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

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

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

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

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

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: Atypical egg of T. trichiura.

Figure B: Atypical egg of T. trichiura.

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

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

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

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

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

Treatment information for trichuriasis can be found at: https://www.cdc.gov/parasites/whipworm/health_professionals/index.html

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: December 19, 2017
  • Page last updated: December 19, 2017
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