Schistosomiasis (Bilharziasis)

Key Features

Essentials of Diagnosis

• History of freshwater exposure in an endemic area

• Acute schistosomiasis: fever, headache, myalgias, cough, urticaria, diarrhea, and eosinophilia

• Intestinal schistosomiasis: abdominal pain, diarrhea, and hepatomegaly, progressing to anorexia, weight loss, and features of portal hypertension

• Urinary schistosomiasis: hematuria and dysuria, progressing to hydronephrosis and urinary infections

• Diagnosis: characteristic eggs in feces or urine; biopsy of rectal or bladder mucosa; positive serology

General Considerations

• Intestinal schistosomiasis, with infection of mesenteric venules, caused by

  • Schistosoma mansoni, which is present in Africa, the Arabian peninsula, South America, and the Caribbean

  • Schistosoma japonicum, which is endemic in China and Southeast Asia

  • Schistosoma mekongi, which is endemic near the Mekong River in Southeast Asia

  • Schistosoma intercalatum and Schistosoma guineensis, which occur in parts of Africa

• Urinary schistosomiasis, with infection of venules of the urinary tract

  • Caused by Schistosoma haematobium

  • Endemic in Africa and the Middle East

• Transmission is focal, with greatest prevalence in poor rural areas

• Humans are infected with schistosomes after contact with freshwater containing cercariae released by infected snails

• Chronic infection can result in scarring of mesenteric or vesicular blood vessels, leading to portal hypertension and alterations in the urinary tract

• Acute schistosomiasis

  • May occur in previously uninfected individuals

  • Febrile illness develops 2–8 weeks after infection

Demographics

• Affects more than 200 million persons worldwide, leads to severe consequences in 20 million persons and about 100,000 deaths annually

• Prevalence of infection and illness typically peaks at about 15–20 years of age

Clinical Findings

• Cercarial dermatitis

  • Localized erythema develops in some individuals, which can progress to a pruritic maculopapular rash that persists for some days

  • Dermatitis can be caused by human schistosomes and, in nontropical areas, by bird schistosomes that cannot complete their life cycle in humans (swimmer's itch)

• Acute schistosomiasis (Katayama syndrome)

  • A febrile illness may develop 2–8 weeks after exposure in persons without prior infection, most commonly after heavy infection with S mansoni or S japonicum

  • Presenting symptoms and signs include

    • Acute onset of fever

    • Headache

    • Myalgias

    • Cough

    • Malaise

    • Urticaria

    • Diarrhea, which may be bloody

    • Hepatosplenomegaly

    • Lymphadenopathy

    • Pulmonary infiltrates

  • Localized lesions may occasionally cause severe manifestations, including CNS abnormalities and death

• Chronic schistosomiasis

  • Many infected persons have light infections and are asymptomatic

  • However, an estimated 50–60% of patients have symptoms and 5–10% have advanced organ damage

  • Asymptomatic infected children may suffer from anemia and growth retardation

  • Intestinal schistosomiasis

    • Symptomatic patients typically experience abdominal pain, fatigue, diarrhea, and hepatomegaly

    • Over years, anorexia, weight loss, weakness, colonic polyps, and features of portal hypertension develop

    • Late manifestations include hematemesis from esophageal varices, hepatic failure, and pulmonary hypertension

  • Urinary schistosomiasis

    • May present within months of infection with hematuria and dysuria, most commonly in children and young adults

    • Fibrotic changes ...