Basics
Description
- Infection by a small, white nematode (roundworm), typically Enterobius vermicularis
- Pinworms may also be caused by Enterobius gregorii in Europe, Africa, and Asia.
Epidemiology
- Considered the most common helminthic infection of humans (the only known natural host) and the most common worm infection in the United States.
- Occurs in school-aged children (5 " 10 years) and preschool children predominantly
- Does occur in adults, usually in those caring for infected children. Some individuals may be predisposed to having either heavy or light worm burdens.
- Independent of socioeconomic status
Prevalence
- U.S. infection rates: 5 " 15%
- Among children, people caring for infected children, and people who are institutionalized, prevalence can reach 50%.
- Occurs worldwide but is more prevalent in temperate climates
General Prevention
- Decontaminate the environment by washing underclothes, bedclothes, bedsheets, and towels.
- Maintain good hand hygiene, including hand washing and proper toileting.
- Keep fingernails short and avoid nail biting.
- Treat family members and close contacts.
Pathophysiology
- E. vermicularis eggs are ingested and hatch in the human 's stomach and duodenum. Then the larvae migrate to the ileum and cecum. Adult worms copulate in the cecum.
- The pregnant female pinworm migrates from the cecum to the anus ’ Ό5 weeks later and deposits eggs on the perianal skin (at which point the female pinworm usually dies). Thousands of eggs are laid, which may result in hundreds of worms.
- Pruritus is caused by the perianal deposition of eggs and a mucosal mastocytosis response. Other GI symptoms, such as anorexia or abdominal pain, may occur because of the mucosal inflammatory response.
- Granulomas may form if dead worms and eggs invoke an inflammatory response in ectopic locations such as the peritoneal cavity, vulva, cervix, uterus, and fallopian tubes.
Etiology
- Ingestion of organism via fecal " oral transmission
- Can be spread directly, hand-to-mouth, or via fomites found on toys, bedding, clothing, toilet seats, and baths
Diagnosis
History
- Prior pinworms or sibling with pinworms
- Eggs can survive for several days in the environment, and the incubation period can be 1 " 2 months.
- Spread can occur between family members.
- Daytime itching
- Pinworm infections usually cause perianal itching during the night or just before waking in the morning.
- Daytime perianal or perivulvar itching or irritation is likely due to other causes.
- Fevers, diarrhea, or vomiting
- Pinworms are highly unlikely to cause systemic symptoms (except in rare cases where they migrate aberrantly).
- Visible worms at night
- Pinworms may be seen 2 " 3 hours after the child has gone to sleep. Female worms are 8 " 13 mm, and males are 2 " 5 mm.
- They may be visible as small, white worms in the perianal area at night.
Physical Exam
- Exam may be normal, and the child may be well-appearing.
- May have self-inflicted, perianal excoriation
- Pinworms may be visible perianally.
- Infection is characterized by perianal pruritus that occurs at night or just before waking.
- Difficulty sleeping, decreased appetite, and/or abdominal pain may occur.
Diagnostic Tests & Interpretation
Lab
- Stool or urine samples for ova or parasites
- Generally not helpful or recommended
- Very few ova present in stool (even more rare in urine)
- Blood count for eosinophilia
- Generally not helpful or recommended
- Eosinophilia is not observed because usually there is no tissue invasion.
Diagnostic Procedures/Other
- Transparent tape, Scotch tape test
- In the morning, prior to the child awakening and before defecation or washing, the adhesive side of transparent tape is applied to the perianal area.
- After removal, the tape is applied to a glass slide and examined under light microscopy for pinworm ova. Several samples may be necessary to see the pinworms.
