What are the presenting features and diagnosis of schistosomiasis?

Presenting Features and Diagnosis of Schistosomiasis

Schistosomiasis presents with distinct clinical manifestations depending on the stage of infection and species involved, with diagnosis requiring a combination of serological testing, microscopy of stool or urine samples, and consideration of exposure history.

Clinical Presentations

Acute Schistosomiasis (Katayama Syndrome)

• Occurs 2-8 weeks after exposure in newly infected travelers 1
• Characterized by fever, dry cough, urticarial rash, diarrhoea, and headache 1
• Marked eosinophilia is typical, sometimes exceeding 5 × 10⁹/L, though occasionally absent 1
• Self-limiting over a period of a few weeks 1

Intestinal Schistosomiasis (S. mansoni, S. japonicum, S. intercalatum, S. guineensis, S. mekongi)

• Often asymptomatic in mild cases 1
• Chronic or intermittent abdominal pain, weight loss, and diarrhoea 1
• Heavy infections may cause dysenteric illness, intestinal obstruction, or bleeding 1
• Chronic colonic ulceration can lead to iron deficiency anemia 1
• Hepatosplenic schistosomiasis can develop with:
  • Hepatosplenomegaly 1
  • Hepatic "pipestem" fibrosis 1
  • Portal hypertension with esophageal varices 1, 2
  • Preserved liver architecture despite periportal fibrosis 2

Urinary Schistosomiasis (S. haematobium)

• Often presents with haematuria, proteinuria, dysuria 1
• May cause haematospermia and inter-menstrual bleeding 1
• Long-term complications include obstructive uropathy, bladder stones, and increased risk of squamous cell carcinoma of the bladder 1

Neurological Manifestations

• Acute myelopathy (most common neurological presentation) 1
• Rapidly progressive transverse myelitis affecting the conus medullaris and cauda equina 1
• Symptoms include lower limb pain, lower motor dysfunction, bladder paralysis, and bowel dysfunction 1
• Cerebral disease (primarily with S. japonicum) presents with seizures, motor/sensory impairment, or cerebellar syndrome 1

Dermatological Manifestations

• Cercarial dermatitis ("swimmer's itch") - itchy maculopapular rash occurring hours after exposure 1
• Urticarial rash during acute schistosomiasis 1

Diagnostic Approach

Exposure History

• Fresh water exposure in endemic areas (Africa, Arabian Peninsula, South America, China, Philippines, Indonesia) 1
• Travel to high-risk locations such as the great lakes of East and southern Africa (Lakes Malawi, Victoria, Okavango delta) 1

Laboratory Investigations

• Complete blood count - eosinophilia is a key finding, especially in acute infection 1
• Serology:
  • Becomes positive at 4-8 weeks post-infection (may take up to 22 weeks) 1
  • Shows significant cross-reactivity among helminths, reducing specificity 3
  • May remain positive for many years after successful treatment, limiting usefulness for treatment monitoring 1, 4

Parasitological Examination

• For intestinal schistosomiasis:
  • Concentrated stool microscopy to detect eggs (low sensitivity) 1
  • Faecal PCR offers improved sensitivity 1
• For urinary schistosomiasis:
  • Microscopy of nitrocellulose-filtered terminal urine (midday collection increases sensitivity) 1
  • Urine dipstick for microscopic haematuria and proteinuria has low sensitivity 1

Imaging Studies

• Abdominal ultrasound to assess hepatosplenic involvement and portal hypertension 1
• Chest radiograph may show nodules and infiltrates in acute schistosomiasis 1
• MRI with contrast for suspected neuroschistosomiasis 1

Tissue Biopsy

• Rectal or colonic biopsy may reveal Schistosoma eggs in the mucosa 5
• Liver biopsy can confirm hepatic schistosomiasis 2

Diagnostic Pitfalls to Avoid

• Relying solely on stool or urine microscopy in early infection (eggs may not be detectable) 1
• Using serology alone to assess treatment success (antibodies persist for years) 4
• Misdiagnosing intestinal schistosomiasis as inflammatory bowel disease due to similar colonoscopic patterns 5
• Failing to consider schistosomiasis in migrants and travelers from endemic regions presenting with eosinophilia 2
• Overlooking the possibility of co-infections with other parasites 1

Diagnostic Algorithm

1. For patients with relevant exposure history and compatible symptoms:

   • Order complete blood count to check for eosinophilia 1
   • Request serology for schistosomiasis 1
   • Collect stool samples for microscopy and/or PCR (for S. mansoni, S. japonicum) 1
   • Collect terminal urine sample (for S. haematobium) 1

2. If acute presentation (2-8 weeks post-exposure):

   • The combination of eosinophilia with fever and rash after freshwater swimming in endemic areas makes the diagnosis likely even if serology and microscopy are negative 1

3. For chronic presentation:

   • Persistent symptoms with positive serology but negative microscopy warrants further investigation 1
   • Consider endoscopy with biopsy for intestinal symptoms 5
   • Consider ultrasound for hepatosplenic assessment 1
   • Consider MRI for neurological symptoms 1