National Schistosomiasis Control Programme Research Articles

Promotion of strategy transition for national schistosomiasis control programme by implementation of the regulation of schistosomiasis control in China

日本血吸虫病在我国流行历史悠久、危害严重.据建国初期统计,我国的血吸虫病分布在湖南、湖北、江西、安徽、江苏、四川、云南、浙江、广东、广西、福建、上海12个省(直辖市、自治区),共有钉螺面积148亿m2,病人数达1160万例之多,病牛120余万头.血吸虫病严重流行不仅危害了疫区人民的健康,也严重阻碍了社会经济发展.经过50年的积极防治,已有广东、上海、福建、广西、浙江5省(直辖市、自治区)消灭了血吸虫病.全国435个流行县中,已有264个县达到血吸虫病传播阻断标准,有66个县达到血吸虫病传播控制标准.目前尚未控制血吸虫病流行的地区主要集中在长江流域的湖南、湖北、江西、安徽、江苏五省的江湖洲滩地区和四川、云南两省的大山区.7省尚有105个县(市、区)尚未控制血吸虫病流行,血吸虫病病人80余万例,其中晚期血吸虫病人2.88万余例,受威胁人口约3800多万。

Bayesian spatial analysis and disease mapping: tools to enhance planning and implementation of a schistosomiasis control programme in Tanzania

To predict the spatial distributions of Schistosoma haematobium and S. mansoni infections to assist planning the implementation of mass distribution of praziquantel as part of an on-going national control programme in Tanzania. Bayesian geostatistical models were developed using parasitological data from 143 schools. In the S. haematobium models, although land surface temperature and rainfall were significant predictors of prevalence, they became non-significant when spatial correlation was taken into account. In the S. mansoni models, distance to water bodies and annual minimum temperature were significant predictors, even when adjusting for spatial correlation. Spatial correlation occurred over greater distances for S. haematobium than for S. mansoni. Uncertainties in predictions were examined to identify areas requiring further data collection before programme implementation. Bayesian geostatistical analysis is a powerful and statistically robust tool for identifying high prevalence areas in a heterogeneous and imperfectly known environment.

Applications and outcomes of periodic epidemiological surveys for schistosomiasis and related economic evaluation in the People's Republic of China

The great success in schistosomiasis control in China is attributable to a range of factors. Periodic epidemiological surveys (PES) used for monitoring and adapting control interventions over time are an integral feature of the national schistosomiasis control programme. PES have enabled the dynamic trends of schistosomiasis epidemics to be closely pursued and have assisted in analysing subtle changes in endemicity. The results can be summarised mathematically allowing the variation in efficacy of control measures to be readily determined and enabling control strategies to be adjusted and updated. PES have been used in both cross-sectional and longitudinal pilot studies selected by appropriate sampling methods. In the early 1990s, when the World Bank Loan Project for schistosomiasis control commenced, economic evaluations were initiated in parallel. Cost-effectiveness analysis became a necessary tool to identify the most financially feasible yet effective options among a range of alternative control strategies. There was, however, a lack of standardised approaches rendering study comparisons across sites difficult. The global burden of disease study established the disability adjusted life year (DALY) as a measure of population health, combining in a single indicator years lost from premature death and years of life lived with disability. However, a recent meta-analysis reveals that the burden of schistosomiasis is underestimated, and hence, needs to be revised. It is envisaged that after the revision of DALYs lost due to schistosomiasis japonica, they will become an essential measure in future schistosomiasis control assessments in China and in other schistosome-endemic areas of the world.

An economic evaluation of the national schistosomiasis control programme in China from 1992 to 2000

The World Bank Loan Project, by far the largest effort in China for schistosomiasis control since control activities were initiated in the mid 1950s, was carried out for a 9-year period commencing in 1992 in the 8 provinces where Schistosoma japonicum remained endemic when the project started. To evaluate its impact, a retrospective economic evaluation was done in 2001. Six representative counties, i.e. Huarong in Hunan province, Qianjiang in Hubei province, Yugan in Jiangxi province, Tongling in Anhui province, Xichang in Sichuan province and Dali in Yunnan province, were selected for the study. The total financial input in these counties from 1992 to 2000 was RMB Yuan 90.334 million with the World Bank loan accounting for 40.9%. Control efforts resulted in reduction of human prevalence rates in the six counties from 0.7–9.0% in 1992 to 0.1–2.7% in 2000. With regard to S. japonicum infection in bovines, a high reduction was observed in Qianjiang, and smaller decreases were noted in four counties, while there was an increase in Dali. In general, the areas infested by the intermediate host snail fluctuated around the initial level. The net benefit-cost ratio was 6.20, which means that this project gained US$ 6.20 for every dollar spent. The correlation coefficients of the net benefit-cost ratio to the human and bovine infection rates at the beginning of the project were 0.55 and 0.66, respectively. It is conceivable that further progress in schistosomiasis control is an important feature for sustained growth of the local economy, particularly in areas where control of the disease has been most challenging.

