Urinary schistosomiasis

Abstract

Schistosomiasis is the second most common socio-economically devastating parasitic disease after malaria, affecting about 240 million residents of developing countries. In Africa, it predominantly manifests as urogenital disease, and the main infective agent is Schistosoma hematobium. Endemicity is propagated by poor socio-economic status and environmental degradation due to rapid urbanization. Recreational swimming is a potent medium for the spread of disease in children and adolescents. Most affected individuals are asymptomatic. The male and female worms are equipped with an extraordinary capacity for immune evasion and are able to co-habit for several decades within the pelvic venous plexus. Eggs deposited in the bladder wall resist elimination by type 1T lymphocytes. Instead, they are sustained by pro-fibrogenic encapsulation (as modulated by type 2 helper cells). Progressive bladder disease results in obstructive uropathy and predisposes to (mostly) squamous cell carcinoma. Schistosomal glomerulopathy manifests as a clinical spectrum of asymptomatic proteinuria, nephrosis and/or nephritic syndrome. Findings on renal biopsy may be influenced by co-morbidity with Salmonella bacteria, amyloidosis and hepatitis C infection. Potentially fatal Katayama fever and spinal radiculopathy may ensue in tourists visiting an endemic zone. Early detection by urine microscopy is hampered by low urinary excretion rates of the parasite eggs. Although useful in travelers with newly acquired disease, the results of the serological antibody assay may be false positive in residents of an endemic zone. Cystoscopy, however, may be invaluable. Due to its safety, effectiveness and once-daily dosing, praziquantel is the drug of choice. An integrated approach that includes mass chemotherapy, environmental health programs and public health education is the most cost-effective preventive strategy.