Unusual endoscopic and microscopic view of Enterobius vermicularis: a case report with a review of the literature.

Abstract: Enterobius vermicularis has the broadest geographic range of any helminth and is the most common intestinal parasite seen in the primary care setting. Underappreciated is the fact that it is not always a benign disorder and could even cause life-threatening medical problems. Visualization of the actual worms during endoscopy is probably underappreciated in part because endoscopists have never actually seen the worm and or are not actively looking for, or anticipating, worms. This report describes a case of worm infection as documented during colonoscopy and confirmed by microscopy. The gross and microscopic appearance of the worm is described. Literature regarding the wide range of gastrointestinal and nongastrointestinal manifestations, including potentially life-threatening illnesses, as well as treatment options, are also reviewed.

Key Words: Enterobius vermicularis, gastrointestinal and nongastrointestinal illnesses, helminth, worms

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Enterobius vermicularis is a nematode and has the broadest geographic range of any helminth. (1) Since the first evidence of pinworm infection from Roman-occupied (30 BC to AD 395) Egypt, (2) it has been known to be the most common intestinal parasite seen in the primary care setting, regardless of race, socioeconomic status, or culture. (3) Although infection with this worm is usually thought to be asymptomatic or to cause nuisance symptoms such as perianal itching, this worm can cause severe and even life-threatening illnesses, (4-26) including fatality in primates. (27) Visualization of the actual worms during endoscopy is unusual and probably underappreciated, in part because most endoscopists have never seen these worms in real life and are not consciously looking for worms. We present a case of a worm infection as documented during colonoscopy and confirmed by microscopy.

Case Report

The patient was a 30-year-old female without a significant medical history who presented with complaints of crampy, lower abdominal pain and bloating on a daily basis. She also complained of diarrhea described as approximately 2 to 3 loose stools per day for about 1 to 2 days per month. The pain was not affected by any modifying factors including food intake, bowel movements, or increased anxiety or stress. She reported no weight loss, dysphagia, nausea, vomiting, gastrointestinal bleeding, jaundice, or constipation. Her surgical history was significant for a cesarian section. She reported no smoking, alcohol consumption, or illicit drugs. Her family history was significant for colon cancer in her grandfather and great aunt.

Physical examination revealed a fairly well-built and well-nourished female in no acute distress. She was afebrile with normal vital signs. Her abdominal examination revealed a well-healed surgical incision in her lower abdomen. Bowel sounds were normal in all four quadrants. There was mild tenderness to palpation in her bilateral lower quadrants, but no organomegaly or any masses were appreciated. The laboratory data, including complete blood count, basic chemistry profile, and coagulation studies, were within normal limits.

She underwent a colonoscopy for her symptoms of abdominal pain and intermittent diarrhea, in addition to her family history of colon cancer. There was an approximately 4-mm pinworm seen moving in the rectosigmoid area (Fig. 1). The worm was removed with biopsy forceps. Colorectal mucosa throughout was normal, both endoscopically and histologically. Histopathology of the worm confirmed it to be an E. vermicularis female with multiple eggs (Fig. 2).

Discussion

Prevalence of E. vermicularis infection in the United States is estimated to be approximately 20 to 40 million. (3) Although generally believed to be a disease of children, our case illustrates that it may occur in adults. Humans have traditionally been thought to be the only known host for pinworm; however, it has been documented in cockroaches, which has significant implications for public health. (28) Primates, especially those in captivity, may be alternate hosts. (27)

Worm

The adult worms are small. The females are larger than the males and typically range from 8 to 13 mm. The males range from 2 to 5 mm. They live mainly in the cecum and have been seen in the appendix. The gravid female worms migrate down the colon to the perianal region to deposit their eggs at night. They lay approximately 15,000 eggs at a time. The eggs are then spread by the fecal-oral route to both the original host and new hosts. Once the eggs are ingested, they hatch in the duodenum and the larvae mature as they migrate to the colon over a few weeks.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Clinical features

Most cases of E. vermicularis are asymptomatic. The main symptom is perianal itching. Symptoms can be due to mechanical stimulation and irritation, allergic manifestations, or transportation of the parasites to sites where they become pathogenic. (3) The incidence of infection in appendices by histology is as high as 2.39% in developing countries (29): no comparative data for the United States are available. In addition to causing appendicitis, (4-7) these parasites have also been implicated in other gastrointestinal problems including intestinal obstruction, (10) intestinal perforation, (16) enterocolitis mimicking Crohn disease, (8) and eosinophilic ileocolitis. (14,15)

