Evolution of Schistosoma haematobium-related pathology over 24 months after treatment with praziquantel among school children in southeastern Tanzania.

Little is known about the dynamics of pathology due to schistosomiasis following treatment. Public health authorities in endemic areas require such information to decide on the timing of treatment and re-treatment schedules. A study to assess the rate of clearance and reappearance of pathologic lesions due to Schistosoma haematobium using ultrasound has now been carried out in two schools in southeastern Tanzania, an area of moderate-to-high transmission. Baseline data collection found urinary tract pathology in 67% of 533 children. Lesions of the bladder were significantly associated with egg positivity and microhematuria. The attributable fraction estimate of major bladder lesions due to S. haematobium was 75%. In a cohort study, 224 infected children were examined by ultrasound and then treated with a standard dose of 40 mg of praziquantel/kg of body weight. They were re-examined at two, four, six, 12, 18, and 24 months after treatment. Before treatment, 76% had pathologic lesions of the urinary tract. The proportion showing lesions decreased sharply during the first months after treatment to 11% at six months. At 24 months, lesions were detected in 57%, and 11% had developed new severe pathology. In 18 cases, pathology was present throughout, and 34 did not show any pathology throughout the study. This study provides the first detailed report on the evolution of urinary tract pathology due to S. haematobium infections at the community level. The results will help in making decisions on treatment and re-treatment schedules and more generally will provide a basis for designing control strategies in areas of moderate-to-high transmission.

The use of morbidity questionnaires to identify communities with high prevalences of schistosome or geohelminth infections in Tanzania.

Parasitic infections were investigated in Morogoro Rural District, Tanzania, between October 1992 and June 1993. A total of 4589 schoolchildren (aged 7-17 years) from 30 primary schools was screened for infection with Ascaris lumbricoides, Trichuris trichiura, hookworms (3456 children only), Schistosoma mansoni and S. haematobium. The children were also asked about their recent experiences of the following: diarrhoea, abdominal pain, blood in stool, perception of suffering from schistosomiasis, and worm infection and examined for spleen and liver enlargement. Among schools, there were correlations between the prevalence of S. mansoni infection and bloody stools, spleen enlargement and liver enlargement, and between S. haematobium infection and the presence of blood in urine. To exclude ecological explanations for the correlations, logistic regression was used to estimate the adjusted odds ratio (OR) for each infection and each sign or symptom. No sign or symptom was significantly associated with any geohelminth infection. Reported blood in stool was significantly associated with S. mansoni infection (OR = 1.62, P = 0.045). Reported blood in urine was significantly associated with S. haematobium infection (OR = 7.71, P < 0.001), as was reported blood in stool (OR = 11.52, P < 0.001), indicating that presence of blood in either form of excreta was related to the local term for schistosomiasis. These results support the possibility of using reported blood in stool as a means of rapid assessment for identifying communities with a high prevalence of S. mansoni infection.

The population biology and epidemiology of schistosome and geohelminth infections among schoolchildren in Tanzania.

A study of helminth infections was undertaken among 3244 schoolchildren from 28 schools in Morogoro Rural District, Tanzania. Schistosoma haematobium was the most common infection, followed by hookworms, Ascaris lumbricoides, S. mansoni, and Trichuris trichiura. Infection prevalence of each species varied among schools and age groups, but not between sexes. There was no relationship between the prevalences of different infections among schools, except for a strong negative correlation between the prevalence of hookworm and S. mansoni infections. Within each age group, there was little excess overlap in the distribution of each infection; thus the number of multiple infections was low whereas the number of individuals harbouring at least one infection was relatively high. More children than expected carried infections of A. lumbricoides and S. mansoni, and the clustering effect increased with age. Only 2 schools had high overall infection prevalences of both geohelminths and schistosomes. Logistic regression analysis of morbidity and parasitological data indicated that individuals with multiple species infections were not at increased risk of morbidity (on a multiplicative scale) compared to individuals with single species infections. This was attributed in part to the low egg counts observed for each parasite species. The results implied little interaction between schistosome and geohelminth infections in the region, both in parasitological terms and in the context of their combined effects on health. Implications for the feasibility and benefits of combined control of geohelminths and schistosomes are discussed.

