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Trichuriasis

[Trichuris trichiura]

Causal Agent

The nematode (roundworm) Trichuris trichiura, also called the human whipworm.


Life Cycle

lifecycle

The unembryonated eggs are passed with the stool The number 1. In the soil, the eggs develop into a 2-cell stage The number 2, an advanced cleavage stage The number 3, and then they embryonate The number 4; eggs become infective in 15 to 30 days. After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae The number 5 that mature and establish themselves as adults in the colon The number 6. The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. The adult worms are fixed in that location, with the anterior portions threaded into the mucosa. The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year.

Geographic Distribution

The third most common round worm of humans. Worldwide, with infections more frequent in areas with tropical weather and poor sanitation practices, and among children. It is estimated that 800 million people are infected worldwide. Trichuriasis occurs in the southern United States.

Clinical Presentation

Most frequently asymptomatic. Heavy infections, especially in small children, can cause gastrointestinal problems (abdominal pain, diarrhea, rectal prolapse) and possibly growth retardation.

T. trichiura eggs.

 

Trichuris trichiura eggs are 50-55 micrometers by 20-25 micrometers. They are barrel-shaped, thick-shelled and possess a pair of polar “plugs” at each end. The eggs are unembryonated when passed in stool.
	Figure A

Figure A: Egg of T. trichiura in an iodine-stained wet mount.

	Figure B

Figure B: Egg of T. trichiura in an unstained wet mount.

	Figure C

Figure C: Egg of T. trichiura in an unstained wet mount.

	Figure D

Figure D: Eggs of T. trichiura in a wet mount, showing variability in size in the species.

	Figure E

Figure E: Egg of T. trichiura viewed with UV microscopy.

	Figure F

Figure F: Egg of T. trichiura in an unstained wet mount of stool. Notice also the presence of a cyst of Entamoeba coli (arrow).

Atypical T. trichiura eggs.

	Figure A

Figure A: Atypical egg of T. trichiura.

	Figure B

Figure B: Atypical egg of T. trichiura.

	Figure C

Figure C: Atypical egg of T. trichiura.

Cross-sections of T. trichiura stained with hematoxylin and eosin (H&E).

 

Cross sections of Trichuris trichiura stained with hematoxylin and eosin (H&E).
	Figure A

Figure A: Cross-section of a gravid female T. trichiura stained with Hamp;E, showing numerous eggs. Magnification at 100x. Image courtesy of the Oregon State Public Heath Laboratory.

	Figure B

Figure B: Same specimen as in Figure A but at 1000x magnification, showing a close-up of one of the eggs.

	Figure C

Figure C: Cross-section of the posterior end of an adult T. trichiura, from a colonoscopy specimen stained with Hamp;E. Note the presence of the thick cuticle with annulations (CU). Below the cuticle is the thin hypodermis (HY), and below the hypodermis is a layer of somatic muscle cells (SO). The presence of a spicule (SP) indicates the specimen is a male. Image courtesy of the Michael E. DeBakey V. A. Medical Center, Houston, TX.

	Figure D

Figure D: Section of an adult T. trichiura, stained with H&E. Notice the thick-muscled cloaca (arrow). Image courtesy of Cambridge Health Alliance, Cambridge, MA.

	Figure E

Figure E: Another image from the specimen in Figure D. Notice the thick cuticle with annulations (CU), a thin nucleate hypodermis (HY) and layers of polymyarian muscle cells (PO).

	Figure F

Figure F: Cross-section of the anterior end of the specimen in Figures D and E. Notice the bacillary band (BB), a stichocyte (ST) and stichosome nucleus (SN).

T. trichiura adults.

 

Adult males of Trichuris trichiura are 30-45 millimeters long, with a coiled posterior end. Adult females are 35-50 millimeters with a straight posterior end. Both sexes have a long, whip-like anterior end. Adults reside in the large intestine, cecum and appendix of the host.
	Figure A

Figure A: Posterior end of an adult T. trichiura, taken during a colonoscopy. Image courtesy of Duke University Medical Center.

	Figure B

Figure B: Adult if T. trichiura removed during a colonoscopy.