Differential Diagnosis
- Infection
- Other parasites (e.g., Strongyloides stercoralis)
- Nonparasitic vulvovaginitis (due to bacterial, fungal, or viral causes)
- Dermatologic
- Contact or irritative diaper dermatitis
- Hidradenitis suppurativa
- Irritative vulvovaginitis secondary to soaps, bubble baths, or lotions
- Anal fissures (usually cause pain rather than itching)
- Miscellaneous
- Behavioral: self-stimulation (normal)
- Sleep disorders not owing to nocturnal pruritus
- Hemorrhoids
Treatment
Medication
Single-drug and single-dose therapy with one of the following agents:
- Mebendazole, 100 mg (available as a chewable tablet) PO once, may repeat in 2 weeks if symptoms still present
- Pyrantel pamoate, 11 mg/kg (maximum 1 g) PO once, may repeat in 2 weeks
- Albendazole, 400 mg PO once, may repeat in 2 weeks
- Experience is limited in children <2 years of age. Consider risks and benefits before use.
- Caution in treating pregnant individuals with anthelminthic medications because mebendazole, pyrantel pamoate, and albendazole are all category C and are not recommended in pregnancy.
Additional Treatment
General Measures
- Reinfection is common especially if not all close contacts are treated.
- Treat all symptomatic contacts, and consider treating close household contacts, especially if repeated infections have occurred.
- Reinfection can occur if eggs remain on bed linen or clothing.
- Infection may be asymptomatic and transmitted to others.
- Autoreinfection can occur if eggs remain under the nails.
Ongoing Care
Follow-up Recommendations
Patient Monitoring
Watch for signs of reinfection.
Patient Education
- National Library of Medicine 's health information site: http://www.nlm.nih.gov/medlineplus/pinworms.html
- Centers for Disease Control and Prevention site: http://www.cdc.gov/healthywater/hygiene/disease/pinworms.html
Prognosis
- Reinfection is common.
- With appropriate treatment, symptoms resolve within a few days.
- Any chronic symptoms are likely due to recurrence rather than chronic infection because the life cycle of the adult worm is short, with eggs being laid by the adult worm within 5 weeks.
Complications
- Intestinal
- Appendicitis (uncommon)
- Bacterial superinfection of perianal excoriations
- Granuloma formation
- Extraintestinal
- Urethritis
- Vulvovaginitis
- Pelvic inflammatory disease
Additional Reading
- American Academy of Pediatrics. Pinworms infection (Enterobius vermicularis). In: Pickering LK, Baker CJ, Kimberlin DW, et al, eds. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012.
- Arca MJ, Gates RL, Groner JI, et al. Clinical manifestations of appendiceal pinworms in children: an institutional experience and a review of the literature. Pediatr Surg Int. 2004;20(5):372 " 375. [View Abstract]
- Burkhart CN, Burkhart CG. Assessment of frequency, transmission, and genitourinary complications of enterobiasis (pinworms). Int J of Dermatol. 2005;44(10): 837 " 840. [View Abstract]
- Elston DM. What 's eating you? Enterobius vermicularis (pinworms, threadworms). Cutis. 2003;71(4):268 " 270. [View Abstract]
- Grencis RK, Cooper ES. Enterobius, Trichuris, Capillaria, and hookworm including Ancylostoma caninum. Gastroenterol Clin North Am. 1996;25(3):579 " 597. [View Abstract]
- Stermer E, Sukhotnic I, Shaoul R. Pruritus ani: an approach to an itching condition. J Pediatr Gastroenterol Nutr. 2009;48(5):513 " 516. [View Abstract]
Codes
ICD09
ICD10
SNOMED
- 266162007 Enterobiasis (disorder)
FAQ
- Q: Could the child have acquired pinworms from a pet dog or cat?
- A: No. Household pets are not involved in the life cycles of pinworms.
- Q: When can an infected child return to day care?
- A: After receiving the 1st treatment dose, the child can return to school or day care. It is prudent to bathe the child and to trim and scrub his or her nails prior to school reentry.
- Q: Is it necessary to reevaluate and retest a child once treated?
- A: No. However, reinfection is common.
- Q: Can pinworm eggs survive on bedding, toilet seats, or clothing?
- A: Yes. Eggs can remain infectious in an indoor environment for up to 3 weeks.
- Q: Does pinworm infection cause nocturnal bruxism?
- A: There is no proof of any causal relationship.
- Q: How do the anthelminthic medications work?
- A: They inhibit microtubule function and cause glycogen depletion in the adult worms.