Evaluation of chemical and physical-morphological factors as potential determinants of Biomphalaria pfeifferi (Krauss, 1848) distribution.

This study was carried out in five sites along a small perennial river system in south-central Tanzania, which had been identified as the focus for transmission of intestinal schistosomiasis in the area. Malacological surveys preceding the study showed a focal distribution of Biomphalaria pfeifferi, intermediate host snail of Schistosoma mansoni, the snails being present in three sites but absent from the other two sites. The objective of this study was to evaluate to what extent chemical and/or physical-morphological factors determine the distribution of B. pfeifferi between these five sites. It was found that none of the chemical constituents in the waters examined were outside the tolerance range of B. pfeifferi snails. Moreover, the composition of water from B. pfeifferi-free sites was not different from that in those sites where snails occurred. Furthermore, none of the physical-morphological constituents seemed likely to be a determinant for the absence of B. pfeifferi. In view of these findings, and those of previous studies, it is concluded that the focal distribution of B. pfeifferi cannot be associated with a single environmental factor and is rather the result of more complex interactions of habitat factors.

Validation of reagent sticks in diagnosing urinary schistosomiasis in an urban setting.

In view of the established potential of reagent sticks for detecting haematuria, a pilot survey to validate their use in the diagnosis of urinary schistosomiasis in an urban setting was done at Kinyerezi primary school of Ilala district in Dar es salaam. From 404 pupils screened for the disease, 273 were positive for the eggs by microscopy (filtration method), giving a prevalence of 67.6% and 253 (92.6%) of those who were positive by microscopy were also positive for haematuria by reagent sticks. Out of 131 who had no disease, 113 (86.2%) were negative for haematuria by the reagent sticks. These findings indicate a high sensitivity and specificity of microhaematuria by the reagent sticks (92.6% and 86.2%) respectively. Taking microscopy as a standard test, macrohaematuria had a sensitivity and specificity of 40.6% and 90% respectively, for urinary schistosomiasis. The accuracy of microhaematuria by reagent sticks was 90% compared to macrohaematuria which was only 56.6%. The use of reagent sticks test in detecting microhaematuria is thus recommended as a valid and rapid diagnostic test for urinary schistosomiasis in the present setting.

Community-based questionnaires and health statistics as tools for the cost-efficient identification of communities at risk of urinary schistosomiasis.

Self-administered questionnaires, distributed by existing administrative channels to village party chairmen, head-teachers and schoolchildren, showed good diagnostic performance for the qualitative assessment of urinary schistosomiasis endemicity. At a cost 34 times below that of the WHO-recommended parasitological screening strategy, the schoolchildren's questionnaire allowed the screening of 75 out of 77 schools of a rural Tanzanian district in six weeks, and the exclusion of schools not at high risk for urinary schistosomiasis with over 90% confidence. The headteacher and party questionnaires made it possible to assess the perceived importance of a spectrum of diseases and symptoms, among which was schistosomiasis. The priority rank of schistosomiasis control was strongly correlated with the prevalence rate of the disease in the community. The questionnaires also looked for the prioritization of health among other community issues and thus contributed important information for planning at district level. Standardized monthly disease reports, sent by all primary health services, were also analysed. They allowed a zonal schistosomiasis endemicity classification.

Training of village health workers in Tanzania; a comparison of two approaches.

The paper compares the costs of training for two groups of Village Health Workers (VHWs) in Tanzania, where the policy of developing a system based on Primary Health Care principles will require the training of more than 16,000 VHWs during the next decade. In the Kilombero District, one group of VHWs was trained according to the guidelines of the National Programme of the Ministry of Health, and another group followed the training programme of the Kilombero Project, based on the Swiss Tropical Institute Field Laboratory. The training scheme of the Kilombero project cost almost 80% less for one VHW, largely because it depended on on-the-spot training by local staff. The results of a first investigation of the efficacy of the training were encouraging; a long-term evaluation is in progress. The curricula for the two programmes also differed; the Kilombero programme had shorter blocks of theory, interspersed with supervised practical work, and introduced curative medicine earlier in the course. The advantage and disadvantages of the two programmes are discussed, not only in terms of cost but also in terms of their efficacy in training VHWs who will be motivated, efficient and accepted by the community.

