Schistosoma

From IDWiki
Schistosoma

Background

  • Infection with a species of the genus Schistosoma

Microbiology

Risk Factors

  • Fresh water exposure in endemic countries

Epidemiology

  • Seroprevalence in migrants by region of originasundi2019pr
    • Latin America and the Caribbean (20%; 9-34)
    • Middle East and north Africa (6.4%; 0.3-19.5)
    • Sub-Saharan Africa (24.1%; 16-33)
    • South Asia (0%; 0-69)
    • East Asia and the Pacific (5.4%; 2-10)

Clinical Manifestations

Swimmer's Itch

  • Cercariae penetrate exposed skin and cause prickling sensation and occasionally urticaria, followed hours later by a macular rash
  • Caused by schistosomes that do not cause systemic illness
  • Common in Great Lakes region of North America, New England in the US, and other parts of North America and Europe

Katayama Fever

  • Syndrome of acute schistosomiasis that follows 4 to 8 weeks (range 2 to 12 weeks), after the flukes have migrated, developed into adults, and have started producing eggs
  • The syndrome represents a hypersensitivity reaction to the eggs produced by adult worms
  • More common with Schistosoma japonicum and Schistosoma mansoni, and less common with Schistosoma haematobium
  • Symptoms include abrypt onset of fever, chills, fatigue, headache, myalgias, abdominal pain, diarrhea, and occasionally bloody stool
  • Most also develop cough, dyspnea, chest pain, and diffuse infiltrates on chest x-ray
    • Lung nodules contain granulomas around eggs
  • Hepatomegaly, splenomegaly, and lymphadenopathy are common
  • Eggs may not be seen in stool until later in the course of the disease
  • Symptoms usually resolve within 2 to 10 weeks
  • Can involve symptoms anywhere the worms migrate and deposit eggs: CNS, genital tract, and skin
    • However, an induced small-vessel vasculitis can also cause neurological symptoms

Chronic Schistosomiasis

  • Can be asymptomatic or paucisymptomatic
  • Chronic granulomatous inflammation causes weight loss, anemia, stunted growth
  • Eosinophilia is common

Investigations

  • Labs
    • CBC, showing eosinophilia
    • Schisto serology (only positive 6 weeks after infection)
    • Egg detection in stool, urine, semen, or tissue biopsy
  • Imaging
    • Eggs can cause granulomatous disease in various organs
    • Bladder polyps and obstruction may be seen on ultrasound

Diagnosis

  • Usually based on serology

Management

  • Acute
  • Chronic
    • Praziquantel 20-40 mg/kg or 40-60 mg/kg (if at risk for S. japonica)
    • Given over one day split into 3 doses, then repeated 6 weeks later

Prognosis

  • Increased risk of squamous cell carcinoma, which increase with young age at infection, duration of infection, high burden of infection, and bladder wall fibrosis