INTRODUCTION — Enterobius vermicularis (pinworm) and Trichuris trichiura (whipworm) are two of the most common nematode infections worldwide [1].
Enterobiasis occurs in both temperate and tropical climates; it is the most common helminthic infection in the United States and Western Europe. Trichuriasis occurs most commonly in tropical climates.
ENTEROBIASIS (PINWORM) — Enterobiasis occurs in both temperate and tropical climates; it is the most common helminthic infection in the United States and Western Europe [2]. Prevalence estimates suggest there are 40 million infected persons in the United States [3].
Humans are the only natural host. Infection occurs in all socioeconomic groups; transmission is most efficient when people are living in closed, crowded conditions and is common within households. Enterobiasis is observed most frequently among school children aged 5 to 10 years; it is relatively uncommon in children <2 years old.
Life cycle and transmission — E. vermicularis has a simple life cycle (figure 1). The cycle begins with egg deposition by gravid adult female worms on the perianal folds. Autoinfection occurs by scratching the perianal area and transferring infective eggs to the mouth with contaminated hands. Person-to-person transmission can occur by eating food touched by contaminated hands or by handling contaminated clothes or bed linens. Infection may also be acquired via contact with environmental surfaces (curtains, carpeting) that are contaminated with eggs. In addition, eggs may become airborne, inhaled, and swallowed.
Following ingestion, eggs hatch and release larvae in the small intestine. The adult worms establish themselves in the gastrointestinal tract, mainly in the cecum and appendix. The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. Each female worm can produce 10,000 or more eggs. The life span of the adults is two to three months. Most infected individuals have a few to several hundred adult worms. The worm burden is not distributed evenly among individuals; the one-quarter of the population that is most heavily infected has more than 90 percent of the total worm burden [4].
Gravid females migrate through the rectum onto the perianal skin to deposit eggs; this usually occurs at night. The larvae inside the eggs generally mature within four to six hours, resulting in infective eggs. The eggs begin to lose infectivity after one to two days under warm and dry conditions but may survive more than two weeks in cooler, more humid environments.
Clinical manifestations — Most Enterobius infections are asymptomatic. The most common symptom of enterobiasis is perianal itching, also known as pruritus ani. This is caused by an inflammatory reaction to the presence of adult worms and eggs on the perianal skin and occurs predominantly at night. Scratching leads to lodging of eggs beneath the fingernails, facilitating subsequent autoinfection and/or person-to-person transmission. Secondary bacterial infections can result if the excoriation is severe. Nocturnal pruritus can also lead to difficulty sleeping [5].
Occasionally, the worm burden is so high that abdominal pain, nausea, and vomiting develop. Adult pinworms may be found in normal and inflamed appendices following surgical removal, but whether or not they cause appendicitis is still debated [6-12]. Eosinophilic enterocolitis can occur, though peripheral eosinophilia is generally not observed [13,14]. (See "Eosinophilic gastrointestinal diseases".)
In addition, adult worms can migrate to extraintestinal sites. Vaginal enterobiasis can occur with a wide range of clinical presentations; many patients are asymptomatic, but vulvovaginitis has been described, which can increase susceptibility to urinary tract infections [15-17]. Involvement of other genitourinary sites has been described including salpingitis, oophoritis, cervical granuloma, and peritoneal inflammation. Enterobius infestation of the nasal mucosa has also been observed [18].
Diagnosis — Enterobiasis should be suspected in patients with anal pruritus, particularly school-aged children.
The diagnosis can be established in one of the following ways:
●Visual inspection of the anal verge and undergarments, where mobile worms are sometimes visible. The white, pin-shaped female pinworm (8 to 13 mm long) may look like bits of cotton thread and can be confirmed by laboratory identification (picture 1).
