Trichuris trichiura (Pathogen – Intestinal Nematode)
Trichuris trichiura (Pathogen – Intestinal Nematode)
Trichuris trichiura (whipworm) belongs to the nematodes, is a pathogen, and causes disease. These nematodes are much larger than the pinworms, measuring 35 to 50 mm long (female) and 30 to 45 mm long (male); the male has a 360° coil at the caudal extremity. The adult worms are rarely recovered from the stool, since they are attached to the wall of the intestine.
|Adult male and female Trichuris
Note: clear polar plugs at both ends of the eggs
|Adult Trichuris worms
|Rectal prolapse in child
Human infection is acquired through ingestion of the fully embryonated eggs from the soil. The eggs hatch in the small intestine and eventually attach to the mucosa in the large intestine. The adults mature in about 3 months and begin egg production.
Infection in humans is acquired through ingestion of the embryonated eggs from contaminated soil.
Worldwide, primarily human to human transmission. Infection with the helminth T. trichiura (whipworm) is more common in warm, moist areas of the world and is often seen in conjunction with Ascaris infections. Worm burdens vary considerably, those individuals having few worms being unaffected by the presence of these parasites. Prevalence rates of 20 to 25% have been reported from the southern United States.
Trichuris dysentery syndrome develops in some children because they have a defect in antiparasite cell‑mediated immunity. Probably both cellular and humoral responses are required to eliminate the worms from the colon.
The differential diagnosis of chronic diarrhea requires consideration of several diseases, including celiac disease, inflammatory bowel disease, and irritable bowel syndrome. Abdominal cramps, rectal tenesmus or rectal prolapse (children) may occur.
Patients infected with T. trichiura may present with a chronic dysentery-like syndrome if they have a massive infestation leading to anemia and growth retardation. In some cases, diarrhea may last for years without blood and mucus. However, once blood is evident, medical intervention may occur; in some cases, the diagnosis may require colonoscopy. Also, in these cases, prolonged therapy may be necessary to eliminate the parasites. Most infections are light to moderate, with minimal or no symptoms.
Charcot‑Leyden crystals are present in the stool in patients with dysentery, a peripheral eosinophilia on the differential smear is not always seen and the degree of eosinophilia may not correlate with the severity of infection (it rarely exceeds 15%). Heavy infections tend to be rare in developed countries, and complications requiring surgical intervention are also rarely described.
Stool: The standard O&P examination is the recommended procedure for recovery and identification of T. trichiura eggs in stool specimens, primarily from the wet preparation examination of the concentration sediment. Occasionally typical eggs may be seen on the permanent stained smear; however, the morphology may be somewhat distorted.
Stool: The standard O&P examination is the recommended procedure for recovery and identification of T. trichiura eggs in stool specimens, primarily from the wet preparation examination of the concentration sediment. Most whipworm infections can be easily diagnosed by finding these characteristic eggs in the stool. The eggs can be quantitated (rare, few, moderate, many), since light infections usually cause no problems and do not require therapy.
Egg: The eggs are barrel shaped with clear, mucoid‑appearing polar plugs. They measure 50 to 54 µm long and 22 to 23 µm wide. They are passed in the unsegmented stage and require 10 to 14 days in moist soil for embryonation to occur. Distorted eggs that are much larger than normal have been seen following therapy with mebendazole and with other drugs. This is not a common finding, but something to consider if distorted eggs are seen. There are also some reports in the literature that T. vulpis (dog whipworm) eggs have been recovered in human stools. These eggs tend to be larger (70 to 80 µm long by 30 to 42 µm wide) and have prominent but small polar plugs compared with those of T. trichiura. These nematode eggs are probably the easiest to identify; the shape is very consistent in wet preparations and the eggs also maintain their shape in permanent stained smears. However, on the permanent stained smear, they tend to stain dark and may be mistaken for debris.
Adult worm: These nematodes are much larger than the pinworms, measuring 35 to 50 mm long (female) and 30 to 45 mm long (male); the male has a 360° coil at the caudal extremity. The adult worms are rarely recovered from the stool, since they are attached to the wall of the intestine. The head portion of the worm is very thin and is embedded in the mucosa, while the posterior end is much thicker and lies free in the lumen of the large intestine. The large, posterior end has been described as the whip handle, while the thin, anterior end is the whip itself, thus the name whipworm. It is unusual to find the adult worms in the stool unless the infection is quite severe with a very heavy worm burden. The majority of cases are diagnosed on the presence of the typical eggs.
Trichuris trichiura eggs present (in cases where the eggs are quantitated/rare/few/mod/many, therapy may not be required in light infections; however, in most cases treatment is given regardless of the number of eggs present)
People with helminth infections will exhibit altered immunological antigen responses. It has also been shown in animal models that helminths prevent or improve colitis through the induction of regulatory T cells and modulatory cytokines. The use of Trichuris suis in the therapy of ulcerative colitis has been a controversial and debated issue for several years. However, studies have shown improvement in 43.3% of patients with ova treatment compared with 16.7% who received placebo. This is an ongoing issue and newer information continues to become available.
Garcia, L.S. 2007. Diagnostic Medical Parasitology, 5th ed., ASM Press, Washington, D.C.
Improved hygiene, adequate disposal of fecal waste, adequate washing of contaminated fruits and vegetables