Enterobius/Enterobiasis

Enterobiasis is a helminth infection caused by Enterobius vermicularis, also known as a pinworm. This infection is typically seen in children and is transmitted through the fecal–oral route. The primary clinical feature is anal pruritus, but patients are often asymptomatic. Visualization of ova or worms on cellophane tape testing is often required for diagnosis. Anthelmintic medications are used for treatment. Prevention of reinfection and transmission requires frequent handwashing and bathing, as well as washing of clothes and linens.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Table of Contents

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General Characteristics and Epidemiology

Basic features of Enterobius

  • Nematode 
  • Appearance:
    • White 
    • Slender 
    • Pointed tail
  • Size: 
    • Females: 8–13 mm long
    • Males: 2–5 mm long
  • Eggs:
    • Elongated
    • Flattened on 1 side
    • Translucent

Clinically relevant species

Enterobius vermicularis, or pinworm, causes enterobiasis.

Epidemiology

Enterobiasis is the most common helminth infection in the United States and Western Europe.

  • Prevalence: 
    • United States: 5%–15% of the general population (approximately 40 million people)
    • Worldwide: 60 million to 100 million infections annually
  • Children > adults
  • Men > women

Pathogenesis

Reservoir

Humans are the primary hosts of E. vermicularis.

Transmission

  • Fecal–oral
  • Contact with contaminated surfaces and fomites

Host risk factors

  • Disabled persons
  • Schoolchildren
  • Prisoners
  • Healthcare, school, and prison workers

Life cycle

The entire life cycle of E. vermicularis takes place in the human GI tract.

  • Ingestion of eggs → hatch and release larvae in the small intestine Small intestine The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine
  • Adult worms reside in the cecum, appendix, and ascending colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix.
  • Female worms migrate through the rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal (usually at night)  → deposit eggs on perianal skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin 
  • Inflammatory reaction to worms and eggs on skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin → intense pruritus
  • Autoinfection occurs by patients transferring the eggs to the mouth with contaminated hands after scratching the affected region.
  • Environmental contamination may also occur via the consumption of contaminated foods or contact with surfaces that are contaminated with eggs.

Clinical Presentation

  • Enterobiasis is often asymptomatic.
  • Most common presentation: perianal itching (pruritus ani)
    • More severe at night
    • Excoriation from scratching can lead to secondary bacterial infections.
  • Rare symptoms indicative of a high worm burden: 
    • Abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Nausea and vomiting
  • Rare extraintestinal manifestations:
    • Vulvovaginitis Vulvovaginitis The term vulvovaginitis is used to describe an acute inflammation of the vulva and vagina. Vulvovaginitis can be caused by several infectious and non-infectious etiologies, and results from disruption of the normal vaginal environment. Common signs and symptoms include pain, pruritis, erythema, edema, vaginal discharge and dyspareunia. Vulvovaginitis
    • Salpingitis
    • Oophoritis
    • Cervical granuloma
    • Peritoneal inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation

Diagnosis and Management

Diagnosis

  • Visual inspection of mobile worms:
    • Near the anus
    • On clothing or bed linens
  • Cellophane tape test (often called the “Scotch tape test”):
    • Apply an adhesive tape–like material to the perianal region.
    • Eggs will accumulate on the adhesive surface.
    • Examination of the tape under the microscope may show ova or worms.
    • Improved yield at night or first thing in the morning
Photomicrograph enterobius vermicularis eggs enterobiasis

Photomicrograph of 8 Enterobius vermicularis eggs on cellophane tape

Image: Photomicrograph depicts eight eggs of the human pinworm, Enterobius vermicularis” by CDC. License: Public Domain

Management

Medical therapy:

  • Anthelmintic medications: 
    • Mebendazole
    • Pyrantel pamoate
    • Albendazole
  • Family members and classmates of the patient should be treated (owing to the high transmission rate).

Measures to reduce reinfection and spread:

  • All linens and clothing should be washed.
  • Frequent handwashing and bathing
  • Clip fingernails.