●Paddle test – The paddle test is performed by pressing a plastic paddle (coated with an adhesive surface) or piece of cellophane tape against the perianal region and then placing onto a glass slide, which is then examined under a microscope for pinworm eggs. The diagnostic yield is greatest if the test is performed at night or first thing in the morning prior to bathing. Repeat testing over three days may be necessary to increase the sensitivity.
●Samples collected from under fingernails may be analyzed for pinworm eggs.
Eggs are 50 by 25 micron and are asymmetrically flattened on one side, giving a characteristic "bean-shaped" appearance (picture 2).
Stool examination is not useful since worms and eggs are generally not passed in stool.
Differential diagnosis — The differential diagnosis includes of enterobiasis includes infectious, dermatologic, and other causes. (See "Approach to the patient with anal pruritus".)
Treatment — The approach to treatment of enterobiasis is discussed below. In the absence of definitive diagnosis, empiric treatment is reasonable for patients with relevant clinical manifestations of anal pruritus. In cases of confirmed enterobiasis, simultaneous treatment of the entire household is warranted regardless of symptoms in other household members given high transmission rates within households.
Nonpregnant adults and children — Options for treatment of enterobiasis include [19-22]:
●Albendazole (adults and children: 400 mg orally once on empty stomach, repeat in two weeks)
●Mebendazole (adults and children: 100 mg orally once, repeat in two weeks)
●Pyrantel pamoate (adults and children: 11 mg/kg, maximum 1 g; repeat in two weeks; available over the counter in the United States)
The above regimens have been associated with cure rates of 90 to 100 percent in a number of studies [8,22,23].
Ivermectin has efficacy against E. vermicularis but is not generally used for this indication [24-26]. Piperazine is not used because of lower efficacy and higher toxicity compared with the benzimidazoles.
Pregnant women — Treatment of enterobiasis in pregnant women should be reserved for patients with significant symptoms. Pyrantel pamoate is favored over mebendazole or albendazole for treatment of symptomatic enterobiasis in pregnant women [27,28]. The dosing is the same as for nonpregnant adults. (See 'Nonpregnant adults and children' above.)
In one study of 192 pregnant women exposed to mebendazole during pregnancy (72 percent during the first trimester), no increase in major malformations was observed compared with matched controls, although there were more elective terminations in the group receiving mebendazole [29].
Preventing transmission — In addition to treatment, all bedding and clothes should be washed. Hygienic measures, such as clipping of fingernails and frequent handwashing are also helpful for reducing reinfection and spread of infection. Showering is preferred over taking a bath, because showering avoids potential contamination of bath water with pinworm eggs [30].
TRICHURIASIS (WHIPWORM) — Trichuriasis occurs most commonly in tropical climates. It is estimated that approximately one-quarter of the world population carries this parasite [31]. In communities where trichuriasis is endemic, infection may be present in more than 90 percent of individuals, but the majority of the total worm burden is generally carried by fewer than 10 percent [32]. T. trichiura is frequently observed in association with other geohelminths such as Ascaris lumbricoides, since these pathogens thrive under similar conditions. (See "Ascariasis".)
Transmission of trichuriasis is associated with poor hygiene. Individuals of all ages can become infected. Children are particularly vulnerable to infection because of their high exposure risk and because partial protective immunity is thought to develop with age.
Life cycle and transmission — The life cycle for trichuriasis begins with passage of unembryonated eggs in the stool (figure 2). In the soil, the eggs embryonate and become infective in 15 to 30 days. After ingestion via food or hands contaminated with soil, the eggs hatch in the small intestine and release larvae that mature into adult worms, which become established in the cecum and ascending colon after two to three months. In heavy infections, worms may also be found in the distal colon and rectum [31].
The adults measure approximately 4 cm in length. The thin end is embedded in the bowel mucosa and the thick end is visible within the bowel lumen. The females begin to produce eggs 60 to 70 days after infection and shed 3000 to 20,000 eggs per day. The life span of the adults is one to three years.
