Schistosomiasis
🐛 Schistosomiasis (Bilharzia) is caused not by the worms themselves but by the immune response to their eggs.
💊 Praziquantel is the treatment of choice - it can reverse up to 90% of organ damage if given promptly.
⚠️ Katayama fever may progress to neurological complications → treat early.
🌍 About
- Caused by parasitic worms living in fresh water snails.
- Also known as Bilharzia.
💧 Sources of Infection
- Ponds, lakes, rivers, reservoirs, canals.
- Showers with unfiltered lake/river water.
- Not acquired from sea water or chlorinated swimming pools.
📌 Geographical Distribution
- Endemic in Africa, South America, the Caribbean, the Middle East, and Asia.
🦠 Microbiology
- Schistosoma mansoni → intestinal & liver disease.
- Schistosoma haematobium → bladder disease, ↑ risk of bladder cancer.
- Schistosoma japonicum → intestinal & liver disease.
🔄 Lifecycle
- Parasite lives in freshwater snails.
- Snails release invasive form = cercariae.
- Infection via direct skin contact → worms burrow through skin.
- Parasites migrate to liver, bowel, bladder → release eggs in urine/faeces.
⚡ Acute Infection
- Often asymptomatic.
- Initial “swimmer’s itch” = itchy papular rash at entry site.
- Weeks later: fever, urticaria/rash, cough, diarrhoea, myalgia, malaise.
🌡️ Katayama Fever (Acute Schistosomiasis)
- Seen 4–8 weeks post exposure (esp. *S. mansoni*).
- Due to hypersensitivity reaction as parasites migrate through portal & pulmonary circulation.
- Features: fever, eosinophilia, serum-sickness type illness.
- Stool microscopy often negative (low egg burden); serology useful in non-endemic settings.
⏳ Chronic Infection
- Anaemia, abdominal pain, hepatosplenomegaly, portal hypertension.
- GI: diarrhoea, blood in stool, colonic polyps/strictures.
- GU: cystitis, dysuria, haematuria; risk of bladder cancer (S. haematobium).
- Neuro: seizures, weakness, leg numbness.
🧪 Investigations
- Bloods: Anaemia, eosinophilia; U&E (immune complex nephritis); LFTs (hepatitis).
- CXR: Pulmonary infiltrates, granulomas.
- Stool/urine microscopy: Detect ova (may need concentration methods).
- Serology: Helpful early & in travellers from non-endemic areas.
💊 Management
- Praziquantel = treatment of choice (single-day course, often repeated).
- Best given once worms have matured (weeks after exposure); may require repeat dosing.
- Corticosteroids can be used in acute Katayama fever or neurological disease to dampen inflammation.
- Early treatment reverses much organ damage within months.