	Figure C

Figure C: Higher magnification of the anterior end of the specimen in Figure B.

	Figure D

Figure D: Higher magnification of the posterior end of the specimen in Figure B. Notice the prominent spicule.

Laboratory Diagnosis

Microscopic identification of whipworm eggs in feces is evidence of infection. Because eggs may be difficult to find in light infections, a concentration procedure is recommended. Because the severity of symptoms depend on the worm burden, quantification of the latter (e.g. with the Kato-Katz technique) can prove useful.

Examination of the rectal mucosa by proctoscopy (or directly in case of prolapses) can occasionally demonstrate adult worms.

Morphologic comparison with other intestinal parasites

Treatment Information

Whipworm is effectively treated with albendazole, mebendazole or ivermectin. Each drug needs to be taken for 3 days. Dosage guidelines are the same for children as for adults. Albendazole should be taken with food. Ivermectin should be taken with water on an empty stomach and the safety of ivermectin for children weighing less than 15 kg has not been established. Neither albendazole nor ivermectin is FDA-approved for treating whipworm.

Drug Dosage for adults and children
Albendazole 400 mg orally for 3 days
Mebendazole 100 mg orally twice a day for 3 days
Ivermectin 200 mcg/kg/day orally for 3 days

Albendazole

Oral albendazole is available for human use in the United States.

Albendazole is pregnancy category C. Data on the use of albendazole in pregnant women are limited, though the available evidence suggests no difference in congenital abnormalities in the children of women who were accidentally treated with albendazole during mass prevention campaigns compared with those who were not. In mass prevention campaigns for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of albendazole in the 2nd and 3rd trimesters of pregnancy. However, the risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

It is not known whether albendazole is excreted in human milk. Albendazole should be used with caution in breastfeeding women.

The safety of albendazole in children less than 6 years old is not certain. Studies of the use of albendazole in children as young as one year old suggest that its use is safe. According to WHO guidelines for mass prevention campaigns, albendazole can be used in children as young as 1 year old. Many children less than 6 years old have been treated in these campaigns with albendazole, albeit at a reduced dose.

Mebendazole

Mebendazole is available in the United States only through compounding pharmacies.

Mebendazole is in pregnancy category C. Data on the use of mebendazole in pregnant women are limited. The available evidence suggests no difference in congenital anomalies in the children of women who were treated with mebendazole during mass treatment programs compared with those who were not. In mass treatment programs for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of mebendazole in the 2nd and 3rd trimesters of pregnancy. The risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

It is not known whether mebendazole is excreted in breast milk. The WHO classifies mebendazole as compatible with breastfeeding and allows the use of mebendazole in lactating women.

The safety of mebendazole in children has not been established. There is limited data in children age 2 years and younger. Mebendazole is listed as an intestinal antihelminthic medicine on the WHO Model List of Essential Medicines for Children, intended for the use of children up to 12 years of age.

Ivermectin

Oral ivermectin is available for human use in the United States.

Ivermectin is pregnancy category C. Data on the use of ivermectin in pregnant women are limited, though the available evidence suggests no difference in congenital abnormalities in the children of women who were accidentally treated during mass prevention campaigns with ivermectin compared with those who were not. The World Health Organization (WHO) excludes pregnant women from mass prevention campaigns that use ivermectin. However, the risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

Ivermectin is excreted in low concentrations in human milk. Ivermectin should be used in breast-feeding women only when the risk to the infant is outweighed by the risk of disease progress in the mother in the absence of treatment.

The safety of ivermectin in children who weigh less than 15kg has not been demonstrated. According to the WHO guidelines for mass prevention campaigns, children who are at least 90 cm tall can be treated safely with ivermectin. The WHO growth standard curves show that this height is reached by 50% of boys by the time they are 28 months old and by 50% of girls by the time they are 30 months old, many children less than 3 years old been safely treated with ivermectin in mass prevention campaigns, albeit at a reduced dose.

 

 

DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/.

  • Page last reviewed: May 3, 2016
  • Page last updated: May 3, 2016
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