Ultrasound scanning for detecting morbidity due to Schistosoma haematobium and its resolution following treatment with different doses of praziquantel.

A study to assess the resolution of urinary tract morbidity due to Schistosoma haematobium was conducted on 2 cohorts of schoolchildren attending neighbouring schools in Kilombero District, southern Tanzania. Schoolchildren were screened for S. haematobium infection using the standard World Health Organization filtration technique and subsequently examined for urinary tract pathology using a portable 3.0 MHz sector scanner (Siemens Sonoline 1300). Treatment with praziquantel was given to all infected children. Children with observed urinary tract pathology received either 20 (n = 52) or 40 (n = 79) mg/kg body weight and were sonographically re-examined one, 2, 3 and 6 months following treatment. Geometric mean outputs of 21 and 19 eggs/ml of urine were detected in the 2 cohorts before treatment. Urinary tract pathology correlated positively with egg output (chi 2, P = 0.02) and microhaematuria (P = 0.0001). Bladder (wall irregularities and polyps) and kidney (congestive changes) pathologies were found in 81% and 36%, respectively, of the group that received 20 mg/kg of praziquantel, and in 78% and 46% of the group that received 40 mg/kg. Six months after treatment, 90.4% and 88.0% parasitological cure rates were obtained using 20 or 40 mg praziquantel/kg body weight. The respective pathology clearances were 88% and 91%. 20 mg/kg of praziquantel was as effective with regard to cure rates and reversibility of morbidity as 40 mg/kg.

Measurement of schistosomiasis-related morbidity at community level in areas of different endemicity.

Among the indicators of schistosomiasis morbidity currently used in control programmes, ultrasound has been found to be a safe, non-invasive and efficient technique for detecting schistosomiasis-related lesions and for assessing the effect of treatment on their resolution. Three case-studies from East Africa, in areas of different endemicity for Schistosoma haematobium, using ultrasound are described and their results related to indirect measurements of the disease (e.g., haematuria, egg counts). This review reveals that cross-sectional ultrasound surveys can be used to quickly assess subsamples of populations in areas of different endemicity, in order to make decisions about sampling strategies in control programmes. The association between the intensity of infection and urinary tract abnormalities is reviewed and evaluated. One case study provides information on the resolution of S. haematobium-related uropathy after treatment; this information is crucial in order to maintain low levels of morbidity in a community. The role of ultrasound is further discussed, particularly as a tool to complement and validate indirect morbidity control measurements. The validation of such indirect measurements for use as a basis for public health decisions is important because they can be carried out by existing health care services in many areas.

Longitudinal study on the health status of children in Kikwawila village, Tanzania: study area and design.

The paper describes the study area and the project design of a longitudinal study on the health status of children undertaken in Kikwawila village in southeastern Tanzania from 1982 to 1984. This rural village is situated in the Kilombero river plain (270 m above sea level) and extends over 50 km2. A census in 1982 (repeated in 1984) revealed that 1152 (1406) people lived in 260 (299) households of the nucleated roadside settlements of the sectors Kikwawila and Kapolo. The vital statistics showed an infant mortality rate estimate of 198/1000 which was far above the regional (140%) and the national (137%) averages. Over 30 tribes were recorded but 6 tribes formed 84% of the population. The population was predominantly muslim (75%). Most adult inhabitants (90%) were subsistence farmers cultivating an average of 3.7 acres per household. Rice, maize and cassava were the main crops of the area. At the beginning of the study, the village had no village health post, dispensary or health centre and it lacked an adequate and safe water supply. A great proportion of the population (67%) had to rely on water from unprotected hand dug wells and from rivers for domestic purposes. Only half of the households had a simple pit latrine. Even when latrines were present, they collapsed after heavy rains due to loose, unconsolidated soils, termites and the high water table. These difficulties affected the sustained success of sanitation campaigns. The study area represented a typical settlement of the Kilombero valley and was, with regard to most demographic, ethnic, agricultural and health characteristics, considered a suitable pilot area. A primary health care programme based on village health workers was implemented in parallel with complementary community based studies on the causes, interrelations and control measures of the major health problems faced by the community, and possible control measures.

