Contents
Introduction
Schistosomiasis, also known as snail fever and bilharzia, is a disease caused by parasitic flatworms called schistosomes.
History
Epidemiology
The disease is endemic in about 75 developing countries and mainly affects people living in rural agricultural and peri-urban areas.
Aetiology
- S. mansoni/S. japonicum
- S. haematobium
Pathophysiology
Lifecycle
Clinical features
Initial symptoms:
- Swimmer’s itch
- Initial itching/tingling and rash at infection site
- Within 12 hours
- 2-10 weeks later:
- Fever, chills and muscle aches
- Aching
- Dry cough
- Diarrhoea
- Hepatosplenomegaly
- Lymphadenopathy
Acute schistosomiasis (Katayama fever):
Occur weeks/months after the initial infection as systemic reaction against migrating schistosomulae as they pass through the bloodstream through the lungs to the liver.
- Dry cough (with changes on chest X-ray)
- Fever, malaise, muscle aches
- Abdominal pain
- Hepatosplenomegaly
Chronic disease:
In long established disease, adult worms lay eggs that can cause inflammatory reactions (eosinophilic reactions, proteolytic enzyme actions, etc).
- Depending on site:
Genitourinary disease:
- Frequent, painful or bloody urine (10 to 12 weeks after infection)
- Inflammation and scarring of the bladder
- Later: Fibrosis → Urinary tract obstruction, hydronephrosis, and kidney failure
Gastrointestinal disease:
- Abdominal pain and bloody diarrhoea (especially in children)
- Severe disease: Narrowing of the colon/rectum
- Later: Fibrosis → Cirrhosis (4-8 % cases)
Central nervous system disease:
- Brain: Seizures
- Spinal cord: Transverse myelitis + flaccid paraplegia
| Clinical pathology due to schistosomiasis (WHO) | ||
| Morbidity | S. mansoni/S. japonicum | S. haematobium |
| General | Acute schistosomiasis | Acute schistosomiasis |
| Anaemia | Anaemia | |
| Organ-specific pathology | Hepatomegaly | Vesicular wall hardening |
| Splenomegaly | Bladder cancer | |
| Ectopic egg granulomas | Ectopic egg granulomas | |
| Alternative venous circulation | Kidney malfunction | |
| Genital schistosomiasis | Genital schistosomiasis | |
| Developmental impairment | Cognitive dysfunction | Cognitive dysfunction |
| Delayed growth/stunting | Delayed growth/stunting |
Complications
- Secondary blood disorders in cases of colon damage
- Where infection persists, bladder cancer may develop
- Children can develop anaemia, malnutrition and learning disabilities
Diagnosis
X-ray pelvis:
Tissue biopsy:
Management
Prevention:
Treatment:
- Praziquantel
- Oxamniquine
Community management:
WHO guidelines for community treatment:
- Everyone in the village receives treatment:
- When >50% of village children have bloody urine
- Only school-age children are treated:
- When 20-50% of children have bloody urine
- Mass treatment is not implemented:
- When <20% of children have symptoms
