Enterobius vermicularis - Clinical Manifestation, Complications, Prognosis, Epidemiology, Reservoir, Transmission
Clinical Manifestations of Enterobius vermicularis
In the majority of cases (one-third), enterobiasis caused by Enterobius vermicularis remains asymptomatic.
Intestinal enterobiasis
In symptomatic cases, the common clinical manifestation of Enterobius vermicularis infection is perianal and perineal pruritus (pruritus ani) which occurs in the early morning or is nocturnal. Other syndromes include irritability, abdominal pain, and restlessness which are caused by female parasites laying eggs on the host anal area.
In severe cases of pinworm infection, symptoms include behavioral changes such as sleep disturbances, nail-biting, grinding teeth at night, neurosis, etc. In children, symptoms may vary from appetite loss, weight loss, emotional instability, and bed wetting.
If the intensity of itching is high, continuous scratching of the area may result in secondary bacterial infections such as bacterial skin inflammation, and hair follicle inflammation.
Extra-Intestinal enterobiasis
Although the parasite is not able to damage the host skin and does not migrate through tissues, it can move through the vulva, vagina, uterine cavity, fallopian tubes, ovaries, and peritoneal cavity. They can result in inflammation of the vulva and vagina resulting in vaginal discharge and itchiness of the vulva.
As pinworms can also enter the urethra, they carry intestinal bacteria with them which results in urinary tract infections.
The adult Enterobius vermicularis may also cause appendicitis but it is still debated.
Complications of Enterobius vermicularis
Complications caused by Enterobius vermicularis include:
urethritis
endometritis
vulvovaginitis
salpingitis
prostatitis
impetigo or excoriation due to continuous perineal scratching
Prognosis of Enterobius vermicularis
Infection by Enterobius vermicularis can be cured with proper treatment (90% of cases). Although rarely fatal, reinfection is common.
Epidemiology of Enterobius vermicularis
Epidemiological studies have reported that Enterobius vermicularis is worldwide in distribution. However, the prevalence rate is higher in temperate regions than in the tropics.
Reservoir, Source of Enterobius vermicularis
Humans are the only natural host of Enterobius vermicularis. There are no animal reservoirs for the parasite.
Human feces are the most common source of infection while surfaces such as soiled beds, table tops, bathroom fixtures, door knobs, and urine are other important sources of infection.
Transmission of Enterobius vermicularis
Enterobius vermicularis occurs in school or preschool children, individuals living in crowded conditions, or with poor personal hygiene.
Transmission of Enterobius vermicularis occurs via the following routes:
oral route – ingestion of infectious eggs by inadequate hand washing or nail biting
swallowing of airborne eggs present in dust which is rare
autoinfection – ingestion of eggs from the anus to the mouth via soiled fingers, most common in children
handling of contaminated surfaces such as soiled beds, table tops, bathroom fixtures, door knobs, urine, linen
retro-infection – unsual mode of infection seen in adults
* larvae hatching from the eggs are deposited on the perianal and perineal skin and migrate back to the intestine where they develop into adult pinworms, sexually mature, and lay eggs