Immunodiagnosis and its role in schistosomiasis control in China: a review

Parasitological techniques (stool examination and/or urine filtration) are still the diagnosis of choice in national schistosomiasis control programmes the world over. However, the success of current control efforts, mainly due to the large-scale administration of praziquantel, emphasises the need for a more sensitive approach. In addition, microscopy is labour-intensive and time-consuming, while declining compliance rates after repeated chemotherapy make good coverage for the long-term increasingly problematic. China's success in the control of schistosomiasis is contributing to an enhanced understanding of the need for better and more sensitive screening methods. Immunodiagnostic techniques have a high sensitivity, are easy to perform and are an excellent epidemiological tool for the screening of target populations in schistosome-endemic areas. These assays are also useful for the surveillance of cure after chemotherapy, and for periodic control of transmission of the infection after it has been eliminated in an area. A succinct historical background of using immunodiagnosis for schistosomiasis japonica in China is given, together with a review and evaluation of the relative efficacy of the main techniques applied, i.e. the intradermal test, the circumoval precipitation test, the indirect hemagglutination assay, the dye dipstick immunoassay and different kinds of enzyme-linked immunosorbent assay applications. The important role of immunodiagnosis in the screening for schistosomiasis in China is discussed.

A geographic information and remote sensing based model for prediction of Oncomelania hupensis habitats in the Poyang Lake area, China

A model was developed using remote sensing and geographic information system technologies for habitat identification of Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum, in the Poyang Lake area, China. In a first step, two multi-temporal Landsat TM 5 satellite images, one from the wet and the second from the dry season, were visually classified into different land-use types. Next, the normalized difference vegetation index was extracted from the images and the tasseled-cap transformation was employed to derive the wetness feature. Our model predicted an estimated 709 km 2 of the marshlands in Poyang Lake as potential habitats for O. hupensis. Near-ground temperature measurements in April and August yielded a range of 22.8–24.2 °C, and pH values of 6.0–8.5 were derived from existing records. Both climatic features represent suitable breeding conditions for the snails. Preliminary validation of the model at 10 sites around Poyang Lake revealed an excellent accuracy for predicting the presence of O. hupensis. We used the predicted snail habitats as centroids and established buffer zones around them. Villages with an overall prevalence of S. japonicum below 3% were located more than 1200 m away from the centroids. Furthermore, a gradient of high-to-low prevalence was observed with increasing distance from the centroids. In conclusion, the model holds promise for identifying high risk areas of schistosomiasis japonica and may become an important tool for the ongoing national schistosomiasis control programme. The model is of particular relevance for schistosome-affected regions that lack accurate surveillance capabilities and are large enough to be detected at most commercially available remote sensing scales.

Use of praziquantel for clinical treatment and morbidity control of schistosomiasis japonica in China: a review of 30 years’ experience

Chemotherapy is widely acknowledged as the most important, rapid and cost-effective method of reducing morbidity due to schistosome infections. The discovery of praziquantel in the 1970s has been a breakthrough for treatment of patients infected with schistosomes, including Schistosoma japonicum in China, and entire communities at risk of schistosomiasis. Praziquantel is usually administered in a single oral dose and has no or only mild and transient side effects. The drug is highly efficacious against S. japonicum, both in patients with acute and chronic stages of the infection, among subjects with extensive hepatosplenic involvement, and in patients with other complicated diseases. The cost of praziquantel has been reduced significantly over the past years. Hence, praziquantel has become the backbone of the national schistosomiasis control programme in China and in other countries where the disease remains endemic, most notably in sub-Saharan Africa. Chemotherapy with praziquantel also plays a role in transmission control of schistosomiasis, although transmission interruption cannot be reached by chemotherapy alone. Here, I review 30 years’ of experiences gained with the use of praziquantel for clinical treatment and larger-scale control of schistosomiasis japonica in China.

The School Health Programme in Behera: an integrated helminth control programme at Governorate level in Egypt

School Health Programmes offer the opportunity to deliver public health interventions to a great number of beneficiaries at a relatively low cost and are seen with growing interest by policy makers in developing countries and the donors’ communities. In Egypt a pilot School Health Programme has been implemented for the past 6 years in Behera, the largest and most populous Governorate of the Nile Delta. The Programme integrated additional activities for the control of soil-transmitted helminthiasis, human fascioliasis and anaemia in the National Schistosomiasis Control Programme (NSCP), implemented in Egypt since 1988 by the Ministry of Health and Population (MoHP). To facilitate planning and direct actions, a strong monitoring system was also developed, that generated useful information for the schistosomiasis control programme. The practical steps adopted to develop the programme are presented and discussed. Results from three rounds of monitoring (2000, 2001, 2002) are analysed and compared with baseline data conducted in 1996, together with the cost of each activity. On the basis of the experience gained by the Behera School Health Programme a number of operational recommendations are formulated.

