Introduction
Background
Enterobius vermicularis, a small nematode, is a common cause of helminthic infestation in the United States. The female nematode averages 10 mm X 0.7 mm, whereas males are smaller. All socioeconomic levels are affected. Infestation often occurs in family clusters. Infestation does not equate with poor home sanitary measures (an important point when discussing therapy).
Pathophysiology
E vermicularis is an obligate parasite; humans are the only natural host. Fecal-oral contamination via fomites (toys, clothes) is a common method of infestation. After ingestion, eggs usually hatch in the duodenum within 6 hours. Worms mature in as little as 2 weeks and have a life span of approximately 2 months.
Adult worms normally inhabit the terminal ileum, cecum, vermiform appendix, and proximal ascending colon. The worms live free in the intestinal lumen, and little evidence supports invasion of healthy tissue under normal conditions. The female worm migrates to the rectum after copulation and, if not expelled during defecation, migrates to the perineum (often at night), where an average of 11,000 eggs are released. Eggs become infectious within 6-8 hours and, under optimum conditions, remain infectious in the environment for as long as 3 weeks.
Because of the short incubation time until the ova are infectious, eggs that are deposited under the fingernails during scratching and then placed in the mouth may be a mode of reinfestation.
Frequency
United States
Prevalence is approximately 5-15% in the general population; however, this rate has declined in recent years. Prevalence rates are probably higher in institutionalized individuals. Humans are the only known host.
International
Prevalence data vary by country. E vermicularis infestation occurs worldwide.
Mortality/Morbidity
Secondary bacterial skin infection may develop from vigorous scratching to relieve pruritus. Reinfestation is common. Infection can develop as long as female pinworms continue to lay eggs on the skin. Restless sleeping may be due to pruritus ani. Infestation has been reported to cause enuresis.
Race
All races are subject to infestation.
Sex
Infestation can occur in males and females.
Age
The prevalence is greatest in children aged 5-9 years, but all ages can be affected.
Clinical
History
- Patients with enterobiasis are often asymptomatic. Worms may be incidentally discovered when they are seen in the perineal region.
- If patients are symptomatic, pruritus ani and pruritus vulvae are common presenting symptoms. However, one study failed to find an increase of these symptoms in infested children compared with matched control subjects.
- Restlessness during sleep is noted by the parents of many patients.
- Enuresis may be a symptom in children with pinworms.
Physical
- Patients often have excoriation or erythema of the perineum, vulvae, or both, but infestation can occur without these signs.
- Visual sighting of a worm by a reliable source (eg, a parent) is usually accepted as evidence of infestation and grounds for treatment.
- Worms can be found in stools or on the patient's perineum before bathing in the morning.
- Occasionally, the gravid female worm may aberrantly migrate into the female genitalia and produce vaginitis.1 Incidental recovery at necropsy or surgery of small granulomatous lesions surrounding the worm, larvae, or eggs in the salpinx and peritoneum demonstrates the worm's ability to ascend the female genital tract.
Causes
- Enterobiasis is caused by the nematode E vermicularis.
More on Enterobiasis |
 Overview: Enterobiasis |
| Differential Diagnoses & Workup: Enterobiasis |
| Treatment & Medication: Enterobiasis |
| Follow-up: Enterobiasis |
| Multimedia: Enterobiasis |
| References |
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References
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Samkari A, Kiska DL, Riddell SW, et al. Dipylidium caninum mimicking recurrent enterobius vermicularis (pinworm) infection. Clin Pediatr (Phila). May 2008;47(4):397-9. [Medline].
American Academy of Pediatrics. Pinworm Infection (Enterobius vermicularis). Report of the committee on infectious disease. 2009;519-20.
Hoekelman RA. Pinworm Infestation. In: Merck Manual of Diagnosis and Therapy. 15th ed. 1987.
Kucik CJ, MartinGL, Sortor BV. Common Intestinal Parasites. Am Fam Physician. Mar 2004;69(5):11621-8.
Lormans JA, Wesel AJ, Vanprus OF. Mebendazole in enterobiasis. A clinical trial in mental retardates. Chemotherapy. 1975;21:255.
Otu-Bassey IB, Ejezie GC, Epoke J, Useh. Enterobiasis and its relationship with anal itching and enuresis among school-age children in Calabar, Nigeria. Ann Trop Med Parasitol. Sep 2005;99(6):611-6.
Song HJ, Cho CH, Kim JS, et al. Prevalence and risk factors for enterobiasis among preschool children in a metropolitan city in Korea. Parasitol Res. Sep 2003;91(1):46-50. [Medline].
Symmers WS. Pathology of oxyuriasis; with special reference to granulomas due to the presence of Oxyuris vermicularis (Enterobius vermicularis) and its ova in the tissues. AMA Arch Pathol. Oct 1950;50(4):475-516. [Medline].
Weller TH, Sorenson CW. Enterobiasis: Its incidence and symptomatology in a group of 505 children. NEJM. 1941;224:143.
Further Reading
Keywords
enterobiasis, pinworms, oxyuriasis, human pinworm, pinworm infection, pruritus ani, pruritus vulvae, vaginitis, enuresis, treatment, diagnosis
