What is the recommended treatment for Schistosomiasis (also known as Bilharzia)?

Treatment of Schistosomiasis (Bilharzia)

Praziquantel is the drug of choice for all forms of schistosomiasis, with dosing at 40 mg/kg as a single oral dose for S. mansoni, S. haematobium, and S. intercalatum, or 60 mg/kg divided into two doses for S. japonicum and S. mekongi infections from Asia-Pacific regions. 1

Standard Treatment Regimens by Species

For S. mansoni, S. haematobium, S. intercalatum, and S. guineensis

• Administer praziquantel 40 mg/kg orally as a single dose 1
• This regimen achieves cure rates of approximately 91-93% with egg reduction rates exceeding 90% 2
• A single 40 mg/kg dose provides 76% protection across all schistosome subspecies 3

For S. japonicum and S. mekongi (Asia-Pacific Region)

• Administer praziquantel 60 mg/kg orally divided into two doses on the same day 1
• Use this higher dose for any infection diagnosed by serology alone from Asia-Pacific regions 1
• The 60 mg/kg regimen offers no significant efficacy advantage over 40 mg/kg for intestinal schistosomiasis caused by S. mansoni, but is specifically recommended for Asian species 2

Special Clinical Scenarios

Acute Schistosomiasis (Katayama Syndrome)

For acute schistosomiasis presenting 2-8 weeks after freshwater exposure with fever, rash, and eosinophilia, initiate corticosteroids first, then administer praziquantel after the acute inflammatory phase subsides. 1

Treatment algorithm:

• Start prednisolone 20-30 mg daily for 5 days to reduce symptom duration 4, 1
• Give praziquantel 40 mg/kg as a single dose after completing steroids 4
• Repeat praziquantel 40 mg/kg at 6-8 weeks post-initial treatment because immature schistosomules are relatively resistant to the first dose 4, 1
• The 6-8 week interval allows maturation of surviving parasites, making them susceptible to treatment 5

Critical pitfall: Administering praziquantel during acute Katayama syndrome without corticosteroids may worsen neurological and systemic symptoms 1

Neuroschistosomiasis

For CNS involvement with focal neurological signs, seizures, or spinal cord symptoms, use prolonged high-dose praziquantel combined with corticosteroids. 4, 1

Treatment protocol:

• Praziquantel 40 mg/kg twice daily for 5 days 1
• Dexamethasone 4 mg four times daily, reducing after 7 days over a total duration of 2-6 weeks 4, 1
• In acute neuroschistosomiasis, administer corticosteroids first before anthelmintic therapy to prevent paradoxical worsening 1

Important caveat: Dexamethasone may reduce praziquantel levels through increased metabolism, requiring the higher total dose 1

Treatment Failure or Persistent Infection

If parasitological evidence of infection persists at 6 weeks post-treatment, repeat praziquantel 40 mg/kg 5

Management approach:

• Confirm active infection through microscopy of stool (for S. mansoni/japonicum) or terminal urine (for S. haematobium) before retreating 5
• Wait the full 6-8 weeks before repeating treatment to allow immature worms to mature 5
• Consider adding prednisolone 20 mg daily for 5 days if acute symptoms are severe 5
• Two doses given 2-4 weeks apart improve cure rates from 48% to 70% and reduce infection intensity more effectively than single dosing 6, 7

Monitoring and Follow-up

Do not use serology to assess treatment success, as antibodies persist for years after cure. 1, 5

Appropriate monitoring:

• Use microscopy of stool or urine at 6 weeks post-treatment to document parasitological cure 5
• Eosinophilia typically resolves with successful treatment but may persist temporarily 8
• Serology remains positive for many years despite successful treatment and cannot distinguish active from past infection 1, 5

Critical Pitfalls to Avoid

• Never use 60 mg/kg dosing for S. haematobium or S. mansoni - this is reserved exclusively for Asian species (S. japonicum, S. mekongi) 5
• Screen for strongyloidiasis before initiating corticosteroids in patients from endemic areas, as steroids can precipitate fatal hyperinfection syndrome 1
• Do not treat too early after initial therapy - wait 6-8 weeks before repeating praziquantel to allow immature worms to mature 5
• Avoid relying on clinical symptoms alone in endemic areas where reinfection rates are high - confirm parasitological cure with microscopy 6

Safety Profile

• Both 40 mg/kg and 60 mg/kg doses are well-tolerated, though 60 mg/kg causes more adverse events (83% vs 73% experiencing at least one event within 4 hours) 2
• Most common adverse event is abdominal pain (40% at 4 hours, 24% at 24 hours post-dosing) 2
• All adverse events are mild and transient, with no severe systemic complications reported 2, 7
• Side effects cannot be reliably distinguished from disease-related symptoms 2