Comparison of Similar Helminths

Table: Comparison of similar helminths and their associated diseases
Organism Enterobius vermicularis Toxocara Toxocara Toxocariasis is caused by the nematodes Toxocara canis and T. cati. These species frequently infect dogs and cats and are most commonly transmitted to humans via accidental ingestion of eggs through the fecal-oral route. Toxocara are not able to complete their life cycle in humans, but they do migrate to organs (including the liver, lungs, heart, brain, and eyes), where they cause inflammation and tissue damage. Toxocariasis canis Ascaris Ascaris Ascaris is a genus of parasitic nematodes. The infection, ascariasis, is most often caused by A. lumbricoides. Transmission occurs primarily via ingestion of water or food contaminated with Ascaris eggs. Most patients with ascariasis are asymptomatic. Ascaris/Ascariasis lumbricoides Strongyloides stercoralis Schistosoma Schistosoma Schistosomiasis is an infection caused by Schistosoma, a trematode. Schistosomiasis occurs in developing countries with poor sanitation. Freshwater snails are the intermediate host and are transmitted to humans through skin contact with contaminated fresh water. The clinical presentation occurs as a result of the host's immune response to antigens from the eggs. Schistosoma/Schistosomiasis mansoni
Characteristics Nematode Nematode Nematode Nematode Trematode
Reservoir Humans Dogs Humans
  • Humans
  • Dogs
  • Cats
Humans
Transmission Fecal–oral Fecal–oral Fecal–oral Skin contact with contaminated soil Skin contact with contaminated water
Clinical
  • Pruritus ani
  • Abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and vomiting are less common.
  • Visceral larva migrans
  • Ocular larva migrans
  • Cough
  • Wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing
  • Hemoptysis Hemoptysis Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. Hemoptysis
  • Abdominal cramping
  • Nausea
  • Malnutrition Malnutrition Malnutrition is a clinical state caused by an imbalance or deficiency of calories and/or micronutrients and macronutrients. The 2 main manifestations of acute severe malnutrition are marasmus (total caloric insufficiency) and kwashiorkor (protein malnutrition with characteristic edema). Malnutrition in children in resource-limited countries
  • Cough
  • Wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing
  • Abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
  • Diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea
  • Rash
  • Swimmer’s itch
  • Katayama fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Chronic infections lead to granuloma formation causing brain, lung, intestinal, and liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver disease.
Diagnosis
  • Clinical
  • Cellophane tape test
  • Serology
  • Biopsy
Stool analysis
  • Stool analysis
  • Serology
  • Stool analysis
  • Serology
Management
  • Albendazole
  • Mebendazole
  • Pyrantel pamoate
  • Albendazole
  • Mebendazole
  • Albendazole
  • Mebendazole
  • Ivermectin
  • Albendazole
Praziquantel
Prevention Good hygiene
  • Good hygiene
  • Deworm dogs.
  • Proper disposal of dog feces
  • Good hygiene
  • Clean raw fruits and vegetables before consuming.
  • Wear shoes and protective clothing.
  • Improve sanitation.
  • Avoid swimming or bathing in contaminated water.
  • Drink boiled or bottled water.
  • Improve sanitation.

