Case Study: Schistosomiasis
Dr. Jennifer Coetzee
CMID / Ampath
Clinical Presentation
• 8 year old boy
• Referred to renal clinic from peripheral hospital
• Two year history of painless, macroscopic hematuria
• Urine microscopy: eggs of Schistosoma haematobium
Objectives
• Describe the life cycle of the bilharzia parasite
• Discuss the pathogenesis of bilharzia as a prototype of a parasitic infection
• Briefly describe the principles of the diagnosis and management of this infection
Ross A et al. N Engl J Med 2002;346:1212-1220
Life Cycle of the SchistosomeLife Cycle of the Bilharzia Parasite
Pathophysiology and Clinical Disease
• Acute disease:– Cercarial dermatitis after penetration of the
cercaria– “Swimmers itch” if cercaria from birds involved– After onset of egg laying, may develop acute
reaction (Katayama fever) if never exposed before
– Symptoms resolve as immune system adapts
Chronic Stages
• Eggs entrapped in host tissues secrete antigens
• Incite an inflammatory granulomatous response
• Granulomas eventually replaced by dense fibrosis obstruct blood flow
• Clinical symptoms vary according to species, total worm burden, patient’s stage of health at time of infection
Gastrointestinal Complications
• Wall of distal colon damaged as eggs pass through, become lodged
• Inflammatory response can cause focal ulcers or polyps
• May develop diarrhoea, abdominal pain or colitis
• ?Predisposing factor for colorectal carcinoma
Hepatosplenic Complications
• Eggs may incite granulomatous response in liver
• May become walled off with dense layers of fibrous tissue
• Pipestem fibrosis - obstructs portal veins
• Leads to portal hypertension, oesophageal varices, splenomegaly
Genitourinary Complications
• Eggs lodged in bladder wall - inflammatory infiltrate around the egg
• Overlying bladder epithelium hyperplastic, polyps
• Polyps erode, ulcerate - cause hematuria
• Log standing and severe infections may lead to carcinoma
• Fibrosis may lead to ureteric stricturing, hydronephrosis
Ross A et al. N Engl J Med 2002;346:1212-1220
Clinical Findings in Two Patients Infected with Schistosoma Species
Other Complications
• Cardiopulmonary Complications:– Eggs from shunted portosystemic blood lodged
in pulmonary arterioles– Granuloma formation, pulmonary hypertension,
cor pulmonale
• Central nervous system:– Eggs deposited in spinal column transverse
myelitis-like syndrome
Laboratory Diagnosis• Microscopy
– Detection of eggs in wet mounts of stool or urine– S. manoni has a lateral spine, S. haematobium has a
terminal spine
• Rectal or bladder biopsies may be necessary• Also antigen and antibody detection
– Antibodies cross react with other helminth infections– Problematic in endemic areas
Kaplan B and Meyers K. N Engl J Med 2000;343:1085
An eight-year-old boy was referred to the nephrology clinic with a two-year history of painless, gross macroscopic hematuria
Management and Prevention
• Anti-schistosomal drugs– Praziquantel
• Symptomatic management of complications
• Chemoprophylaxis available
• Vaccines under development
• Snail control!
Bibliography
• Ross A.G.P., Bartley P.B. et al. Schistosomiasis. New Eng J Med 2002; 346(16): 1212-1219
• Coon D.R. Schistosomiasis: Overview of the history, biology, clinicopathology, and laboratory diagosis. Clin Micro Newsletter 27(21): 163-169
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