Treatment of Schistosomiasis
For schistosomiasis, treat with praziquantel 40 mg/kg orally as a single dose for S. mansoni, S. intercalatum, and S. guineensis infections, or 60 mg/kg divided into two doses on the same day for S. japonicum and S. mekongi infections, with a mandatory repeat dose at 6-8 weeks to eliminate immature parasites. 1, 2
Species-Specific Dosing Regimens
The treatment approach depends critically on identifying the infecting Schistosoma species:
For African and South American species:
- S. mansoni, S. intercalatum, and S. guineensis: Praziquantel 40 mg/kg orally as a single dose on day 1, then repeat at 6-8 weeks 1, 2
- This single-day dosing applies to most cases diagnosed in the UK, as they are typically acquired in Africa 1
For Asian species:
- S. japonicum and S. mekongi: Praziquantel 60 mg/kg orally divided into two doses on the same day, then repeat at 6-8 weeks 1, 2
- The higher dose is necessary due to reduced sensitivity of these species 1
When species is uncertain:
- If diagnosis is based on serology alone from the Asia-Pacific region, use the higher 60 mg/kg regimen in two divided doses to ensure adequate coverage 1, 2
Critical Timing: The Two-Dose Requirement
The repeat dose at 6-8 weeks is mandatory, not optional. 1, 2 This is because:
- Immature schistosomules and eggs are relatively resistant to praziquantel 1, 2
- A single treatment will miss parasites that were immature at the time of initial dosing 2
- Failure to repeat treatment leads to persistent infection and treatment failure 2
Acute Schistosomiasis (Katayama Syndrome)
When patients present with acute schistosomiasis 2-8 weeks after freshwater exposure in Africa with fever, eosinophilia (often >5 × 10⁹/L), dry cough, and urticarial rash: 1
Treatment protocol:
- Oral prednisolone 20 mg daily for 5 days to reduce symptom duration 1, 2
- Praziquantel 40 mg/kg as a single dose at diagnosis 1, 2
- Mandatory repeat praziquantel dose at 6-8 weeks due to resistance of immature forms 1, 2
Critical pitfall to avoid: Do not administer praziquantel during acute Katayama syndrome without corticosteroids, as this may worsen inflammatory symptoms 2. However, always screen for strongyloidiasis before starting corticosteroids to prevent hyperinfection syndrome 2.
Neuroschistosomiasis
For CNS involvement, the regimen differs substantially: 2
- Praziquantel 40 mg/kg twice daily for 5 days (not the standard single-dose regimen) 2
- Dexamethasone 4 mg four times daily, reducing after 7 days, for a total duration of 2-6 weeks 2
- In acute neuroschistosomiasis, give corticosteroids first before anthelmintic therapy 2
Important caveat: Dexamethasone may reduce praziquantel levels through increased metabolism, requiring careful monitoring 2
Treatment Failure and Monitoring
Do not use serology to assess treatment success — antibodies persist for many years after successful parasite eradication and will remain positive indefinitely 1, 2, 3, 4
If viable eggs persist after completing both doses:
- Consider true treatment failure 2
- Seek specialist advice rather than repeating standard dosing 2
- Consider combination therapy with artemisinin derivatives, though clinical trial evidence is limited 2
Common Clinical Pitfalls
- Failing to adjust dosage based on species: Using 40 mg/kg for S. japonicum or S. mekongi leads to treatment failure 2
- Omitting the 6-8 week repeat dose: This is the most common cause of persistent infection 2
- Using serology for treatment monitoring: This will falsely suggest treatment failure for years after successful cure 1, 2
- Treating Katayama syndrome without steroids: This worsens inflammatory symptoms 2
- Starting steroids without ruling out strongyloidiasis: This can precipitate fatal hyperinfection syndrome 2
Special Populations
For pregnancy, lactation, or immunocompromised patients, seek specialist advice for dosing adjustments, though praziquantel is generally considered safe with few or transient mild side effects 1, 5, 6