We have previously seen a patient who was found to have a pinworm during colonoscopy and was cured of her chronic "irritable bowel syndrome" symptoms after mebendazole therapy. Hepatic involvement may also occur. (9,19) Nongastrointestinal manifestations of E. vermicularis include pruritus vulvae, urinary tract infections, postmenopausal bleeding, (13) epididymitis, (17) pelvic mass, (22) chronic sialoadenitis, (23) and unilateral salpingitis. (25,26)

Diagnosis

The diagnosis is generally made by the "Scotch tape" or "cellophane tape" test. In this test, the sticky side of the tape is pressed against the patient's perianal area and then removed. The eggs (if present) are then placed directly on a slide and viewed under a microscope. The eggs are flattened asymmetrically on one side. This test should be done first thing in the morning, before a shower or bath. The sensitivity of the test done on three consecutive mornings is 90%. (30)

Treatment

Mebendazole should be given as a 100-mg, single dose by mouth on day 1. Because reinfection is common, the dose should be repeated in 14 days. Another option is a single, 100-mg dose of albendazole if the patient is younger than 2 years old or a single, 400-mg dose if older. This dose may be repeated in 2 weeks, as in the case of mebendazole.

Pyrantel pamoate is one of the therapies uncommonly used (11 mg/kg, maximum 1 g), However, it causes significant side effects including gastrointestinal distress, neurotoxicity, and transient increases in liver enzymes. Since mebendazole and albendazole are not recommended during pregnancy, particularly in the first trimester, pyrantel pamoate should be used for symptomatic pinworm infections in pregnant women.

Because E. vermicularis is easily spread throughout households, the entire family of the patient should be treated. All bedding and clothing should be thoroughly washed. Measures to prevent reinfection and spread include clipping fingernails, frequent hand washing, and bathing.

References

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19. Baker RW, Peppercorn MA. Enteric diseases of homosexual men. Pharmacotherapy 1982;2:32-42.

20. Liu LX, Chi J, Upton MP, et al. Eosinophilic colitis associated with larvae of the pinworm Enterobius vermicularis. Lancet 1995;346:410-412.

21. de Jong MD, Baan J, Lommerse E, et al. [Severe diarrhea and eosinophilic colitis attributed to pinworms (Enterobius vermicularis)]. Ned Tijdschr Geneeskd 2003;147:813-815.

22. Sizer AR, Nirmal DM, Shannon J, et al. A pelvic mass due to infestation of the fallopian tube with Enterobius vermicularis. J Obstet Gynecol 2004;24:462-463.

23. Gargano R, Di Legami R, Maresi E, et al. Chronic sialoadenitis caused by Enterobius vermicularis: a case report. Acta Otorhinolaryngol Ital 2003;23:319-321.

24. Erhan Y, Zekioglu O, Ozdemir N, et al. Unilateral salpingitis due to Enterobius vermicularis. Int J Gynecol Pathol 2000;19:188-189.

25. Guiot F, Charlier P, Dessaive R, et al. A case of Enterobius vermicularis salpingitis. J Gynecol Obstet Biol Reprod (Paris) 1998;27:822-824.

26. Murata K, Hasegawa H, Nakano T, et al. Fatal infection with human pinworm, Enterobius vermicularis, in a captive chimpanzee. J Med Primatol 2002;31:104-108.

27. Chan OT, Lee EK, Hardman JM, et al. The cockroach as a host for Trichinella and Enterobius vermicularis: implications for public health. Hawaii Med J 2004;63:74-77.

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29. Cho SY, Kang SY. Significance of Scotch-tape anal swab technique in diagnosis of Enterobius vermicularis infection. Kisaengchunghak Chapchi 1975;13:102-114.

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Michelle Petro, MD, Kalyana Iavu, MD, and Anil Minocha, MD

From the Division of Digestive Diseases, University of Mississippi Medical Center, Jackson, MS.

Reprint requests to Dr. Anil Minocha, Division of Digestive Diseases, University of Mississippi Medical Center, Jackson, MS 39216. Email: [e-mail]

Accepted January 20, 2005.

RELATED ARTICLE: Key Points

* Although Enterobius vermicularis is usually a benign condition, it has the potential to cause life-threatening medical diseases.

* In addition to perianal itching, E. vermicularis may cause appendicitis, intestinal obstruction, intestinal perforation, enterocolitis, hepatic infection, urinary tract infections, epididymitis, sialoadenitis, and salpingitis.

* Testing involves the "Scotch tape test" on three consecutive mornings for maximal sensitivity.

* Both the patient and the family members should be treated, as E. vermicularis is easily spread throughout households.