Enterobiasis
Enterobiasis is a common parasitic infection caused by pinworms, specifically *Enterobius vermicularis*, which primarily affects the large intestines. This infection is most prevalent among children and is widely distributed across the globe, particularly in cooler and temperate regions. The infection occurs through several transmission routes, including direct hand-to-mouth contact with eggs, exposure to contaminated objects, and even inhalation of airborne eggs. The hallmark symptom of enterobiasis is intense itching in the anal area, particularly at night, when female worms migrate to deposit eggs.
While many cases can be asymptomatic, symptoms may also include abdominal pain, weight loss, and sleep disturbances due to itching. Diagnosis typically involves the microscopic identification of eggs collected using cellulose tape from the perianal area. Treatment usually involves medications like albendazole or mebendazole, and it is important to maintain good personal hygiene and sanitation to prevent reinfection. Effective prevention strategies also include frequent handwashing and laundering of clothing and bed linens, although complete prevention is considered unrealistic.
Enterobiasis
Anatomy or system affected: Gastrointestinal system, genitalia, intestines, skin
Also known as: Pinworm infection, pinworms
Definition
Enterobiasis is a parasitic infection of the large intestines by pinworms ( Enterobius vermicularis), which are small white roundworms, or nematodes. Enterobiasis is most endemic to children. Pinworm infection is globally distributed with a higher prevalence in cool and temperate climates. It is the most common parasitic worm infection found in the United States.
Causes
Infection is possible from direct hand-to-mouth transmission when fingers come into contact with eggs either from scratching or from touching clothing containing live eggs; from exposure to contaminated objects, such as clothing, linens, or toys; from inhalation of airborne eggs; and from retroinfection, when the eggs hatch on the perianal skin and the larvae travel up the colon.
Once ingested, the eggs will take one to two months to reach sexual maturation. Males typically die after reproduction and females usually die after laying eggs. The intense itching in the perianal and perineal area of the skin occurs during the females’ nighttime migration through the anus to deposit eggs. A person is considered infected as long as a female worm is depositing eggs.
Risk Factors
Scratching because of the itching tends to cause reinfection from hand-mouth transmission. Intense itching may also lead to bacterial skin infections from scratching. In severe cases, enterobiasis may cause appendicitis or intestinal blockage. Rarer complications include urinary tract infections and vulvovaginitis.
Symptoms
The hallmark symptom of enterobiasis is the nighttime itching around the perianal and perineal area. Itching is caused by the migration of the female worm to deposit eggs. The itching often results in sleep disturbance and in some cases may lead to severe skin infections from scratching. Other symptoms that may be seen, especially in children, include nervousness, abdominal pain, vomiting, weight loss, and enuresis. It is not uncommon, however, for enterobiasis to be asymptomatic.
Screening and Diagnosis
Diagnosis is made by microscopic identification of the thick-shelled, ovoid eggs. Cellulose tape is used to collect samples of eggs by pressing the tape against the perineal area. The tape preparation is then used to prepare a slide to view under a microscope. Worms may also be visible. The collection of eggs with the tape may need to be taken over several consecutive days. Eggs are not typically observed in the stools.
Treatment and Therapy
The treatment of choice is chemotherapy with albendazole or mebendazole given in a single dose and repeated in two weeks. Pyrantel pamoate (available without a prescription) and piperazine may also be used. To avoid reinfection, one should seek counseling to discuss personal hygiene and environmental sanitation. Family members should also be treated, and the living environment should be decontaminated by washing bed linens and clothing.
Prevention and Outcomes
The best method of preventing enterobiasis is good personal hygiene that includes daily bathing and frequent handwashing. Using well-laundered (in hot water) clothing and bed linens can also help to reduce and prevent reinfection. Sunlight and ultraviolet lamps will destroy eggs, and dry heat is useful in sterilizing metal toys. Eggs are not killed by swimming pool chlorine, however. Health experts believe that total prevention is unrealistic.
Bibliography
Centers for Disease Control and Prevention. “Pinworm Infection (Enterobiasis).” Available at http://www.cdc.gov/ncidod/dpd/parasites/pinworm.
Despommier, Dickson D., et al. Parasitic Diseases. 5th ed. New York: Apple Tree, 2006.
“ Enterobius vermicularis.” In Human Parasitology, edited by Burton J. Bogitsh, Clint E. Carter, and Thomas N. Oeltmann. 3d ed. Boston: Academic Press/Elsevier, 2005.
“Intestinal Nematodes.” In Diagnostic Medical Parasitology, edited by Lynne Shore Garcia. 5th ed. Washington, D.C.: ASM Press, 2007.
Kucik, Corry Jeb, et al. “Common Intestinal Parasites.” American Family Physician 69 (2004): 1161-1168.
Rett, Doug. “ Enterobius vermicularis.” University ofMichigan, Museum of Zoology. Available at http://animaldiversity.ummz.umich.edu/site/index.html.
Shorey, Harsha, Beverley-Ann Biggs, and Peter Traynor. “Nematodes.” In Manual of Clinical Microbiology, edited by Patrick R. Murray et al. 9th ed. Washington, D.C.: ASM Press, 2007.