Reinfection is common following therapy in endemic areas. Adequate disposal of human feces and good sanitary conditions can interrupt transmission. Good personal hygiene and careful washing of vegetables and fruits grown in contaminated areas is also important.
Clinical manifestations — Most infections with T. trichiura are asymptomatic. Clinical symptoms are more frequent with moderate to heavy infections. Stools can be loose and often contain mucus and/or blood. Nocturnal stooling is common. Colitis and dysentery occur most frequently among individuals with >200 worms, and secondary anemia may be observed. Infected individuals may have a peripheral eosinophilia of up to 15 percent.
Rectal prolapse can occur in the setting of heavy infection, and embedded worms may be visualized directly in the mucosa of the inflamed rectum (picture 3). Pica and finger clubbing are other potential clues to the diagnosis.
Children who are heavily infected may have impaired growth and/or cognition [33,34]. However, it can be difficult to quantify the role of trichuriasis in isolation from comorbidities and other social factors.
Diagnosis — The diagnosis of trichuriasis is established via stool examination for eggs (picture 4). The eggs are 50 by 20 microns and have a characteristic barrel shape with smooth thick wall and a hyaline plug at each end. The Kato-Katz technique can be used to quantify egg numbers, which tends to correlate with the adult worm burden [35,36]. Particularly in light infections, examination of more than one sample improves sensitivity, and three samples should optimally be examined before excluding infection.
Polymerase chain reaction (PCR) using next-generation sequencing techniques are increasingly becoming available and are able to detect soil-transmitted helminths including T. trichiura. The utilization of such methodologies has the ability to improve species specificity and limits of parasite detection [37]. Sensitivity and specificity vary according the specific test used. In one study evaluating a multiplex PCR, the sensitivity and specificity were 87 and 83 percent, respectively , compared with stool microscopy [38]. In another study (using the combined results of triplicate Kato-Katz thick smears and PCR as the gold standard), the sensitivity of quantitative PCR for detecting T. trichiura was 72 percent [39]. PCR tests may therefore become an increasingly more standard method for diagnosing or ruling out infection.
If proctoscopy or colonoscopy are performed, adult worms protruding from the bowel mucosa may be observed (picture 5). The adult worm is shaped like a whip; the posterior part of the worm is relatively wide and looks like a whip handle, and the anterior part is long and thin.
Treatment
Nonpregnant adults and children — For patients with trichuriasis, we treat asymptomatic and symptomatic cases.
●Treatment regimens – Treatment regimen options include [19,40,41]:
•Monotherapy with either albendazole (adults and children: 400 mg orally once daily for three days) or mebendazole (adults and children: 100 mg orally twice daily for three days)
•Combination therapy with albendazole (400 mg orally once daily for three days) plus ivermectin (600 mcg/kg once daily for three days)
We prefer initial treatment with either albendazole or mebendazole (three-day regimen). Combination therapy (ivermectin plus albendazole) is a reasonable alternative treatment and appeared to have superior efficacy in one trial; a three-day course of albendazole and ivermectin had a slightly higher egg reduction rate (100 versus 98 percent) and cure rate (100 versus 89 percent) than a single-day course of combination therapy [41]. Single-dose albendazole or mebendazole has insufficient efficacy and should not be used.
●Alternative regimens – Proposed alternative regimens include combination therapy with oxantel pamoate and albendazole (for two days) or combination therapy with oxantel pamoate and ivermectin (either alone or in combination with other anthelminthic agents) [42]; further study of these regimens is needed, and these regimens are therefore not recommended as first-line therapy.
●Follow-up – We perform follow-up stool examination a few weeks after treatment to detect those with persistent infection; this is especially important for patients with heavy infections (at least 1000 Trichuris eggs/g stool). In patients with heavy infection, treatment with albendazole for a longer duration (five to seven days) may be warranted [19,43-45].
