AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

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, and 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 reinfection.

Frequency

United States

The 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 are not available, but E vermicularis infection is known to occur 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 often results from pruritus ani.

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

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Patients are often asymptomatic. Worms may be incidentally discovered when worms are found 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.

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. 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.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Inflammatory bowel disease
Dermatitis secondary to poor hygiene
Dipylidium caninum (dog tapeworm) infection

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Without a visual report, diagnosis can be confirmed using the knowledge that eggs are normally deposited in great quantities on the perineum at night.
• Wide (2 inch) transparent tape is pressed against the perineum at night or in the morning before the patient bathes to capture eggs. Three such specimens are usually consecutively collected.
• Diagnosis is made by identifying eggs under the low-power lens of microscope. Dilute sodium hydroxide or toluene should be added to the slide.

Imaging Studies

• Imaging studies are not indicated.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

• Fear, disgust, and guilt are common parental reactions to parasitic worm infestation. Many families present to the emergency department or their pediatrician with misconceptions about pinworms. In addition to prescribing medications, educating families about pinworms (see Patient Education) is helpful.
• Thorough and regular handwashing is effective in preventing disease transmission.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Mebendazole or albendazole are recommended as first-line treatment of pinworms. A second dose given 2 weeks after the initial dose helps prevent reoccurrences from reinfection.

Because asymptomatic infestation of other members in a household is frequent, simultaneously treating all household members may be reasonable. Families should be informed that repeat infestations are common. Reinfestation is treated with the same medications as the initial infestation.

Symptomatic relief of pruritus can be obtained by applying an antipruritic ointment or cream topically to the affected (usually perianal) region.

Drug Category: Anthelmintics

Parasite biochemical pathways are different from the human host, thus toxicity is directed to the parasite, egg, or larvae. Mechanism of action varies within the drug class.

Drug Name	Mebendazole (Vermox)
Description	Causes worm death by selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine where helminths dwell.
Adult Dose	100 mg PO once; repeat treatment in 2 wk
Pediatric Dose	Administer as in adults
Contraindications	Documented hypersensitivity
Interactions	Carbamazepine and phenytoin may decrease effects of mebendazole; cimetidine may increase mebendazole levels
Pregnancy	C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions	Adjust dose in hepatic impairment

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

In/Out Patient Meds

• An antihelminthic medication should be prescribed to eradicate E vermicularis.
• Application of an antipruritic ointment may help control scratching.

Deterrence/Prevention

• Thorough handwashing can deter transmission.

Complications

• Beware of skin infection from vigorous scratching to relieve pruritus.
• The association of pinworms with appendicitis, small and large intestine ulcerations, perianal abscesses, intestinal pain, transient synovitis, or enuresis is believed to be coincidental and not causal.¹

Prognosis

• Prognosis is excellent, but reinfestation is common.

Patient Education

• Inform families that dogs and cats do not harbor E vermicularis.
• Inform families that infestation may occur in spite of proper child and household hygiene.
• Counsel families to avoid overreaction through aggressive sanitary measures. Because infectious eggs may be in bedclothes and dust and remain infectious for 20 days, wet-mopping floors or vacuuming carpets and washing bedclothes are prudent precautions.
• Reassuring families that pinworms are not a sexually transmitted disease and are not evidence of child abuse may be helpful.
• Keeping the patient's fingernails trimmed to prevent excoriations is helpful.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Pinworms are rarely invasive. Attributing elevated serum immunoglobulin E (IgE) levels or eosinophilia to pinworms is unwise.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Arca MJ, Gates RL, Groner JI, Hammond S, Caniano DA. Clinical manifestations of appendiceal pinworms in children: an institutional experience and a review of the literature. Pediatr Surg Int. May 2004;20(5):372-5. [Medline].
2. American Academy of Pediatrics. Pinworm Infection (Enterobius vermicularis). Report of the committee on infectious disease. 2003;486-7.
3. Hoekelman RA. Pinworm Infestation. In: Merck Manual of Diagnosis and Therapy. 15^th ed. 1987.
4. Kucik CJ, MartinGL, Sortor BV. Common Intestinal Parasites. Am Fam Physician. Mar 2004;69(5):11621-8.
5. Lormans JA, Wesel AJ, Vanprus OF. Mebendazole in enterobiasis. A clinical trial in mental retardates. Chemotherapy. 1975;21:255.
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].
7. 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].
8. Weller TH, Sorenson CW. Enterobiasis: Its incidence and symptomatology in a group of 505 children. NEJM. 1941;224:143.

Article Last Updated: Nov 16, 2007