Enterobiasis is a common parasitic disease caused by Enterobius vermicularis (pinworms) that inhabit the distal small intestine, cecum, and colon. It predominantly affects young children and is characterized clinically by nighttime itching around the perineum and anus, as well as disturbed sleep.
Etiology and Epidemiology
Pinworms, also known as Enterobius vermicularis, are thread-like, white nematodes. Adult male worms measure 0.2–0.5 cm, while female worms are 0.8–1.3 cm in length. The eggs are asymmetrical and oval-shaped. The worms are dioecious, with males dying shortly after mating. Adult worms parasitize the cecum, colon, and distal ileum in humans and survive for 2–4 weeks, with a typical lifespan of less than 2 months. Female worms migrate to the lower intestinal tract, and during sleep, when the anal sphincter relaxes, they emerge from the anus to lay eggs in response to changes in temperature, humidity, and air exposure. Most female worms die after laying eggs, although some may re-enter the anus, vagina, urethra, or other locations, leading to ectopic damage. Eggs become infective about 6 hours after being deposited around the anus. Self-infection occurs when eggs contaminate a child’s fingers and are then ingested.
Pinworm eggs are highly resistant and can survive for about 3 weeks indoors. Eggs may contaminate clothing, bedding, toys, and food, spreading through ingestion or airborne inhalation.
Humans are the only source of transmission, and infection is spread via the fecal-oral route. The general population is susceptible, with transmission commonly occurring in daycare settings and households. Enterobiasis is globally distributed, with infection rates higher in children than adults, particularly in children living in group settings.
Clinical Presentation
The incubation period is approximately 1–2 months. Pinworm infection causes both localized and systemic symptoms. The most common symptom is intense itching of the perianal and perineal skin, accompanied by disturbed sleep. Local scratching may lead to dermatitis and secondary infections. Systemic symptoms include gastrointestinal irritation, such as nausea, vomiting, abdominal pain, diarrhea, and loss of appetite. Psychological symptoms such as anxiety, insomnia, night terrors, irritability, and difficulty concentrating may also occur. Occasionally, ectopic migration of pinworms to other organs or adjacent structures can lead to appendicitis, vaginitis, pelvic inflammatory disease, or peritonitis.
Laboratory Examinations
Complete Blood Count
Eosinophilia may be observed.
Pathogen Detection
Adult worms can be identified by inspecting the perianal area or underwear 1–3 hours after the child falls asleep, where white, thread-like worms may be visible.
Eggs can be detected using the morning stool sampling method or by using a cotton swab or transparent adhesive tape to collect samples from the perianal area before defecation or bathing. These can then be examined under a low-power microscope. Sampling over 3 consecutive days yields a high detection rate.
Diagnosis and Differential Diagnosis
Symptoms such as anal itching and disturbed sleep should raise suspicion for enterobiasis, and the presence of adult worms or eggs confirms the diagnosis. Ectopic migration of pinworms leading to inflammation in specific locations requires differentiation from other pathogen-induced inflammations, such as bacterial urethritis or vaginitis. Diagnostic differentiation can be supported by bacterial cultures from vaginal secretions or urine samples.
Treatment
Anthelmintic Therapy
Pyrvinium Embonate
Pyrvinium embonate is the drug of choice for pinworm infection. The recommended dose is 5 mg/kg (maximum dose of 0.25 g), taken as a single dose before bedtime. Treatment is repeated after 2–3 weeks. Adverse effects are mild and may include abdominal pain, diarrhea, nausea, and vomiting. Rare cases of hypersensitivity or muscle spasms have been reported. The drug may temporarily color stools red.
Pyrantel Pamoate
Pyrantel is a broad-spectrum, highly effective anthelmintic drug with minimal absorption when taken orally. The recommended dose is 11 mg/kg (maximum dose of 1 g), taken as a single dose before bedtime, with a second dose repeated after 2 weeks. Adverse effects are mild and include nausea, dizziness, and abdominal pain. Patients with severe peptic ulcers should use this drug cautiously.
Mebendazole
The dosage and administration are the same as those used for Ascaris therapy, with treatment repeated after 2 weeks.
Topical Therapy
Perineal and perianal areas can be washed every night before bedtime, and pinworm ointment (containing 30% Stemona extract and 0.2% gentian violet) can be applied to kill worms and relieve itching. Pyrantel suppositories inserted into the anus for 3–5 consecutive days may also be used.
Prevention
Preventive measures include cultivating good hygiene habits, such as washing hands before meals and after defecation, cutting nails frequently, and avoiding finger-sucking habits. Infants and young children can wear one-piece garments to minimize self-contamination. Toys, utensils, and bedding should be regularly cleaned and disinfected. Prognosis for enterobiasis is excellent.