Measuring exposure to Schistosoma japonicum in China. III. Activity diaries, snail and human infection, transmission ecology and options for control

Li, Yuesheng; Sleigh, Adrian; Williams, Gail M.; Ross, Allen G.; Li, Y.; Forsyth, Simon; Tanner, Marcel; McManus, Donald P.

doi:10.1016/s0001-706x(00)00056-5

Cited by 26 publications

(22 citation statements)

References 23 publications

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“…Although the risk factors (61,119,166,223) and means of becoming infected (i.e., occupation [fishing and farming], domestic duties [washing], and social activities [swimming]) are likely similar in the areas of endemicity around both Poyang and Dongting Lakes, there are subtle differences in the patterns of transmission. The areas of endemicity in the Poyang Lake region have two distinct transmission seasons.…”

Section: Transmission Patternsmentioning

confidence: 99%

Schistosomiasis in the People's Republic of China: the Era of the Three Gorges Dam

et al. 2010

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SUMMARY The potential impact of the Three Gorges Dam (TGD) on schistosomiasis transmission in China has invoked considerable global concern. The TGD will result in changes in the water level and silt deposition downstream, favoring the reproduction of Oncomelania snails. Combined with blockages of the Yangtze River's tributaries, these changes will increase the schistosomiasis transmission season within the marshlands along the middle and lower reaches of the Yangtze River. The changing schistosome transmission dynamics necessitate a comprehensive strategy to control schistosomiasis. This review discusses aspects of the epidemiology and transmission of Schistosoma japonicum in China and considers the pathology, clinical outcomes, diagnosis, treatment, immunobiology, and genetics of schistosomiasis japonica together with an overview of current progress in vaccine development, all of which will have an impact on future control efforts. The use of synchronous praziquantel (PZQ) chemotherapy for humans and domestic animals is only temporarily effective, as schistosome reinfection occurs rapidly. Drug delivery requires a substantial infrastructure to regularly cover all parts of an area of endemicity. This makes chemotherapy expensive and, as compliance is often low, a less than satisfactory control option. There is increasing disquiet about the possibility that PZQ-resistant schistosomes will develop. Consequently, as mathematical modeling predicts, vaccine strategies represent an essential component in the future control of schistosomiasis in China. With the inclusion of focal mollusciciding, improvements in sanitation, and health education into the control scenario, China's target of reducing the level of schistosome infection to less than 1% by 2015 may be achievable.

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Section: Transmission Patternsmentioning

confidence: 99%

Schistosomiasis in the People's Republic of China: the Era of the Three Gorges Dam

et al. 2010

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“…8 Transmission to humans requires that they come in contact with fresh water colonized by amphibian snail hosts (Oncomelania hupensis quadrasi) that have become infected with S. japonicum through contamination by faeces from infected mammals. 9 Pigs, dogs, cats, rats, cows and water buffalo may become infected and may potentially play a role in the transmission of S. japonicum to humans, 6,10,11 but the association between infection levels in animals and humans has not yet been estimated.…”

Section: Cross-sectional Associations Between Intensity Of Animal Andmentioning

confidence: 99%

Cross-sectional associations between intensity of animal and human infection with Schistosoma japonicum in Western Samar province, Philippines

