Long-term suppression of adult bladder morbidity and severe hydronephrosis following selective population chemotherapy for Schistosoma haematobium.
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Repeated selective population chemotherapy of school age children reduces infection and morbidity associated with Schistosoma haematobium infection. To examine the long-term effect of this treatment on susceptibility to re-infection and late disease, a cohort of Kenyans (n = 194) were re-examined for infection and urinary tract morbidity 7-13 years after they underwent annual ultrasonography and treatment for an average of 5 years beginning in 1984 as children. Controls were previously untreated age-matched individuals residing in the same or adjacent villages. The overall prevalence and intensity of infection were equivalent between the 2 groups. In contrast, the prevalence of bladder wall pathology was 11-fold lower in previously treated (1.5%) versus untreated subjects (17%). Severe hydronephrosis was completely reversed. These data demonstrate that treatment significantly reduced urinary tract morbidity despite re-infection, and suggest that the important risk factors for urinary tract morbidity in adulthood are cumulative intensity and duration of infection during early adolescence. (+info)
The epidemiology of a recent focus of mixed Schistosoma haematobium and Schistosoma mansoni infections around the 'Lac de Guiers' in the Senegal River Basin, Senegal.
(10/301)
A village with mixed Schistosoma mansoni and S. haematobium infections (probably in a early endemic phase) was identified around the Lac de Guiers in the Senegal River Basin. In documenting the epidemiology of both schistosomes, we focused on prevalence and intensity of infection, transmission patterns and the impact of treatment. S. mansoni prevalences (near 100%) and egg counts (overall geometric mean eggs per gram of faeces (epg) of 589 were high in all age groups, with 35% of individuals excreting > 1000 epg, and showing a slow decline in egg output only after the age of 30 years. The overall prevalence (28%) and egg counts (2% > 50 eggs/10 ml) of S. haematobium were low, with mean counts of 6.3 eggs/10 ml. Maximal mean S. mansoni egg counts were found in 5-9 year-old boys and in 15-19 year-old girls; S. haematobium maximal counts in 1-4 year-old boys and in girls aged 5-9. Extremely high Biomphalaria pfeifferi infection ratios were recorded over the whole year. Following a single treatment, re-infection was rapid with prevalences and mean egg counts of both Schistosoma species reaching pretreatment levels within 7 months. (+info)
Developing strategies to control schistosomiasis morbidity in nonenrolled school-age children: experience from Egypt.
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Schistosomiasis is a major health problem in school-age children in much of the tropical world. They harbour the most intense infections for both Schistosoma mansoni and S. haematobium. In Egypt, the Ministry of Health and Population (MOHP) has implemented a successful school-based treatment programme in which children are screened and those found to be infected treated with praziquantel. High nonenrolment rates in some rural areas have a negative impact on the coverage of this programme and on its ability to reduce transmission in the community. The main aim of our study was to introduce and test a simple intervention to extend treatment to nonenrolled children using the routine MOHP schistosomiasis treatment programme. Twenty villages or ezbas in Tamia district, Fayoum governorate, with 8 schools and 1901 nonenrolled children were targeted. 88.5% of nonenrolled children attended schools to avail themselves of treatment. Coverage rates were significantly higher for girls (P < 0.001). These results are important for countries where schistosomiasis is endemic. They suggest that offering interventions in schools may not only improve the health of school attendees but also be an affordable way of extending services to out-of-school children. (+info)
Impact of the crayfish Procambarus clarkii on Schistosoma haematobium transmission in Kenya.
(12/301)
The Louisiana red swamp crayfish, Procambarus clarkii, which was introduced into east Africa in the 1950s or 1960s, has since widely dispersed. Previous work by our group has shown that P. clarkii can reduce populations of the molluscan intermediate hosts of human schistosomes through predatory and competitive interactions. Here, we investigate whether crayfish can reduce populations of Bulinus africanus and consequently, Schistosoma haematobium prevalence in school children. Children from 6 primary schools in the Machakos and Kitui Districts of Kenya were selected for study. Schools were divided into 3 experimental-control pairs. At experimental schools, crayfish were introduced into nearby aquatic habitats harboring Bulinus africanus snails and serving as S. haematobium transmission sites. Snail habitats near control schools did not receive crayfish. Six months after crayfish introduction, all infected children were treated with praziquantel. Children were then monitored quarterly for 2 years, at which time infection and reinfection rates were compared statistically between the paired schools. In one such pair, crayfish failed to establish, resulting in neither snail control nor a reduction in transmission. At the second pair of schools, the numbers of snails were decreased by the presence of crayfish, but a clear difference in infection rates in children could not be detected, primarily because drought conditions kept overall transmission rates low. At the third school pair, crayfish established well in experimental habitats, snail numbers decreased precipitously, and children at the experimental school were significantly less likely to acquire S. haematobium infections than children at the control school. Our results indicate that under certain environmental circumstances, P. clarkii exerts a significant impact on the transmission of human schistosomiasis in Kenya. Important questions remain regarding the impact of P. clarkii on Kenyan freshwater ecosystems, not the least of which is its potential to significantly influence the epidemiology of schistosomiasis in east Africa. (+info)
The impact of population level deworming on the haemoglobin levels of schoolchildren in Tanga, Tanzania.
