Disease. Enterobiasis also called pinworm infection is a common, contagious, parasitic infestation found mainly in children. Enterobiasis is caused by Enterobius vermicularis (parasitic pinworm). This infection rarely causes any serious physical problems except for the main symptom, which is severe rectal itching. Enterobiasis is contracted by ingesting the eggs of pinworms, which may be carried on fingernails, clothing, toys or bedding. The eggs may also be inhaled in the dust. The infection may be transmitted to others by hand-to-mouth contact with contaminated food or objects.
Species. Enterobius vermicularis (E. vermicularis) is a small white worm with thread-like appearance. E. vermicularis is a common intestinal parasite of humans, called pinworm in the United States and threadworm in the United Kingdom. It has a worldwide distribution with approximately 200 million people infected, most of them being children. The male measures 5 cm in length. The posterior end is curved and carries a single copulatory spicule. The female measures 13 cm in length. The posterior end is straight. The infective stage of this species is by ingestion of eggs containing larvae with contaminated raw vegetables. The mode of infection is by direct infection from a patient (Fecal-oral route).
Development E. vermicularis has a monoxenous life cycle. Fertilized females and males die soon after mating – live in the lower part of the small intestine (ileum) and in the cecum, appendix, and ascending colon of the large intestine, where they are attached to the mucosa. At lasting 3–6 weeks, the end of their life, the gravid females migrate to the rectum and emerge from the anus where they lay their eggs (11,000–16,000 per female). The worm then dies and the eggs have a sticky surface and tend to adhere to the perianal folds.
Infection, Epidemiology. Autoinfection is a typical trait of E. vermicularis, occurring mainly in children. The migration of female worms to the anus and the deposition of eggs cause intensive itching, mainly at night. Scratching and the resulting anus-finger-mouth contact leads to continual reinfection. In addition, the highly infective eggs may contaminate all household objects and infect whole families. Often, infections are observed in cramped conditions and where hygiene conditions are poor. The second mode of infection is possible by the hatching of third-stage larvae on the anal mucosa and migration backward to the intestine. This retro-infection potentially leads to a heavy parasite load.
Diagnostic. Diagnosis can be done in two way, namely eggs in stool and per-anal swab. Examination of the stool by direct saline smear to detect the egg: this is positive in about 5% of cases because the eggs are glued to the peri-anal skin. And then, the peri-anal region is swabbed with a piece of adhesive tape (cellotape) hold over a tongue depressor. The adhesive tape is placed on a glass slide and examined for eggs. The swab should be done in the early morning before bathing and defecation.
Pathology, Treatment Symptoms are caused by the nocturnal egg-laying of the females, which result in fierce itching. The night-long scratching, especially in children, with resulting sleep deprivation, may cause pallor, impairment of con-centration, irritability, and decreased school performance. Worms can also invade the appendix, vagina, or fallopian tubes and cause inflammation. Treatment with appropriate drugs is possible but has to be applied to the whole family or household. The available treatment for Enterobiasis are by mebendazole and piperazine.
References:
Dawit A., Ephrem K., S. Nagesh, Solomon G., Fetene D., Jemal A. Medical Parasitology. USAID collaboration with Ethiopia Public Health Training Initiative, The Carter Center, the Ethiopia Ministry of Health, and the Ethiopia Ministry of Education. 2006.
Lucius R., Brigitte Loos-Frank, Richard P.L., Robert P., Craig W.R., and Richard K.G. The Biology of Parasites. Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim, German: 2017.
Sun Huh and Bronze, M.S. Pinworm (Enterobiasis). [Updated: Nov 21, 2018]. Available from: https://emedicine.medscape.com/article/225652-overview
