Friday, 11 June 2010

Whipworm (Trichuris trichiura)

Helminth – Nematode - (Roundworm)

Trichuris trichiura (Whipworm) infections are most common in warm, moist areas of the world and are often seen in conjunction with Ascaris infections. Infections can be asymptomatic or symptomatic depending on the worm burden.
People exhibiting clinical symptoms may have abdominal pain, diarrhea, anemia and weight loss. Severe cases may result in rectal prolapses. Mechanical damage to the mucosal surface and allergic response by the patient appear to be the cause illness.

Worm Morphology;
Whipworms were named for their overall appearance – a narrow anterior with a thicker posterior giving the appearance of a handle with whip attached.
Whipworms measure from about 35 to 50 mm long with the male measuring somewhat shorter (30 to 45 mm), the male having a coiled tail.
The whipworm actually attaches itself into the lining of the cecum using hooklets at it's anterior (thin) end.

Life Cycle;
Unlike many roundworms, there is no circulation of the whipworm's larval stages throughout the body but is rather confined to the intestinal tract.
Human infection is acquired through the ingestion of fully embryonated eggs found in the environment. The eggs hatch in the small intestine and eventually attach to the mucosa of the large intestine. Adults mature in about 3 months and then begin egg production.
The eggs are passed in the feces in an infertile state and require about 10 to 14 days outside of the body, in a moist soil environment to embryonate and become infective.

Egg Morphology;
Trichuris trichiura eggs are 'football' or 'barrel' shaped with clear, mucoid-appearing polar plugs at each end. They are about 50 to 54 µm by about 22 to 23 µm wide.

Definitive laboratory diagnosis is made by demonstrating Trichuris trichiura eggs in the patient's stool. Eggs are best seen in stool concentrates but can also be seen in permanent stained smears. Stools preserved in PVA (polyvinyl alcohol) do not concentrate as well as those preserved in formalin and light infections may be missed. Adult worms are very rarely seen in stool samples.

Abendazole, although not as effective in treating whipworm as it is with other intestinal nematodes, it remains the drug of choice.

The geographic range of T. trichiura is similar to that of A. Lumbricoides and often the two infections are found together.
Infections are found most often in children as the eggs often are found contaminating the soil where they play.
Appropriate sanitation and disposal of feces helps break the reinfection cycle.

Whipworm segment in Histological Section

Another Section at Higher Magnification
(Note Trichuris Eggs Within Lumen of Worm)

Barrel or Football Shaped Egg (Fecal Concentrate)
(Note Polar Plugs -at each end)

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