Mortality in urinary schistosomiasis

Case-Control Study of Posttreatment Regression of Urinary Tract Morbidity Among Adults in Schistosoma haematobium-Endemic Communities in Kwale County, Kenya

Previous population-based studies have examined treatment impact on Schistosoma-associated urinary tract disease among children, but much less is known about longer-term treatment benefits for affected adult populations in areas where risk of recurrent infection is high. In communities in Msambweni, along the Kenya coast, we identified, using a portable ultrasound, 77 adults (aged 17-85) with moderate-to-severe obstructive uropathy or bladder disease due to Schistosoma haematobium. Treatment response was assessed by repeat ultrasound 1-2 years after praziquantel (PZQ) therapy and compared with interval changes among age- and sex-matched infected/treated control subjects who did not have urinary tract abnormalities at the time of initial examination. Of the 77 affected adults, 62 (81%) had improvement in bladder and/or kidney scores after treatment, 14 (18%) had no change, and one (1.3%) had progression of disease. Of the 77 controls, 75 (97%) remained disease free by ultrasound, while two (3%) had apparent progression with abnormal findings on follow-up examination. We conclude that PZQ therapy for S. haematobium is effective in significantly reducing urinary tract morbidity from urogenital schistosomiasis among adult age groups, and affected adults stand to benefit from inclusion in mass treatment campaigns.

Human schistosomiasis

Schistosomiasis or bilharzia is a tropical disease caused by worms of the genus Schistosoma. The transmission cycle requires contamination of surface water by excreta, specific freshwater snails as intermediate hosts, and human water contact. The main disease-causing species are S haematobium, S mansoni, and S japonicum. According to WHO, 200 million people are infected worldwide, leading to the loss of 1.53 million disability-adjusted life years, although these figures need revision. Schistosomiasis is characterised by focal epidemiology and overdispersed population distribution, with higher infection rates in children than in adults. Complex immune mechanisms lead to the slow acquisition of immune resistance, though innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is mostly seen in travellers after primary infection. Chronic schistosomal disease affects mainly individuals with long-standing infections in poor rural areas. Immunopathological reactions against schistosome eggs trapped in the tissues lead to inflammatory and obstructive disease in the urinary system (S haematobium) or intestinal disease, hepatosplenic inflammation, and liver fibrosis (S mansoni, S japonicum). The diagnostic standard is microscopic demonstration of eggs in the excreta. Praziquantel is the drug treatment of choice. Vaccines are not yet available. Great advances have been made in the control of the disease through population-based chemotherapy but these required political commitment and strong health systems.

Urinary tract morbidity due to Schistosoma haematobium infection in Mali

A total of 824 Malian villagers in a region endemic for Schistosoma (S.) haematobium were examined clinically, parasitologically and by abdominal ultrasound. Systematic schistosomicidal treatment had never been applied to this population. Prevalence of S. haematobium infection ranged from 77% in adolescents to 51% in adults older than 40 years. Intensity of infection was generally mild, 91% of all patients excreting less than 100 ova/10 ml urine. Bladder wall enlargement and irregularities, bladder masses, pseudopolyps and dilation of the upper urinary tract were found ultrasonographically in about one third of infected individuals. Bladder lesions were more frequent in children than in adults and correlated with the intensity of infection in younger age groups only. Hydronephrosis was rare (7 of 824) and never seen in uninfected individuals. Prevalence of urinary tract pathology dropped significantly with age (P < 0.001) and was lowest in patients older than 40 years. Logistical regression identified age and infection as independent parameters affecting the prevalence of urinary tract pathology (P < 0.001). We conclude that Schistosoma haematobium infection causes substantial morbidity in children and younger adults. The reduction of urinary tract morbidity with age despite a considerable prevalence of infection in older age groups suggests spontaneous resolution during adulthood in most cases.

