Trichuris trichiura

Trichuris trichiura

Trichuris trichiura also known as the whipworm is also a soil-transmitted helminth. It gets its name from its characteristic whip-like shapes. Ascaris and Trichuris are frequently observed as occurring together. The helminths causes trichinosis in humans, an intestinal infection. Trichuris is also notable for its small size compared with Ascaris lumbricoides.  T. trichiura was first described by Linnaeus in year 1771.

Habitat
T. trichiura is a common intestinal parasite of man. The adult worm lives in large intestine, primarily in the caecum appendix. It can also be found in the rectum.

Morphology
T. trichiura is relatively smaller in size.   It lacks tissue migration phase in its life cycle.

Adult worm

Adult worms characteristically are whip-shaped, the anterior three-fifth being long, thin and hair-like and posterior one to two fifth being short, thick and stout. Pinkish-white in color. They remain attached to the mucosa woth their entire anterior ends deeply embedded into the mucosa. Worm has an oesophagus and a column of large secretory cells is present in the anterior end of the intestine. Reproductive organs are present in the posterior end of the worm.

Male worm
The male worm measures 30 to 45 mm, slightly shorter than the female. The male has a coiled posterior with a single spicule and retractile sheath.

Female worm
  The female worm is about 35 to 50 mm long and longer than male. The female has a bluntly rounded posterior end. It is oviparous (fertilized eggs lay) and each female has capacity of laying 5000-7000 eggs per day. The adult worm lives for many years in the large intestine.

Eggs

The eggs approximately measures about 50 to 54 μm.   It is barrel shaped with a colourless protruding plug like at each end. These are yellowish brown and double shelled. Outer layer is bile stained. Fertilized eggs are unsegmented at oviposition and embryonic development takes place outside the host. Float in the saturated salt solution. Compared to Ascaris eggs, Trichuris eggs in soil are more susceptible to desiccation. Freshly passed eggs are not infective to humans.

Pathogenesis and pathology

The adult worm invades the intestinal mucosa (caecum and colon) by its thin, thread like anterior end feeds on tissue secretion but not on blood. The anterior portion of the worm, which is embedded in the mucosa, cause petechial hemorrhages, which may predispose to amebic dysentery. The mucosa is hyperemic and edematous; enterorrhagia is common and there may even be rectal prolapse. It also causes occasional eosinophilia. The lumen may be filled with worms, and irritation and inflammation may lead to appendicitis or granulomas (allergic). Approximately, 0.005 ml of blood per worms are lost daily in the infected man.

Clinical manifestation.

The clinical manifestation of T. trichuris infection depend upon the intestinal worm load of the person.

Light trichuris infection
Infection with 100 worms to 200 worms produce light infection. Most infection are asymptomatic.
Heavy trichuris infection
More than 200 worms produce heavy infection. Heavy infection is seen in children and others who eat a lot of dirt. It manifest abdominal discomfort, diarrhea with mucous and blood and retardation of growth. Heavy infection with more than 800 worms produce serious complications. It causes anemia, abdominal pain, nausea, dysenteries and weight loss. Some time causes prolapse of the rectum and causes appendicitis.

Complication.

Rectal prolapse or anemia may occurs in heavely infected children.

Prognosis
Prognosis is excellent. It is rarely fatal.

Epidemiology and distribution.
About 800 million people infected worldwide and common in lesser-developed countries. Commonly found in tropical and subtropical countries with moist and worm soil. The infection is wide spread in tropical Africa, South America and south-East Asia.

Reservoir
Human is the only host. Soil and food contaminated with embryonated eggs are the chief source of infection.

Infection is transmitted by :
Ingestion of embryonated eggs in the contaminated food and water. Contaminated fingers.

Diagnosis

The clinical manifestations are not specific, thus not helpful for diagnosis. Clinical diagnosis is possible only in heavy chronic Trichuris infection.

Laboratory diagnosis.

Laboratory diagnosis is mostly parasitic.

Parasitic diagnosis
Laboratory diagnosis is based on the demonstration of the characteristic barrel-shaped eggs in the feces by light microscopy. Stool concentration methods such as simple salt floatation or formalin ether sedimentation may be required to detect light infection. In heavy infection, adult worm can be also be demonstrate in the rectal mucosa.

Prevention and Control1. Mass treatment may be indicated id infection rates are higher than 50%.
2. Infection in highly endemic areas may be prevented by Treatment of infected individuals.
3. Sanitary disposal of human feces by construction of toilets.
4. Washing of hands with soap and water before meal.
6. Health education on sanitation and personal hygiene.
7. Washing and scalding of uncooked vegetables especially if night soils is used as fertilizers.