COMMUNITY HEALTH: VULVOVAGINITIS FROM ENTEROBIASIS

                       VULVOVAGINITIS FROM ENTEROBIASIS

                               Role of finger sucking in pinworm autoinfection

        Enterobiasis is a human parasitic disease caused by Enterobius vermicularis, commonly called pinworm. Pinworm infection occurs worldwide. It is the most common helminth infection in the United States and Western Europe. Pinworm is therefore an exception to the tenet that intestinal parasites are uncommon in affluent communities. Pinworm infection is more common in whites than in coloured people (blacks). It is more prevalent in children than in adults. Because it spreads from host to host through contamination, pinworms are common among people living in close contact and tend to occur in all people within a household.  Finger sucking and nail biting has been shown to increase both the incidence and relapse rates. Humans are the only species that can transfer this parasite. Household pets like dogs and cats cannot become infected with human pinworms.

         The entire life cycle – from egg to adult – takes place in the human gastrointestinal tract. Ingested pinworm eggs hatch in the duodenum and release pinworm larvae. The larvae moult twice and become adults as they migrate towards the ending of the small intestine. The male and female pinworms mate in the ileum where after the male worms die. The gravid female pinworms settle in the ileum, caecum, appendix and the ascending colon where they attach themselves to the mucosa and ingest colonic contents. They then migrate from the colon to the rectum. When the infected individual is asleep at night, because the body temperature is low and there is less movement, the female pinworms emerge from the anus to obtain oxygen necessary for the maturation of the eggs. While moving on the skin near the anus, the female pinworms deposit eggs.  After depositing the eggs, the female worm becomes opaque and dies.  Meanwhile, the deposited eggs are sticky and gets stuck on the perianal skin, underwear, or bedding and becomes infective within a few hours. Despite the limited 13 weeks life span of individual pinworms, autoinfection (i.e. infection from original host to itself) either from the anus to the mouth route or other means, causes the pinworms to sometimes inhabit the same host indefinitely.

        Although about one third of pinworm infected persons are asymptomatic, the most common presentation is pruritus ani (itching around the anus). The itching occurs mainly during the night and is caused by the female worms migrating to lay eggs around the anus. Both the migrating females and the clumps of eggs are irritating but the exact mechanisms causing the intense pruritus have not been explained. Pruritus and discomfort can lead to secondary reflex symptoms of insomnia, bruxism and restless. The itching also leads to continuously scratching the area around the anus which can result in tearing of the skin thereby leading to secondary infections like bacterial dermatitis and folliculitis. A considerable proportion of children suffer from anorexia, weight loss and irritability. There can be abdominal pain . Pinworms can be found in the appendix where they can cause appendicitis.

       Pinworms cannot damage the skin and they do not normally migrate through tissues. However, in women, they may move onto the vulva and into the vagina and from there moving to the uterine cavity, fallopian tubes, ovaries, and peritoneal cavity. This can cause vulvovaginitis leading to vaginal discharge and pruritus vulvae.

        Diagnosis can usually be made from the clinical presentation and investigations. The pinworms can be sought in the perianal region two to three hours after the infected person is asleep. The Graham Scotch adhesive tape swap can be used in younger children. Since anal itching is a common symptom of pinworm infestation, an infected person who has scratched the anal area may have picked up some pinworms under the nails that could be used for diagnosis under a microscope.  Because pinworms do not lay eggs in faeces and since pinworms and their eggs are often sparse in stool, routine examination of faecal material is therefore of little diagnostic use and is not recommended.

        Medications used for treatment are mebendazole, albendazole or pyrantel palmoate. The drugs are usually given in one dose at first and then another single dose two weeks later.

         Prevention and control of pinworm infection include washing the hands with soap and water after using the toilet, changing diapers, and before handling food.