Enterobiasis, also known as oxyuriasis or pinworm infection, is a common, contagious helminthic infestation caused by the nematode Enterobius vermicularis that mainly affects children and institutionalized persons. The disease is spread by fecal-oral and air-borne route while reinfection is common. Family members of the affected individuals often become infected, as well.
Enterobiasis may be asymptomatic and diagnosed incidentally, with worms being observed in the perineal area. If any, symptoms consist of anal and/or vulvar pruritus, that may be very intense and constitute the main complaint. Scratching may lead to the appearance of excoriations, that sometimes become infected by bacteria. The perineum, anus or genitals may be erythematous or, in more severe cases, eczematous dermatitis may be diagnosed . Furthermore, patients may have severe abdominal pain similar to that found in acute appendicitis , may be irritable and have nocturnal enuresis. Sleep is disturbed in this disease primarily because of the pruritus. Girls may present with vaginitis. Children may also develop teeth grinding, with subsequent dental consequences. Other possible symptoms and signs include inappetence, nausea, and vomiting.
If Enterobius vermicularis migrates into the female genital tract, it may cause uterus, ovary, fallopian tubes, or peritoneum granulomas . Dissemination of the disease has also been described in the prostate, perianal tissue , epididymis , lungs , urinary bladder, spleen, liver, and conjunctival sac.
Parents may report seeing parasites on the child's perineum or on the surface of the feces. Female parasites are thin, white, about 10 mm long, while male parasites are half that size. Eggs can be found on the patient's perineum in the morning and can be captured if the transparent tape is placed on the area before the child bathes . The next step is to observe them under a microscope. Eggs are described as ovoid and flat on one side. Samples should be obtained on three to five consecutive mornings . Less reliable diagnostic methods are analyzing samples obtained from under the child's fingernails or asking the parent to inspect the perineal area of the child a few hours after he or she has fallen asleep, in order to observe live parasites. Stool samples are not routinely examined because eggs and adult parasites are seldom observed by this method.
In complicated cases, when granulomas are formed and need to be excised, they also can be studied. A histological analysis reveals inflammatory infiltrates, giant cells, lymphocytes, and numerous eosinophils. All these elements, in addition to fibrous tissue and necrotic material, are present around calcified parasite eggs . A nodule that does not need to be excised can be punctured by fine needle aspiration . In endemic areas, appendices excised for various reasons should also be analyzed . Blood workup is usually noncontributory in uncomplicated cases, as eosinophilia is absent.
Enterobiasis is thought to be underreported, therefore its morbidity is difficult to be established .