McGarvey

Carabin

Balolong

et al. 2006

Bull World Health Organ

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Objective To estimate the association between the intensity of animal infection with Schistosoma japonicum and human infection in Western Samar province, the Philippines. Methods We conducted an observational cross-sectional study of 1425 households in 50 villages. Stool samples were collected on each of 1-3 days from 5623 humans, 1275 cats, 1189 dogs, 1899 pigs, 663 rats and 873 water buffalo. Intensity of infection with S. japonicum was measured by the number of eggs per gram (EPG). Egg counts were done using the Kato-Katz method. We used a Bayesian hierarchical cumulative logit model, with adjustments for age, sex, occupation and measurement error. Findings The adjusted proportions of humans lightly infected (classified as 1-100 EPG) was 17.7% (95% Bayesian credible interval = 15.3-20.2%); the proportion classified as at least moderately infected (>100 EPG) was 3.2% (2.2-4.6%). The crude parasitological results for animals indicated that 37 cats (2.9%), 228 dogs (19.2%), 39 pigs (2.1%), 199 rats (30.0%) and 28 water buffalo (3.2%) were infected. In univariate analyses the odds ratios corresponding to a unit increase in the mean number of EPG at the village-level in dogs was 1.05 (1.01-1.09), in cats 1.35 (1.02-1.78), in pigs 1. 16 (0.24-5.18) and in rats 1.00 (1.00-1.01). Mean EPG values in cats, dogs, pigs and rats were correlated with one another. This confounding made interpreting the odds ratios difficult, but the odds ratios for dogs and cats were more consistent. Conclusion S. japonicum is endemic in areas of the Philippines despite implementation of control programmes. This may be due to the association of infections in dogs and cats with human infections. Infection control in dogs and cats is challenging, and there is a need to develop new methods to control transmission across all species. Voir page 450 le résumé en français. En la página 450 figura un resumen en español.

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“…For example, clusters of Schistosoma hematobium infections in rural Kenya were identified near water bodies with high numbers of cercaria-shedding snails [5]. Also, in contrast to water contact measures that ignore spatial variability in cercarial density, measures of water contact that adjust for estimated cercarial density at the site of contact have shown strong correlations with human infection intensity [6,7]. …”

Section: Introductionmentioning

confidence: 99%

Using variable importance measures from causal inference to rank risk factors of schistosomiasis infection in a rural setting in China

Sudat

Carlton

Seto

et al. 2010

Epidemiol Perspect Innov

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BackgroundSchistosomiasis infection, contracted through contact with contaminated water, is a global public health concern. In this paper we analyze data from a retrospective study reporting water contact and schistosomiasis infection status among 1011 individuals in rural China. We present semi-parametric methods for identifying risk factors through a comparison of three analysis approaches: a prediction-focused machine learning algorithm, a simple main-effects multivariable regression, and a semi-parametric variable importance (VI) estimate inspired by a causal population intervention parameter.ResultsThe multivariable regression found only tool washing to be associated with the outcome, with a relative risk of 1.03 and a 95% confidence interval (CI) of 1.01-1.05. Three types of water contact were found to be associated with the outcome in the semi-parametric VI analysis: July water contact (VI estimate 0.16, 95% CI 0.11-0.22), water contact from tool washing (VI estimate 0.88, 95% CI 0.80-0.97), and water contact from rice planting (VI estimate 0.71, 95% CI 0.53-0.96). The July VI result, in particular, indicated a strong association with infection status - its causal interpretation implies that eliminating water contact in July would reduce the prevalence of schistosomiasis in our study population by 84%, or from 0.3 to 0.05 (95% CI 78%-89%).ConclusionsThe July VI estimate suggests possible within-season variability in schistosomiasis infection risk, an association not detected by the regression analysis. Though there are many limitations to this study that temper the potential for causal interpretations, if a high-risk time period could be detected in something close to real time, new prevention options would be opened. Most importantly, we emphasize that traditional regression approaches are usually based on arbitrary pre-specified models, making their parameters difficult to interpret in the context of real-world applications. Our results support the practical application of analysis approaches that, in contrast, do not require arbitrary model pre-specification, estimate parameters that have simple public health interpretations, and apply inference that considers model selection as a source of variation.

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Measuring exposure to Schistosoma japonicum in China. III. Activity diaries, snail and human infection, transmission ecology and options for control

Cited by 26 publications

References 23 publications

Schistosomiasis in the People's Republic of China: the Era of the Three Gorges Dam

Schistosomiasis in the People's Republic of China: the Era of the Three Gorges Dam

Cross-sectional associations between intensity of animal and human infection with Schistosoma japonicum in Western Samar province, Philippines

Using variable importance measures from causal inference to rank risk factors of schistosomiasis infection in a rural setting in China

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