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Trichuris trichiura - Introduction, Classification, History, Habitat, Morphology, Life Cycle

Last Modified: March 11, 2023

Introduction to Trichuris trichiura

Trichuris trichiura, commonly known as whipworm, is a helminth parasite that causes trichinosis in humans. This intestinal infection occurs due to the invasion of the mucosa of the colon by the adult parasite.

The name whipworm is derived from its characteristic ship-like shape i.e. it resembles a whip with wider “handles” at its posterior end.

The parasitic roundworm is scientifically also known as Trichocephalus trichiurus.

History of Trichuris trichiura

Historically, Trichuris trichiura was first described in 1771 by Linnaeus.

Habitat of Trichuris trichiura

Trichuris trichiura is a common intestinal parasite in humans. The adult worm inhabits the large intestine, primarily in the caecum and the appendix and less commonly in the host rectum.

Morphology of Trichuris trichiura

The morphological feature of Trichuris trichiura is its relatively smaller size and the lack of tissue migration phase in its life cycle.

The parasite’s morphological stages include – adult (male, female), and eggs.

Figure: adult female (a) and male (b) Trichuris trichiura (Source: Jotscroll)

Adult worm

  • adult worm of Trichuris trichiura is whip-shaped

  • pinkish-white in color

  • three-fifth part of the anterior end is long, thin and hair-like

  • posterior one-to-two fifth part is short, thick, and stout

  • whipworm remains attached to the intestinal mucosa with the help of their anterior end

  • the anterior end is deeply embedded into the mucosa

  • presence of an esophagus

  • the anterior end of the intestine has a column of large secretory cells

  • the posterior end has reproductive organs

Male

  • male Trichuris trichiura measures 30 mm to 40 mm in length

  • recognized by characteristic coiled posterior end

Female

  • female Trichuris trichiura measures 40 mm to 50 mm in length i.e. longer than make

  • blunt posterior end

  • oviparous

  • each female lays 5000-7000 eggs in a day

  • has a life-span of many years

Figure: Trichuris trichiura egg (Source: Slide Share)

Egg

  • Trichuris trichiura eggs are barrel-shaped

  • measures 50 μm to 54 μm in length and 22 μm to 23 μm in breadth

  • has a colorless protruding mucus plug at each end

  • yellowish brown with a double shell

  • the outer shell is bile-stained while the inner shell is not

  • floats in saturated salt solution

  • when passed in the host feces, eggs contain an unsegmented ovum each

  • the freshly passed stool is not infective to humans

Life Cycle of Trichuris trichiura

The life cycle of Trichuris trichiura is simple i.e. it is completed in a single host. Unlike Ascaris and hookworm, this parasite has no tissue migratory phase. However, for its life cycle to be complete, a change of host is necessary.

  • Humans acquire Trichuris trichiura infection after ingesting soil containing embryonated eggs

  • these embryonated eggs hatch in the intestine to release larvae

  • the larvae penetrate the villi where they continue to develop

  • after 7 days, these young Trichuris trichiura leave the small intestine and reaches the caecum where they sexually mature into male and female adults

  • following fertilization, the female adult begins laying fertilized eggs

    * the time between infection by Trichuris trichiura and laying eggs is about 3 months

  • these unembryonated eggs are excreted out with the host's feces

  • each adult female can lay about 5,000 to 7,000 eggs per day for around 5 years

  • after the eggs present in the host feces reaches damp warm soil, further development of eggs takes place

  • within 10 to 14 days, these eggs develop into embryonated eggs – each containing a rhabditiform larva

    * Only such embryonated eggs are infectious to humans while freshly laid unembryonated eggs cannot cause infection

  • in moist soil, the embryonated eggs can remain viable/infective for several months

  • if these embryonated eggs are consumed by other human hosts, transmission occurs and the life cycle of Trichuris trichiura is completed

Figure: Trichuris trichiura life-cycle (Source: CDC)

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