Enterobius vermicularis

1-2-5. Enterobius vermicularis in its adult form

3-4. Enterobius vermicularis eggs on human feces

  • The nematode (roundworm) Enterobius vermicularis (previously Oxyuris vermicularis) also called human pinworm. (Adult females: 8 to 13 mm, adult male: 2 to 5 mm. )  Humans are considered to be the only hosts of E. vermicularis. A second species, Enterobius gregorii, has been described and reported from Europe, Africa, and Asia. For all practical purposes, the morphology, life cycle, clinical presentation, and treatment of E. gregorii is identical to E. vermicularis.

Life cycle

  • Eggs are deposited on perianal folds . Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area . Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g. , curtains, carpeting). Some small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs. Following ingestion of infective eggs, the larvae hatch in the small intestine  and the adults establish themselves in the colon . The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months. Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area . The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions . Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown.
  • A person infected with pinworm is often asymptomatic, but itching around the anus is a common symptom. Diagnosis of pinworm can be reached from three simple techniques. The first option is to look for the worms in the perianal reqion 2 to 3 hours after the infected person is asleep. The second option is to touch the perianal skin with transparent tape to collect possible pinworm eggs around the anus first thing in the morning. If a person is infected, the eggs on the tape will be visible under a microscope. The tape method should be conducted on 3 consecutive mornings right after the infected person wakes up and before he/she does any washing. Since anal itching is a common symptom of pinworm, the third option for diagnosis is analyzing samples from under fingernails under a microscope. An infected person who has scratched the anal area may have picked up some pinworm eggs under the nails that could be used for diagnosis.

All photos taken by me

Enterobiasis (Pinworm)

Enterobiasis is one of the most common helminthic infection. It is a nematode (roundworm) intestinal infection and is caused by the Enterobiasis vermicularis worm. The female nematode is sized 10 mm x 0.7 mm, and the male are smaller.

Epidemiology in the World and Indonesia

3% of school children in the Sukaraja district, West Java (1995)

4.54% of women emigrating as foreign workers (2006)


E. vermicularis is an obligate parasite and human are the only natural host. Transmission are through fecal-oral contamination via hand-mouth contact or via fomites (object capable of carrying infectious organisms ex: hair, toys and clothes). After ingestion the eggs usually hatch in the duodenum within 6 hours. The maturation of the worms are 2 weeks with a life span of about 2 months. 

Adult worms usual inhabit the terminal illeum, cecum, vermiform appendix, and proximal ascending colon. They live free in the intestinal lumen. After copulation, the female migrates to the rectum and perineum (usually at night) and lay about 11,000 eggs. The eggs are infectious within 6-8 hours and may remain infectious in the environment for as long as 3 weeks.

Clinical manifestation

Usually asymptomatic. The typical manifestation is nocturnal pruritus ani that is caused by hypersensitivity to the antigens of the worms. Other signs : dermal “tingling”, in women, migration to the vulva may cause vaginal itching and pain that can lead to vulvovaginitis infection and urinary tract infection.


Usually diagnosed by applying tape on the perineal/anal region in the morning, then looking through glass side for microscopy. It will look like this : 

Credit photo : http://parasitologyillustrated.com/classes_of_parasites/nematodes/e_vermicularis.html

In blood studies will find eosinophillia, but is rarely found.

if there are abdominal pain or diarrhea it suggests co-infection with Dientamoeba fragilis.


Though they may be rare, some complications found are : salpingitis, vulvovaginitis (not that rare in women), oophoritis, cystitis, peritonitis, urethritis, prostatitis, and bartholin gland abcsess.


The main focus of the treatment are :

  1. Antihelminthic
  2. Symptomatic (antipruritic)
  3. Hygiene care
  4. Diagnosing & treating family members in the same household

1. Antihelminthic

The 1st line are : Albendazole, Mebendazole, and Pyrantel Pamoat (Combantrin).

The dosage are all single dose, and then will be repeated 2 weeks after the first dose.The dosage is : albendazole 400 mg orally, Mebendazole 100 mg,or Pyrantel permeate 11 mg/kg (maximum dose 1 g). 

Mechanism of action :

  1. Mebendazole : selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine. Causes death of worms, but not eggs.
  2. Albendazole : inhibits tubulin polymerization, resulting in degeneration of cytoplasmic microtubules. Decreases ATP production causing energy depletion, immobilization, and then death. Causes death of worms, but not eggs.
  3. Pyrantel pamoat : depolarizing neuromsucular blocking agen and inhibits cholinesterases causing spastic paralysis of the worm

2. Symptomatic : antipruritic cream in the itching region

3. Hygiene must be increased :

  •  Laundry underwear and bed linens everyday with hot water and followed by hot dryer to kill eggs.
  • Always bring a hand sanitizer with you and clean your hands before and after eating, before and after changing clothes, before and after going to the bathroom (especially).
  • Vacuum your room and house regularly.

4. It is recommended that if there are more than 1 people with symptoms in a household, everyone must consume antihelminthics with the same dosage as the positive patients. 

Literature :

  1. Sweet RL, Gibbs RS. Infectious Disease of the Female Genital Tract. 
  2. Lerger, S. Infectious Diseases of Indonesia. 2015
  3. Wolfram W. Enterobiasis. Medscape
  4. Bayless TM, Diehl A. Advanced Therapy in Gastroenterology and Liver Disease. 

See that “social worm”? We did cellulose tape perianal swab to check if there are worms on the anal area. Shalaaa! Live and moving #pinworm #parasitology #laboratory #enterobiasis

Pinworms – Causes, Symptoms, Diagnosis, Treatment and Ongoing care

Basics Description Intestinal infection with Enterobius vermicularis, characterized by perineal and perianal itching, usually worse at night System(s) affected: GI; Skin/Exocrine Synonym: Enterobiasis Epidemiology Predominant age: 5–14 years Prevalence Most common helminthic infection in US, w…
Pinworms – Causes, Symptoms, Diagnosis, Treatment and Ongoing care

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See that “social worm”? We did cellulose tape perianal swab to check if there are worms on the anal area. Shalaaa! Live and moving #pinworm #parasitology #laboratory #enterobiasis

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