●Efficacy
•Combination therapy – Use of combination therapy is supported by the following trials:
-In a 2019 meta-analysis including 114 studies, one-day combination therapy with albendazole-ivermectin was more efficacious than one-day albendazole monotherapy for curing T. trichiura infection (relative risk 3.22, 95% CI 1.84-5.63) [46].
-In a 2021 randomized trial including 176 children with trichuriasis in Honduras, three-day combination therapy (albendazole 400 mg and ivermectin 200 mcg/kg) was associated with a slightly higher egg reduction rate (100 versus 98 percent) and cure rate (100 versus 89 percent) than one-day combination therapy [41].
-In a 2022 randomized trial including more than 1600 patients age 6 to 60 years with trichuriasis among three study sites, higher cure rates were observed among those treated with one-day combination therapy (albendazole 400 mg and ivermectin 200 mcg/kg) than among those treated with one-day monotherapy (albendazole 400 mg) in Laos (66 versus 8 percent) and Pemba Island (49 versus 6 percent), but not in Côte d’Ivoire (14 versus 10 percent) [47].
•Monotherapy – In general, the efficacy of monotherapy for treatment of trichuriasis is relatively low, especially when administered as a single dose. In one trial including 240 children in Tanzania with trichuriasis randomly assigned to treatment with mebendazole (500 mg single dose) or albendazole (400 mg single dose), cure rates and egg reduction rates 21 days later were higher among those treated with mebendazole (11.8 versus 2.6 percent and 75 versus 45 percent, respectively) [42]. In a subsequent meta-analysis including 38 trials and more than 8800 patients with trichuriasis, cure rates for mebendazole and albendazole were 42 and 31 percent, respectively [40].
Data on use of ivermectin monotherapy for treatment of trichuriasis are limited [24,25,48]. In one study including 126 preschool-aged children in Côte d'Ivoire with trichuriasis, ivermectin (200 mcg/kg orally once) was no more effective than placebo; among 166 school-aged children, the cure rate of ivermectin (up to 600 mcg/kg) was only 12 percent [49].
Data on use of oxantel pamoate (monotherapy) for treatment of trichuriasis are limited, and drug availability is limited [42,50]. In one study including 350 children in Tanzania with trichuriasis randomly assigned to treatment with oxantel pamoate or placebo, the optimum therapeutic dose range was 15 to 30 mg/kg (15 mg/kg: 49 percent cure and 97 percent egg reduction rate; 30 mg/kg: 59 percent cure rate and 99 percent egg reduction rate) [41,50].
●Mass treatment – In regions where mass chemotherapy is given without follow-up of individuals for detection of cure, use of oxantel pamoate in combination with albendazole may be more efficacious than mebendazole or albendazole alone [42,51]. In the above trial of children with trichuriasis in Tanzania, 119 were randomly assigned to treatment with this regimen (oxantel pamoate 20 mg/kg, plus 400 mg of albendazole, administered on consecutive days); three weeks later, the cure rate was 31 percent and the egg reduction rate was 96 percent [42].
Issues related to population-based treatment are discussed separately. (See "Mass drug administration for control of parasitic infections".)
Pregnant women — Mebendazole and albendazole should be avoided during pregnancy, particularly during the first trimester. The risks of administering treatment to pregnant women with trichuriasis must be weighed against the risks of delaying treatment. Therapy for patients with trichuriasis in the absence of significant symptoms can be deferred until after delivery.
Differential diagnosis — The differential diagnosis includes of trichuriasis depends on the presentation.
●For patients with symptomatic intestinal infection, other relevant nematodes (roundworms) include Ascaris, hookworm (Ancylostoma duodenale and Necator americanus), and Strongyloides. Loose stools or colitis may be caused by a range of infectious agents that can be identified via stool examination including bacteria (Salmonella, Campylobacter, Shigella, enterotoxigenic Escherichia coli, Yersinia, and others), viruses (norovirus, rotavirus, adenoviruses, astrovirus, and others), protozoa (Cryptosporidium, Giardia, Cyclospora, Entamoeba, and others), or by noninfectious etiologies including inflammatory bowel disease. (See "Diagnostic approach to diarrhea in children in resource-rich countries" and "Approach to the adult with acute diarrhea in resource-rich settings".)
