Trichuris trichiura, also known as the human whipworm, is a roundworm that causes trichuriasis in humans. It is referred to as the whipworm because it looks like a whip with wide handles at the posterior end. The whipworm has a narrow anterior esophagus and a thick posterior anus. The worms are usually pink and attach to the host via the slender anterior end. The size of these worms varies from 3 to 5 cm. The female usually larger than the male.
The female worm can lay anywhere from 2000 to 10,000 eggs per day. The eggs are deposited in soil from human feces. After 14 to 21 days, the eggs mature and enter an infective stage. If humans ingest the embryonated eggs, the eggs start to hatch in the human small intestine and utilize the intestinal microflora and nutrients to multiply and grow. The majority of larvae move to the cecum, penetrate the mucosa and mature to adulthood. Infections involving a high-worm burden will typically involve distal parts of the large intestine.
Trichuriasis is 1 of 3 well-documented soil-transmitted helminthiasis infections; the other 2 are ascariasis and hookworm infection. It is considered a neglected tropical disease by the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC).
The most common cause of trichuriasis is ingestion of infected eggs that are found in soil. This is often due to poor sanitary conditions, including open defecation and using human feces as fertilizer.
Some recent studies show that people with certain chromosome traits may be predisposed or have increased susceptibility to acquiring trichuriasis.
The egg of the whipworm is the infective stage, and favorable conditions for its maturation are warm and humid climate. This is why most of the disease burden is seen in tropical climates, specifically in Asia and less often, in Africa and South America. It is also found in rural parts of the southeast United States.
It is estimated that worldwide there are between 450 million to 1 billion active cases with most diagnosed in children. It is thought there is partial protective immunity that develops with age.
A human host consumes infected eggs, typically while eating food. Once the embryonated eggs are ingested, the larvae hatch in the small intestine. From there they migrate to the large intestine, where the anterior ends lodge within the mucosa. This leads to cell destruction and activation of the host immune system, recruiting eosinophils, lymphocytes and plasma cells. This causes the typical symptoms of rectal bleeding and abdominal pain.
Patients will typically reside in or have visited areas that are endemic to the whipworm. The patient will usually complain of abdominal pain, painful passage of stools, abdominal discomfort, and mucus discharge. Rectal prolapse is known to occur in a heavy infestation. Children may develop anemia, growth retardation, and even impaired cognitive development. The latter 2 are thought to be due to iron deficiency and poor nutrition secondary to worm burden and are not a direct cause of the infestation.
The diagnosis is made by using the Kato-Katz method for counting eggs per unit weight of feces. One caveat is that from the time the eggs are ingested to development of the mature worm, there is a time lag of about three months. During this period, there may be no signs of an infestation and the stools may not show evidence of any eggs or shedding.
There have been case reports of patients reporting symptoms in areas that are resource-rich where the diagnosis has been made with colonoscopy. The classic finding is the “coconut cake rectum.” There have recently been studies which show a whipworm dance on ultrasound, and this is a modality that can easily be used in resource-poor settings.
PCR assays are currently being developed and used. This has improved the specificity and sensitivity of detecting the whipworm.
The treatment is with mebendazole or albendazole. The suggested dose of mebendazole 100 mg twice a day for 3 days or albendazole is 200 to 400 mg twice a day for 3 days. Mebendazole has been shown to be more effective and is considered the first-line treatment.
Ivermectin (200 mcg/kg daily) can be used; however, it is not as effective as the first 2.
It is important to keep in mind that there are often co-infections with other helminths so treatments with multiple medications may be required.
Given that a whipworm infection can cause abdominal pain, there includes a large differential of abdominal processes. These include but are not limited to appendicitis, colitis, cholecystitis, perforated intestine. Bloody diarrhea can be caused by inflammatory bowel disease (IBD), bacterial pathogens or other soil-transmitted helminths. The constellation of cognitive disruption, constipation, and abdominal pain can also be seen with lead toxicity and is an important consideration for children.
The differential should include:
The whipworm tends to be more resistant to treatment than other helminths, with some studies listing cure rates as low as 28% to 36%. Whipworms can still be present after treatment however it is thought that a low worm count leads to no significant disease burden.
Trichuris dysentery syndrome can be found in children (with no adult cases noted) and is seen when there is a very high worm burden. This often leads to diarrhea, tenesmus, iron deficiency anemia and growth retardation. The growth retardation is typically secondary to poor nutrition and consequently causes the cognitive delay.
Adults and children should be treated appropriately for the anemia they experience. Many global organizations stress the importance of increased education for children who have been treated for whipworm infection. Not doing so keeps them behind in school when compared to peers of their same age group who were not infected.
The best way to prevent trichuriasis is to improve personal hygiene, wash all fruit and vegetables, and teach everyone about the importance of hand washing. Global initiatives have been started which focus on improved sanitation, poverty reduction, and periodic chemotherapy.
The diagnosis of whipworm is not easy because the infection is not often encountered in the US. The disorder is best managed by a multidisciplinary team that includes an infectious disease expert, internist, gastroenterologist, and the primary care physician. Following treatment, education of the patient is vital to prevent recurrence.
The infectious disease nurse should emphasize the need to improve personal hygiene, wash all fruit and vegetables, and teach everyone about the importance of hand washing. Global initiatives have been started which focus on improved sanitation, poverty reduction, and periodic chemotherapy.
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