Enterobiasis

Essentials of Diagnosis

• Nocturnal perianal pruritus

• Identification of eggs or adult worms on perianal skin or in stool

General Considerations

• Enterobiasis is transmitted person-to-person via

  • Ingestion of eggs after contact with the hands or perianal region of an infected individual

  • Food or fomites that have been contaminated by an infected individual

  • Infected bedding or clothing

• Autoinfection also occurs

• Eggs hatch in the duodenum and larvae migrate to the cecum

• Females mature in about a month and remain viable for about another month

• During this time they migrate through the anus to deposit large numbers of eggs on the perianal skin

• Due to the relatively short lifespan of these helminths, continuous reinfection is required for long-standing infection

Demographics

• Enterobius vermicularis is common cause of intestinal infections worldwide, with maximal prevalence in school-age children

Symptoms and Signs

• Most persons are asymptomatic

• Perianal pruritus is common, particularly at night due to the presence of the female worms or deposited eggs

• Insomnia, restlessness, and enuresis are common in children

• Perianal scratching may result in excoriation and impetigo

• Mild gastrointestinal symptoms have also been attributed to enterobiasis, but associations are not proven

• Serious sequelae are uncommon

• Rarely, worm migration results in inflammation or granulomatous reactions of the gastrointestinal or genitourinary tracts

• Colonic ulceration and eosinophilic colitis have been reported

Differential Diagnosis

• Tinea or candidiasis of the anogenital region

• Hemorrhoids

• Proctitis

• Contact dermatitis

• Strongyloidiasis

• Anal fissure

• Idiopathic anogenital pruritus

Laboratory Tests

• Pinworm eggs are usually not found in stool

• Diagnosis is made by finding adult worms or eggs on the perianal skin

• A common test is to apply clear cellophane tape to the perianal skin, ideally in the early morning, followed by microscopic examination for eggs

• The sensitivity of the tape test is reported to be about 50% for a single test and 90% for three tests

• Nocturnal examination of the perianal area or gross examination of stools may reveal adult worms, which are about 1 cm in length

• Eosinophilia is rare

Medications

• Single oral doses of albendazole (400 mg), mebendazole (100 mg), or pyrantel pamoate (11 mg/kg, to a maximum of 1 g)

• The dose is repeated in 2 weeks due to frequent reinfection

Therapeutic Procedures

• Other infected family members or contacts should be treated concurrently

• Treatment of all close contacts may be appropriate when rates of reinfection are high in family, school, or institutional settings

• Standard handwashing and hygiene practices are helpful in limiting spread

• Perianal scratching should be discouraged

• Washing of clothes and bedding should kill pinworm eggs

Complications

• Rarely, worm migration—including migration through the female genital tract or into the urethra—results in ectopic inflammation (vulvovaginitis, diverticulitis, appendicitis, cystitis) or granulomatous reactions (colon, genital tract, peritoneum, and elsewhere)

• Colonic ulceration and eosinophilic colitis have been reported

Prognosis

• Although annoying, the infection is usually benign

• Cure is readily attainable with one of several effective drugs

• Reinfection is common because of continued exposure outside the home

When to Refer

• Inability to cure the infection

• No response or progression of symptoms despite therapy