Background: The morbid effects of urinary bilharziasis are becoming more evident with the advent of sophisticated diagnostics such as ultrasound. However, such diagnosis of Schistosoma haematobium morbidity is often hampered by lack of funds, proper equipment, or training.
Objective: We performed a cross-sectional investigation of schoolchildren in a highly endemic area of east central Zimbabwe in order to assess the utility of a number of simple clinical indicators to predict Schistosoma haematobium morbidity.
Methods: Prevalence and intensity ofS. haematobiuminfection was determined in 551 schoolchildren, with ultrasound examination of the kidneys and bladder performed on 222. The association of a number of demographic, parasitological, and clinical parameters with clinical outcome was evaluated.
Results: Overall, 60% of the children were infected withS. haematobium. Although lacking specificity, proteinuria and parasite eggs count best predicted bladder pathology. Presence of kidney dilation was associated with fatigue and pain upon urination, but these variables were not very sensitive.
Conclusions: None of the variables assessed were ideal predictors of morbidity. However, the results suggest that a combination of inexpensive, simple indicators may allow for improved targeting of S. haematobium treatment to those with severe morbidity and better monitoring of the progress of control campaigns when more expensive diagnostic methods are not available.

An estimated 200 million people in 76 countries are infected with schistosomes. Of these, approximately 20 million suffer severe sequelae, with disease manifestations ranging from bladder carcinomas to liver fibrosis. ¹ Current health policy on schistosomiasis aims at decreasing morbidity associated with infection.^2,3 Increasing the accessibility of methods to diagnose schistosomiasis induced pathology is instrumental in meeting this goal.

For Schistosoma haematobium morbidity assessment, ultrasound examination has achieved widespread acceptance.^4,5 Field studies with portable ultrasound devices have shown that type and extent of schistosomiasis associated urinary tract pathology varies widely.^6-9 Being able to diagnose severe cases or define risk factors associated with pathology would be useful for targeting treatment and would also improve our understanding of the magnitude and etiology of such pathology. As ultrasound is a costly method of diagnosing urinary tract pathology, the current study assesses the utility of a number of less expensive clinical indicators, already extensively used in schistosomiasis endemic areas, to predict morbidity. We provide recommendations based on analysis of data from 222 Zimbabwean schoolchildren in a crosssectional survey of S. haematobium associated pathology.

METHODS

From 1998-1999, 551 9-16 year old primary schoolchildren from the Chikwaka Communal Lands of Zimbabwe, an area endemic for S. haematobium,6,10,11 participated in this survey. Inclusion criteria comprised informed consent, minimum age of nine years with majority of the time spent in the immediate area, and no obvious indicator of ill health. During the preceding decade, no organized schistosomiasis treatment campaigns were conducted in the area.

Students were screened for Schistosoma mansoni and geohelminths using Kato-Katz thick smear method.¹² Additionally, 3 urine specimens per student, taken during the period for optimum egg excretion i.e. between 10:00 and 14:00 hrs on 3 different days, were examined for presence of S. haematobium. Eggs were visualized after staining with Lugol’s iodine¹³ A patient was considered infected if a 10 ml urine sample contained at least one egg. Reagent strips (Hemastix®, Bayer Diagnostics) were used on samples to determine the presence and extent of haematuria and proteinuria.

A subset of students (n= 222), from whom we had complete parasitological data, who were uninfected with S. mansoni, and who were present on the survey days, were examined using a portable ultrasound device (UF-5800A, Fukuda Denshi Co., with a 3.5 MHz convex probe). Thirty-three of these students were uninfected and served as endemic controls. Bladders were examined when full and the ultrasonographer was unaware of patient infection status. A transverse measurement of the bladder was taken and pathology was classified as 0-No pathology, wall < 5mm; no masses, or polyps; 1- Mild, wall < 5mm; Focal thickenings, no masses or polyps; or 2- Severe, wall ≥ 5mm; and/or masses or polyps.^6,14. Kidneys were examined post voiding and dilation initially classified as follows: 0- No dilation; 1- < 5 mm; 2- 5-15 mm; with > 2 cm parenchyma; 3- > 15 mm with £ 2 cm parenchyma; or end-stage with absence of parenchyma.¹⁴ Because one kidney can compensate for the other, for analysis we further categorised the data according to whether damage was uni- or bilateral: 0- No pathology; 1- Mild, one kidney with grade 1 pathology; the other, 0 or 1; 2- Moderate, one kidney, grade 2; the other, 0 or 1; 3- Severe, both kidneys, grade 2; or one kidney, grade 3.

To those who underwent ultrasound examination, a questionnaire was administered eliciting information on education, demographic information, type and duration of water contact activities, past or present occurrence of symptoms, and treatment history. Univariate analyses, an odds ratio or chi-square for trend, were used to examine which questionnaire items were associated with morbidity.⁶ Data analysis was performed using SPSS software (Version 10.0). For statistically significant indicators (two-sided Pvalues < 0.05), the sensitivity, specificity, and positive and negative predictive values were calculated. Combinations of clinical indicators were also compared. Results were stratified by gender when the gender-specific values varied more than –5 percentage points from the combined value.

All study methods were approved by the Medical Research Council of Zimbabwe and the Institutional Review Board of the Johns Hopkins Bloomberg School of Public Health. Infected participants were given a single oral dose of 40mg/kg praziquantel (Biltricide®, Bayer LTD) at the end of the investigation at their school.

RESULTS

Schistosoma haematobium infection was found in 329 of the 551 students surveyed (60%). In those who underwent ultrasound examination, morbidity was significantly linked with infection status (Table 1). Urinary tract pathology was present in 72% of those infected, with 49/184 (27%) having major wall thickenings of or masses or polyps on their bladder. Hydronephrosis was found in 67/188 (36%) of infected students, with 22% having bilateral dilations (Table 1). Dilation of the kidneys occurred alongside bladder pathology in 34/183 (19%) of cases. There was no correlation between presence or severity of bladder pathology and presence or extent of kidney pathology.

Fatigue and pain upon urination were more likely in patients with kidney pathology.⁶ Although not everyone with morbidity suffered such symptoms (low sensitivity), fatigue and dysuria were not common among those without hydronephrosis (high specificity) (Table 2). Therefore, kidney pathology should be suspected when S. haematobium infected children exhibit these symptoms.

While the values obtained in this investigation are specific to the population observed, they do suggest trends that are likely to apply on a wider basis. In our study population, proteinuria, high parasite egg counts, and macrohaematuria were more likely in those who developed bladder pathology. Pain upon urination and fatigue were more often reported in those with kidney pathology than those without. We were, however, unable to identify an ideal diagnostic with both high specificity and sensitivity. Although imperfect, such criteria may be useful in identifying children with urinary tract pathology when more technically complex means to assess morbidity cannot be performed. Our findings also underscore the need for further research on other diagnostic candidates that may improve identification of children with urinary tract pathology and thus allow better monitoring of progress towards the goal of reducing S. haematobium related morbidity.

ACKNOWLEDGEMENTS

We are thankful for the many efforts of the staff of the Blair Research Laboratory who facilitated collection and processing of parasitological samples. We are also very grateful to the Chikwaka District Health Office, Bosha Rural Health Centre, and Nyagui, Chipangura, and Mavhudzi schools for their cooperation with our surveys. Thanks are due to the Japan International Cooperation Agency for loaning us their ultrasound machine. This study was supported by the U.S. National Institutes of Health (Grant 1 RO3 DK53207-01 and NIAID Training Grant T32AI07417) and the J. William Fulbright Fellowship program.

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