for use in sampling the perianal area for the presence of pinworm (E. vermicularis) eggs. On the left is the vial containing the sampler, which has sticky tape around the end. Once this is applied to the perianal area and eggs are picked up on the tape, the label area is placed at one end of the slide. The sticky tape is rolled down the slide and attaches to the glass. This device is easy to use and provides an area sufficient for adequate sampling. A minimum of four to six consecutive negative tapes are required to rule out a pinworm infection; most laboratories are accepting four rather than requesting the full six. (Illustration by Sharon Belkin.) doi:10.1128/9781555819002.ch5.f2
Figure 5.3 (Top) Enterobius vermicularis (pinworm) eggs seen in a Scotch tape preparation; note the football-shaped eggs with one side a bit flatter than the other. In some preparations, eggs are seen that contain fully developed larvae; such eggs are infective. (Middle) Adult female pinworm found on a collection device. Note the large, round esophageal bulb. (Bottom) Adult female pinworm, enlarged anterior end. Note the cephalic expansions around the end of the head, as well as the large, round esophageal bulb. doi:10.1128/9781555819002.ch5.f3
Collection of the Specimen
1. Place 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, 1/2 by 1 in., between the slide and the tape at the end where the tape is torn flush.
2. 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.
3. Spread the tape back on the slide, adhesive side down.
4. Write the name and date on the label.
Note Do not use Magic transparent tape; use regular clear cellulose tape. If Magic tape is submitted, a drop of immersion oil can be placed on top of the tape to facilitate clearing.
Examination
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.
The anal swab technique (15) is also available for the detection of pinworm infections; however, most laboratories use the cellulose tape method because it eliminates the necessity for preparing and storing swabs. At least four to six consecutive negative swabs should be obtained before the patient is considered free of infection.
Collection of the Specimen
Specimens should be obtained in the morning before the patient bathes or goes to the bathroom.
1. Prepare a mixture of 4 parts petrolatum to 1 part paraffin, and heat until liquid (just melted).
2. Dip the end of the cotton swab into the mixture, remove the swab, and allow it to cool. If the cotton is not thoroughly coated, dip it again.
3. Store the coated swab in a 100- by 13-mm tube, and plug the end of the tube with cotton. These tubes may be stored for long periods, preferably under refrigeration.
4. Rub the swab gently over the perianal surface and into the folds. Insert the swab into the anal opening about 1/4 in. and then replace it in the tube.
Examination
1. Fill the tube containing the swab half full of xylene or xylene substitute, and let it stand for 3 to 5 min.
2. Remove the swab, and centrifuge the tube at 500 × g for 1 min.
3. Remove the supernatant fluid with a pipette (do not pour it off).
4. Place the sediment on a slide, and examine the material for eggs. The fluid can be examined under a coverslip, in a depression slide, or in a wax pencil circle drawn on the slide (to prevent the fluid from spreading).
Material obtained from sigmoidoscopy can be helpful in the diagnosis of amebiasis that has not been detected by routine fecal examinations; however, a series of at least three routine stool examinations for parasites should be performed on each patient before sigmoidoscopy examination is done. Another option would be to use the immunoassay kits that are designed to detect either the Entamoeba histolytica/E. dispar group/complex or specifically pathogenic E. histolytica; fresh or frozen stools are required for these kits.
Material from the mucosal surface should be aspirated or scraped and should not be obtained with cotton-tipped swabs. If swabs are the only method available, a small amount of cotton should be used on the end of the stick and should be wound tightly to prevent absorption of the sigmoidoscopy material into the cotton. At least six representative areas of the mucosa should be sampled and examined (six samples, six slides) (