●Eosinophilia has a range of infectious (especially other helminths) and noninfectious causes. (See "Approach to the patient with unexplained eosinophilia".)
●Rectal prolapse may be caused by A. lumbricoides or other infections, conditions that increase intra-abdominal pressure, cystic fibrosis, pelvic floor weakness, and other conditions. (See "Overview of rectal procidentia (rectal prolapse)" and "Rectal prolapse in children".)
MEDICATION COST — The cost of albendazole and mebendazole in the United States can be prohibitive for patients without adequate prescription drug coverage. According to a website that compares retail drug prices without insurance (GoodRx), generic albendazole costs $200 to 300 USD per course; mebendazole (brand Emverm) $1000 to 1500 USD per course [52]. Pyrantel pamoate treatment is available without a prescription at about $20 USD per course. Resources for patients needing help with prescription costs are available. (See 'Information for patients' below.)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Pinworms (The Basics)" and "Patient education: Coping with high drug prices (The Basics)")
●Beyond the Basics topic (see "Patient education: Coping with high prescription drug prices in the United States (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Epidemiology − Enterobius vermicularis (pinworm) and Trichuris trichiura (whipworm) are two of the most common nematode infections worldwide. Enterobiasis occurs in both temperate and tropical climates; it is the most common helminthic infection in the United States and Western Europe. Trichuriasis occurs most commonly in tropical climates. (See 'Introduction' above.)
●Enterobiasis (pinworm)
•Life cycle − The life cycle of Enterobius begins with egg deposition by gravid adult female worms on the perianal folds (figure 1). Autoinfection occurs by scratching the perianal area and transferring infective eggs to the mouth with contaminated hands. Person-to-person transmission can occur by eating food touched by contaminated hands or by handling contaminated clothes or bed linens. (See 'Life cycle and transmission' above.)
•Clinical manifestations and diagnosis − Most Enterobius infections are asymptomatic. The most common symptom of enterobiasis is perianal itching, which occurs predominantly at night. Occasionally, the worm burden is so high that abdominal pain, nausea, and vomiting develop. Enterobiasis can be diagnosed via egg examination of cellophane tape or plastic paddle (coated with an adhesive surface) after pressing to the perianal skin (picture 2). The utility of stool examination is limited since worms and eggs are not generally passed in stool. (See 'Clinical manifestations' above and 'Diagnosis' above.)
•Treatment − For patients with enterobiasis, we suggest treatment with albendazole, mebendazole, or pyrantel pamoate (Grade 2C); dosing is outlined above. Simultaneous treatment of the entire household is warranted, given high transmission rates within households. (See 'Treatment' above.)
●Trichuriasis (whipworm)
•Life cycle − The life cycle for trichuriasis begins with passage of unembryonated eggs in the stool, which become infective in 15 to 30 days (figure 2). After ingestion via food or hands contaminated with soil, the eggs hatch and release larvae that mature into adults worms that become established in the colon after two to three months. (See 'Life cycle and transmission' above.)
•Clinical manifestations and diagnosis − Most trichuriasis infections are asymptomatic. Rectal prolapse can occur, primarily in the setting of heavy infection. Stools can be loose and often contain mucus and/or blood. Nocturnal stooling is common. The diagnosis of trichuriasis is made by stool examination for eggs (picture 4). (See 'Clinical manifestations' above and 'Diagnosis' above.)
•Treatment − For patients with trichuriasis, we suggest initial treatment with either albendazole or mebendazole (three-day regimen) (Grade 2C). Combination therapy (ivermectin plus albendazole) is a reasonable alternative. Single-dose albendazole or mebendazole has insufficient efficacy and should not be used. Dosing is summarized above. (See 'Treatment' above.)
