Trichuris trichiura - whipworms

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Trichuris trichiura

Taxonomy, Common Name, Disease

 

* CLASS: ADENOPHOREA

* SUBCLASS: ENOPLIA

* ORDER: STICHOSOMIDA (TRICHURATA)

* SUPERFAMILY: TRICHOCEPHALOIDEA

* FAMILY: TRICHURIDAE

 

Scientific name - Trichuris trichiura

 

Common name - whipworm

Hosts

humans

Distribution

Temperate and tropical.

Life Cycle

Estimates of egg production range from 1,000 to 7,000 per day.

Embryonation is completed in about 21 days in soil, which must be

moist and shady. When swallowed, the infective juvenile hatches in the

small intestine and enters the crypts of Lieberkuhn. After a short

period of development, it reenters the intestinal lumen and migrates

to the ileocecal area where it matures in about 3 months. Adults live

for several years, so large numbers may accumulate in a person.

Symptoms-Pathogenicity

Fewer than 100 worms rarely cause clinical symptoms. The majority of

infections are symptomless. The anterior ends of the worms burrow in

the mucosa where the worms consume blood cells, although blood loss by

this mechanism is negligible. Trauma to the intestinal epithelium and

underlying submucosa can cause a chronic hemorrhage that may result in

anemia. Secondary bacterial infections, possibly coupled with allergic

responses, results in colitis, proctitis, and in extreme cases,

prolapse of the rectum. Insomnia, nervousness, loss of appetite,

vomiting, urticaria, prolonged diarrhea, constipation, flatulence, and

verminous intoxication. Symptoms may be confused with those of

hookworm, amebiasis, or acute appendicitis (in some cases the nematode

is found in the appendix).

Management

Mebendazole is the drug of choice. Training of children and adults in

sanitary disposal of feces and washing of hands is necessary to

prevent reinfection.

Importance

In the southeastern U.S. infection may be as high as 20 to 25% mainly

in small children. Worldwide estimate is 355 million people. Probably

the third most common nematode of humans (Ascaris and Enterobius are

number 1 and 2).

Characteristics

Eggs have distinctive bipolar plugs, are 50 to 54 um by 22 to 23 um

and have smooth outer shells. Adults are 30 to 50 mm long, with males

being somewhat smaller than females. The mouth is a simple opening,

lacking lips. The buccal cavity is tiny and is provided with a minute

spear. The esophagus is very long, occupying about two thirds of the

body length and consists of a thin-walled tube surrounded by large,

unicellular glands, the stitchocytes. The entire structure is called a

stichosome. The anterior end of the esophagus is somewhat muscular.

The transition from the anterior filiform portion of the esophagus and

the posterior, stout portion is sudden. Both sexes have a single

gonad, and the anus is near the tip of the tail. Males have a single

spicule that is surrounded by a spiny spicule sheath. The ejaculatory

duct joins the intestine anterior to the cloaca. In the female the

vulva is near the junction of the esophagus and the intestine. The

uterus contains many unembryonated eggs. The excretory system is

absent. The ventral surface of the esophageal region bears a wide band

of minute pores, leading to underlying glandular and nonglandular

cells. This bacillary band is typical of the order.

References

 

1. Schmidt, G.S., and L.S. Roberts. 1989. Chapter 24. Orders

Trichurata and Dioctophymata: Aphasmidian Parasites. in Foundations of

Parasitology. Times Mirror/Mosby College Publishing. St. Louis. 750 pages.

2. Chandler, A.C. and C.P. Read. 1961. Chapter 18. Trichuris,

Trichinella, and Their Allies. Introduction to Parasitology. John

Wiley & Sons, Inc. New York. 822 pages.

3. Cox, F.E.G. 1993. Chapter 2. Parasitic Helminths. in Modern

Parasitology. Blackwell Scientific Publications, UK. 276 pages.

4. Markell, E.K., M. Voge, D.T. John. 1992. Medical Parasitology.

W.B. Saunders Company, Philadelphia. 463 pages.

5. Maggenti, A.R. 1981. General Nematology. Springer-Verlag, New

York. 372 pages.