Ultrasound in schistosomiasis — A critical look at methodological issues and potential applications

This is the concluding paper of a series on the use of diagnostic ultrasound in the investigation of schistosomiasis. An earlier chapter in the volume discussed standardization of the methodology, and of recording, when ultrasound is used for epidemiological purposes. The present paper discusses some other requirements for obtaining ultrasound data which can be used to make valid comparisons within and between studies. Since there is an inherent variability in the interpretation of results from ultrasound images, quality control and the training of observers are both essential. It is also necessary to collect more information for each endemic setting about possible concomitant diseases which might lead to misinterpretation of results. Furthermore, the analysis of the data obtained must be uniform if valid comparisons are to be made. A final section considers applications of ultrasonography in research and control programmes. The technique should make it possible to obtain a better understanding of the extent and distribution of organ damage due to schistosomal infection in different geographical areas, and of the way in which lesions develop over time, or may regress in response to treatment. Since ultrasonography will always remain a relatively labour-intensive and expensive technique, it is necessary to establish, in different settings, how its findings correlate with the results of parasitological, serological and biochemical tests. The ultimate aim is to build up a body of information on the potential of ultrasonography, in combination with other procedures, in the various possible approaches to morbidity control.

Reversibility of urinary tract abnormalities due to Schistosoma haematobium infection

In view of the controversial results regarding reversibility of urinary tract lesions due to Schistosoma haematobium infection, 103 patients in the People's Republic of Congo were followed up one year after treatment with Praziquantel (40 mg/kg body wt) by means of ultrasonography. The study group consisted mainly of children. Before therapy a total of 113 lesions were detected in the lower urinary tract. These consisted of bladder wall enlargements (N = 53), enlargements of the bladder wall in combination with singular (N = 16) or multiple polyps (N = 30), vesical calcifications (N = 10), and cases with cystitis cystica (N = 4). One year after therapy, a drastic reduction of ova output was observed, and only eight pathological abnormalities of the lower urinary tract were still detectable. Vesical calcifications persisted in four out of ten cases. Urinary tract obstructions of different degrees (N = 42) showed a comparably marked reversibility. It was concluded that, in children, the resolution of bladder lesions induced by urinary schistosomiasis resulted in reversibility of urinary tract obstructions one year after treatment with Praziquantel.

The pathobiology of Schistosoma haematobium infection in humans

Schistosoma haematobium infection is a common occurrence in Africa and the Middle East and is the world's leading cause of hematuria. Since more North Americans are venturing into endemic areas and more residents of endemic areas are seeking medical care in North America, pathologists must be able not only to diagnose urinary schistosomiasis but also to provide advice as to further therapy. These endeavors mandate knowledge of the pathobiologic features of the disease. The severity and frequency of the sequelae of urinary schistosomiasis (hydroureter, hydronephrosis, bladder ulcer, and polyposis) and of its complications (bacterial urinary tract infection, renal failure, urothelial cancers) depend on the intensity of infection, i.e., worm burden and tissue egg burden, and the duration of infection. Significant differences in gross and microscopic morphology, clinical laboratory findings, and optimal mode of treatment exist between active (during active egg deposition) and inactive (after cessation of oviposition) disease. Moreover, nearly half of the severe sequelae and complications occur during the inactive phase of the disease, when diagnosis is most difficult. The manifestations of this disease are manifold and complex, and firm understanding of the pathobiologic features is necessary if pathologists are to understand their role in the direction of treatment.

Renal disease due to schistosomiasis of the lower urinary tract

The literature concerning renal impairment and damage due to vesical schistosomiasis has been reviewed, with emphasis on radiologic, biochemical, and renographic studies of renal function in affected persons. Presently available evidence suggests that infections due to S. haematobium constitute an important public health problem because they are widely prevalent. A high proportion of affected persons suffer renal impairment and damage due to obstructive uropathic lesions in the lower urinary tract and, probably, through direct immunologic involvement of the kidney. It is therefore important that efforts should be intensified to better define the size and scope of the problem, and to control the disease.