Longitudinal study on the health status of children in a rural Tanzanian community: parasitoses and nutrition following control measures against intestinal parasites.

Three repeated cross-sectional surveys were undertaken among children (1 month to 15 years) of a rural community in southeastern Tanzania. The study was part of a longitudinal project on the interactions among nutrition, parasitic infections and immunity within a primary health care programme emphasizing village health workers. All children underwent interviews and parasitological, anthropometric, anamnestic and clinical examinations. Out of 550-590 children examined each year, a cohort of 170 children could be followed for three consecutive years. Malaria was holo- to hyperendemic in the community, P. falciparum accounting for greater than 90% of the infections. The parasite and spleen rates were 88% and 67%, respectively, and the average enlarged spleen index was 2.0 among children from 2-9 years in 1982. Transmission of malaria was high and stable as indicated by a parasite rate of 80% among infants between 1 month and 1 year during the whole period of study. G. lamblia, hookworm (N. americanus), Strongyloides spp. and Schistosoma haematobium were highly prevalent and annual incidence rates were high, while Entamoeba histolytica, Ascaris and Trichuris were of minor importance. Prevalence and incidence of parasitic infections did not differ by sex. Multiparasitism was very frequent and less than 11% of all children were parasite-free in each year. Not a single child remained parasite-free for three consecutive years. An anthropometric assessment showed a high degree of stunting (35-71%) and a substantial proportion of wasting (3-20%). The growth potential was normal in girls and boys during the whole period of study. There were indications that malaria was the main contributory factor to growth retardation among young children. Hookworm infection did not significantly affect the packed-cell volume of the children, probably owing to the low intensity of infection. Due to the multiparasitism and the lack of parasite-free individuals, single-parasite and single-nutrient effects were difficult to unravel. A latrine campaign followed by a single mass treatment against hookworm (single oral dose of albendazole, 400 mg) and/or G. lamblia (single oral dose of ornidazole, 40 mg/kg) only temporarily affected the prevalence and incidence of G. lamblia, and only resulted in a decrease in the intensity of hookworm infections up to six months after the interventions. As the effects of the latrine campaign and a single mass treatment on the parasite load were only transient, no sustained impact on nutritional variables was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Longitudinal study on the health status of children in a rural Tanzanian community: comparison of community-based clinical examinations, the diseases seen at village health posts and the perception of health problems by the population.

Standardised household interviews among adults and children, open-ended questionnaires, and clinical examinations administered during cross-sectional health status surveys, as well as the registers of village health posts (VHP), were used to assess the pattern of health problems of a rural community in southeastern Tanzania, and their results compared. All four approaches gave very similar results for the two major health problems (fever/malaria and abdominal pain or discomfort) which were mentioned by both children and adults. The parasitological data from the cross-sectional surveys also revealed hyperendemic P. falciparum malaria and a high prevalence and incidence for infections with hookworm (N. americanus), Strongyloides, and G. lamblia. However besides consistently revealing the two major health problems, each approach showed a distinct pattern for the additional health problems: household interviews and open-ended questionnaires resulted in a higher ranking of problems that had not yet been solved by the health care facilities available in the community at the time of the interview. This view was further biased by the fact that the interviews were done by people representing the health professionals. The statistics from the registers of VHP clearly reflected the types of treatment provided by this service. Malnutrition and various eye problems only became evident during the clinical examination of the population. However, the clinical examination did not identify the importance of the abdominal problems in the community. The cross-sectional survey (questionnaires, clinical examination) chiefly showed the health problems affecting the population around the time of the surveys (end of the dry season). Interestingly, the registers of the VHP did not show marked seasonal variations in the morbidity statistics for this community. Both questionnaire approaches and the registers of VHP showed a change in both the morbidity and the disease perception pattern that may reflect the effects of interventions launched at community level (activities of village health workers, mass-treatment against hookworm and G. lamblia). The study indicated that the individual ranking of the major health problems matched with data from health status surveys. It also pointed to the possibility that disease perception patterns could become a tool for community diagnosis and for the monitoring of health care programs.