Differential Diagnosis

  • Proctitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the rectal mucosa that may be caused by inflammatory bowel disease, infectious organisms (e.g., Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella, Shigella Shigella Shigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir. Shigella), radiation, and ischemia: Symptoms include pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, tenesmus, itching, and bleeding. Diagnosis depends on physical exam, proctoscopy or colonoscopy, cultures, and biopsy. Management depends on the etiology and can include antibiotics and steroids.  
  • Psoriasis Psoriasis Psoriasis is a common T-cell-mediated inflammatory skin condition. The etiology is unknown, but is thought to be due to genetic inheritance and environmental triggers. There are 4 major subtypes, with the most common form being chronic plaque psoriasis. Psoriasis: chronic inflammatory skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin condition: Inverse psoriasis causes symmetric, smooth, shiny, and erythematous plaques in intertriginous areas, including the intergluteal region. Patients can experience pruritus, particularly at night. The diagnosis is clinical, and no eggs would be seen on a cellophane tape test. Management may include topical steroids, calcineurin inhibitors, vitamin D analogs, and emollients. Disease-modifying antirheumatic drugs Disease-modifying antirheumatic drugs Disease-modifying antirheumatic drugs are antiinflammatory medications used to manage rheumatoid arthritis. The medications slow, but do not cure, the progression of the disease. The medications are classified as either synthetic or biologic agents and each has unique mechanisms of action and side effects. Disease-modifying Antirheumatic Drugs and biologics may be used for severe cases.
  • Atopic dermatitis Atopic Dermatitis Atopic dermatitis, also known as eczema, is a chronic, relapsing, pruritic, inflammatory skin disease that occurs more frequently in children, although adults can also be affected. The condition is often associated with elevated serum levels of IgE and a personal or family history of atopy. Skin dryness, erythema, oozing, crusting, and lichenification are present. Atopic Dermatitis (Eczema): chronic inflammatory skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin disease, usually due to a combination of genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics, immunologic dysfunction, and environmental factors: Patients will have pruritus and erythematous lesions on flexural surfaces, but it can occur, rarely, in the gluteal region Gluteal region The gluteal region is located posterior to the pelvic girdle and extends distally into the upper leg as the posterior thigh. The gluteal region consists of the gluteal muscles and several clinically important arteries, veins, and nerves. The muscles of the gluteal region help to move the hip joint during walking, running, standing, and sitting. Gluteal Region. Diagnosis is based on history and exam, and the cellophane tape test will be negative for eggs. Management includes trigger avoidance, moisturizers, and topical steroids. 
  • Internal hemorrhoids Hemorrhoids Hemorrhoids are normal vascular cushions in the anal canal composed of dilated vascular tissue, smooth muscle, and connective tissue. They do not cause issues unless they are enlarged, inflamed, thrombosed, or prolapsed. Patients often present with rectal bleeding of bright red blood, or they may have pain, perianal pruritus, or a palpable mass. Hemorrhoids: dilated vessels of the hemorrhoidal plexus in the anal canal, commonly caused by constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation: Internal hemorrhoids Hemorrhoids Hemorrhoids are normal vascular cushions in the anal canal composed of dilated vascular tissue, smooth muscle, and connective tissue. They do not cause issues unless they are enlarged, inflamed, thrombosed, or prolapsed. Patients often present with rectal bleeding of bright red blood, or they may have pain, perianal pruritus, or a palpable mass. Hemorrhoids are painless, but pruritus can occur with prolapsed hemorrhoids Hemorrhoids Hemorrhoids are normal vascular cushions in the anal canal composed of dilated vascular tissue, smooth muscle, and connective tissue. They do not cause issues unless they are enlarged, inflamed, thrombosed, or prolapsed. Patients often present with rectal bleeding of bright red blood, or they may have pain, perianal pruritus, or a palpable mass. Hemorrhoids. Visualization of hemorrhoids Hemorrhoids Hemorrhoids are normal vascular cushions in the anal canal composed of dilated vascular tissue, smooth muscle, and connective tissue. They do not cause issues unless they are enlarged, inflamed, thrombosed, or prolapsed. Patients often present with rectal bleeding of bright red blood, or they may have pain, perianal pruritus, or a palpable mass. Hemorrhoids on exam will provide the diagnosis. Management includes stool softeners, topical hydrocortisone, and sitz baths. Additional treatment options are rubber band ligation and surgical removal.
  • Perianal and perirectal abscess Perirectal Abscess Perianal and perirectal abscesses are collections of pus in the enclosed space near the perirectal tissues. These infections originate from obstruction of anal crypt glands. Patients present with severe pain in the anal or rectal area. Perianal and Perirectal Abscess: collections of pus in the enclosed space near the perirectal tissues: These infections originate from obstruction of anal crypt glands. Patients present with severe pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain in the anal or rectal area. Pruritus is less common. Finding a tender, fluctuant mass on physical exam can provide the diagnosis. Management requires prompt surgical incision and drainage, which may be followed by a course of antibiotics in some cases. 
  • Inflammatory bowel disease (IBD): includes Crohn’s disease and ulcerative colitis Ulcerative colitis Ulcerative colitis (UC) is an idiopathic inflammatory condition that involves the mucosal surface of the colon. It is a type of inflammatory bowel disease (IBD), along with Crohn's disease (CD). The rectum is always involved, and inflammation may extend proximally through the colon. Ulcerative Colitis and is characterized by chronic inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the GI tract due to a cell-mediated immune response to the GI mucosa: Symptoms include diarrhea, abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, weight loss, and extraintestinal manifestations. Diagnosis includes imaging, endoscopy, and biopsy. Treatment involves steroids, aminosalicylates, immunomodulatory, and biologic agents.

References

  1. Ramezani MA, Dehghani MR. (1997). Relationship between Enterobius vermicularis and the incidence of acute appendicitis. Southeast Asian J Trop Med Public Health. https://reference.medscape.com/medline/abstract/17539241
  2. Cho SY, Kang SY. (1975). Significance of scotch-tape anal swab technique in the diagnosis of Enterobius vermicularis infection. Korean J Parasitol. https://www.parasitol.kr/journal/view.php?doi=10.3347/kjp.1975.13.2.102
  3. Bøås H, Tapia G, Sødahl JA, Rasmussen T, Rønningen KS. (2012). Enterobius vermicularis and risk factors in healthy Norwegian children. Pediatr Infect Dis J. https://reference.medscape.com/medline/abstract/22531241
  4. Centers for Disease Control and prevention. Parasitic Diseases Information. Retrieved April 13, 2021, from https://www.cdc.gov/parasites/pinworm/index.html
  5. Rawla P, Sharma S. (2020). Enterobius vermicularis. [online] StatPearls. Retrieved April 13, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK536974/
  6. Pearson RD. (2020). Pinworm infestation. MSD Manual Professional Version. Retrieved April 13, 2021, from https://www.msdmanuals.com/professional/infectious-diseases/nematodes-roundworms/pinworm-infestation
  7. Wolfram W, Afuwape LO, Indra S. (2016). Enterobiasis. In Steele, R.W. (Ed.), Medscape. Retrieved April 13, 2021, from https://emedicine.medscape.com/article/997814-overview
  8. Leder K, Weller PF. (2020). Enterobiasis (pinworm) and trichuriasis (whipworm). In Baron, E.L. (Ed.), UpToDate. Retrieved April 13, 2021, from https://www.uptodate.com/contents/enterobiasis-pinworm-and-trichuriasis-whipworm

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