Trichuriasis

Definition, Etiology, PathogenesisTop

1. Etiologic agent: Nematode Trichuris trichiura (whipworm). Adult worms measure 3 to 5 centimeters in length. Females produce thousands of eggs daily, which become invasive after ~3 weeks of cleavage in moist soil with low light. Once ingested, they travel to the small intestine and release larvae. The larvae penetrate the villi and, after 2 or 3 days, migrate to the colon. T trichiura achieves final maturation after ~3 months. The parasite colonizes the human large intestine from the cecum to the rectum. It produces proteins that cause fusion of intestinal epithelial cells, leading to the formation of pores into which the parasite threads with its thinner, anterior end. The distal part protrudes into the intestinal lumen. The host’s immune response develops at the port of entry, which may result in ulceration and mucosal bleeding.

2. Reservoir and transmission: Human is the only reservoir of T trichiura. The parasite is a geohelminth, which means that invasions are transmitted via soil contaminated with human feces. Humans may become infected through consumption of unwashed fruit and vegetables or soil-contaminated water. Poor hand hygiene following work with soil or playing in a sandbox may cause food contamination.

3. Incubation and contagious period: The eggs are not invasive at the time of excretion with stool. Therefore, direct human-to-human transmission is impossible.

EPIDEMIOLOGYTop

T trichiura is a cosmopolitan parasite. High-intensity invasions occur in tropical and subtropical zones, in particular in sub-Saharan Africa, the Americas, China, and East Asia. Infections are more often seen in regions with poor sanitation and hygiene practices.

Clinical Features and Natural HistoryTop

Light invasions are found in temperate or cold climate zones. They are often asymptomatic or sometimes manifest with mild anemia, abdominal pain, diarrhea, or eosinophilia.

Heavy invasions typically occur in tropical regions. They manifest with significant anemia, weight loss, abdominal pain, persistent diarrhea with blood and mucus. Neurologic manifestations mimicking epilepsy and large intestine ulcerations may develop in children.

DIAGNOSISTop

Diagnostic Tests

1. Identification of the etiologic agent: Identification of T trichiura eggs in microscopic stool examination. The Kato-Miura thick smear is routinely performed. Fecal concentration techniques are also used, as identification of solitary eggs in light invasions may be difficult. Colonoscopy may help identify mature parasites.

2. Other findings: Possible eosinophilia in peripheral blood (usually up to 15%).

Differential Diagnosis

Other geohelminth infections (hookworm infections, ascariasis, strongyloidiasis), amebiasis, yersiniosis, other causes of infectious diarrhea, inflammatory bowel disease, other causes of eosinophilia.

TREATMENTTop

Antiparasitic Treatment

1) First-line treatment: Oral mebendazole 100 mg bid for 3 days, oral albendazole 400 mg once daily for 3 days, oral ivermectin 200 microg/kg/d for 3 days.

2) Alternative treatment: Oral pyrantel 11 mg/kg in a single dose, oral levamisole 150 mg/kg in a single dose, oral praziquantel 25 mg/kg in a single dose, oral piperazine (citrate) 4.5 g, 2 doses 14 days apart.

COMPLICATIONSTop

Heavy invasions with severe course may lead to colitis, gastrointestinal bleeding, or rectal prolapse.

PROGNOSISTop

In patients with light invasions the prognosis is good. In the very rare cases of heavy invasion and acute course, the disease may lead to death.

PREVENTIONTop

Specific Prevention

None.

Nonspecific Prevention

1. Proper sewage processing.

2. Avoiding the use of human feces to fertilize fruit and vegetable plantations.

3. Thorough washing of fruits and vegetables.