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The impact of albendazole (400 mg) and praziquantel (40 mg/kg body weight) treatment of schoolchildren was compared with placebo according to the presence of anaemia (haemoglobin concentration < 11. 0 g/dl) and heavy (> 5000 epg) or light (< 5000 epg) hookworm egg load. The study was conducted in rural Tanga. Medication was administered in September 1994 and children were followed-up in January 1995. Overall, anthelminthic treatment reduced the fall in haemoglobin concentration compared with that observed in the placebo group (- 0.11 g/dl vs. - 0.35 g/dl; P = 0.02). Anthelminthic treatment was of greatest benefit to the 9% of children with both anaemia and heavy hookworm egg load (+ 0.67 g/dl vs. - 0.67 g/dl) and was also of significant benefit to the 38% of children with anaemia and light hookworm egg load (+ 0.07 g/dl vs. - 0.21 g/dl). It was of no significant benefit to children who were not anaemic. This study suggests that single-dose anthelminthic treatment distributed in schools in this area achieves haematological benefits in nearly half of children infected with S. haematobium and geohelminths (37% of total population). (+info)
The performance of school-based questionnaires of reported blood in urine in diagnosing Schistosoma haematobium infection: patterns by age and sex.
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This study investigates the performance of school-based questionnaires of reported blood in urine as an indicator of the prevalence of Schistosoma haematobium infection in schools and the presence of infection in individuals. In most schools (87%), the prevalence of reported blood in urine underestimates the prevalence of S. haematobium infection. Predictive value analysis suggests that a threshold of 30% reported blood in urine would identify most of the high prevalence schools (i.e. those with 50% or more children infected with S. haematobium). Although the prevalence of S. haematobium infection was greater in males than females, girls reported a lower prevalence of blood in urine than boys even at comparable levels of infection. Reported blood in urine in females was more specific (identifying 10% more uninfected girls than the sign in boys), but was far less sensitive (identifying less than 20% of infected girls than boys). The sensitivity of reported blood in urine was also related to age, being significantly lower in girls over 14 years of age. The proportion of infected children who reported blood in urine was also lower in schools where the prevalence of reported blood in urine is less than 30%. The results suggest that the selective treatment of children based on reported blood in urine in low prevalence schools would miss a high proportion of infected children, particularly girls. It remains unclear whether other rapid assessment techniques, such as the use of reagent strips, would offer greater cost-effectiveness. (+info)
Acute pulmonary schistosomiasis in travelers returning from Lake Malawi, sub-Saharan Africa.
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We describe four cases of acute schistosomiasis presenting to the Infectious Diseases Unit of John Radcliffe Hospital (Oxford, England) during a 2-month period in autumn 1997. All four patients had swum in Lake Malawi, a freshwater lake in sub-Saharan Africa that is associated with Schistosoma haematobium and, less commonly, Schistosoma mansoni infections. All four patients had a severe acute illness and had prominent pulmonary involvement, both clinically and radiologically. This represents a change in the recognized pattern of presentation and could possibly reflect a new parasite variant in the lake. (+info)
Control of urinary schistosomiasis: an investigation into the effective use of questionnaires to identify high-risk communities and individuals in Niger State, Nigeria.
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Schistosomiasis is a public health problem in Nigeria. Although there is a national programme for its control, there is the need for reliable and simple means of rapidly diagnosing communities to provide a detailed map on the distribution of the disease in the country, in order to prioritize control activities, as well as to monitor the effectiveness of control operations. A rapid assessment technique using school questionnaires was tested in Borgu Local Government Area (LGA), Niger State, north-western Nigeria. Following a series of focus group discussions, the questionnaires were adapted before they were administered through the school system to 60 primary schools in Borgu LGA. Correctly completed questionnaires were returned from 58 schools (97%) within 4 weeks. Questionnaires were validated by reagent stick tests performed by trained teachers. Their results proved to be reliable compared to those obtained by our research team in 20 randomly selected schools. Overall prevalences of microhaematuria at 1+ and 2+ levels were 45.7% and 27. 1%, respectively. Highly significant correlations were obtained between school prevalence of microhaematuria and reported schistosomiasis, as well as reported blood in urine. The diagnostic performance of the questionnaires at the 2+ level of microhaematuria was very good. The design of our study also allowed data analysis on an individual level, and multivariate analysis revealed highly significant odds ratios for reported schistosomiasis and reported blood in urine to detect an individual with urinary schistosomiasis. Our results are in good agreement with reports from other African countries, and questionnaires can be recommended for rapid identification of communities at highest risk of urinary schistosomiasis in Nigeria, so that scarce resources of the national control programme can be used most effectively. (+info)