Diagnosis of schistosomiasis japonica in Chinese schoolchildren by administration of a questionnaire

This paper describes a rapid, simple, cost-effective questionnaire for screening school-aged children at risk for Asian schistosomiasis in China. Five hundred and thirty-two children, aged 8–14 years, were selected from 3 schools in an area moderately endemic for Schistosoma japonicum in Hunan province. The questionnaire, comprising 15 multiple-choice questions, was administered by teachers in order to collect both ethnographic and epidemiological data relevant to current S. japonicum infections. This was followed by Kato-Katz thick smear stool examinations, miracidium hatching tests, and soluble egg antigen-enzyme linked immunosorbent assays in order to validate the efficacy of the questionnaire approach. The results from a combination of all 3 procedures indicated that the overall schistosomiasis prevalence in the 3 schools was 29·9% ( 138 472 ). Six risk factors (episodes of diarrhoea, frequency of water contact, school grade attained, weakness, past history of S. japonicum infection(s), and whether a subject had been previously treated for schistosomiasis) in the questionnaire were determined by logistic regression to be highly statistically significant predictors of individual current infection. The sensitivity (93·7%), specificity (91·9%) and low cost ( c. US$ 0·6/true positive case) associated with the 6 variables model make the questionnaire approach a very useful diagnostic tool for screening marshland and lake communities at high risk for schistosomiasis in China before selective treatment with praziquantel or diagnostic follow-up. An even simpler 3 variables ‘yes/no’ model was derived from the questionnaire and found to be nearly as good at predicting individual infection (sensitivity 86·2% and specificity exceeding 97·6%) and extremely simple to use. If validated in other ecological settings in China the questionnaire, modified or as presented here, could be adopted by the national schistosomiasis control programme.

Who misses out with school-based health programmes? A study of schistosomiasis control in Egypt

There has been a recent revival of interest in school-based health programmes in developing countries as a means of reducing the morbidity observed in school-aged children, of improving their physical growth and cognitive development, and of controlling transmission of disease in the community at large. This study used data collected from a large epidemiological survey of schistosomiasis in Egypt to examine what proportion of infected children missed treatment from an established national school-based schistosomiasis control programme simply because they did not attend school. It showed that children who were not enrolled in school had a higher prevalence of infection and were more intensely infected than children who attended school. At the extreme, over 80% of infected girls in one part of Egypt could not be treated by the existing school programme because they did not attend school. If these trends are similar in other countries where school-based programmes are being developed, school-based delivery may exacerbate existing inequalities in society and ways of expanding services to children who do not attend school regularly need to be explored.

A review of achievements of the national schistosomiasis control program in middle and upper Egypt areas.

In Egypt the "national schistosomiasis control program" was formulated to control transmission by reduction of prevalence and intensity of current infections, and thereby achieve an acceptable level of schistosomiasis disease control. The program was implemented foremost in Middle Egypt (1977) and Upper Egypt (1980), collectively extending 800 km alongside of the River Nile and accommodate about 10.5 million people. Schistosoma haematobium has been essentially the prevailing species infection in both areas. The strategy of control entailed both area-wide mollusciciding with niclosamide, and selective population chemotherapy with metrifonate. Evaluation in 1986 showed that prevalence dropped from pre-control 29.4% in Middle Egypt and 26.3% in Upper Egypt to 6% and 7.8% respectively, together with a remarkable drop of infections among children. Also mean intensity attained low levels consistent of low grade infections. It is evident therefore that in these areas where an enhancement of schistosomiasis infections had been anticipated the employment of the twofold strategy effected a state of low-prevalence/low-intensity signifying a lowered reservoir of infection and a substantial interference with the potentials of transmission.

Coping with intestinal illness among the Kamba in Machakos, Kenya, and aspects of schistosomiasis control

In a hyperendemic schistosomiasis mansoni area in Machakos District, Kenya, the Kamba use modern and traditional health services interchangeably with similar results. Schistosomiasis oral drug therapy administered through the Schistosomiasis Research Project reportedly achieved significantly higher cure rates than hospital and health center treatment, which in turn was not more effective than traditional medicine. Kamba knowledge and perceptions of the causes of intestinal illness, several types of preventive behavior, the role of women as health promoters, development of community water supplies and the utilization of plant molluscicides are briefly evaluated for possible use in the planned national schistosomiasis control program.