A new surveillance and response tool: Risk map of infected Oncomelania hupensis detected by Loop-mediated isothermal amplification (LAMP) from pooled samples

Although schistosomiasis remains a serious health problem worldwide, significant achievements in schistosomiasis control has been made in the People's Republic of China. The disease has been eliminated in five out of 12 endemic provinces, and the prevalence in remaining endemic areas is very low and is heading toward elimination. A rapid and sensitive method for monitoring the distribution of infected Oncomelania hupensis is urgently required. We applied a loop-mediated isothermal amplification (LAMP) assay targeting 28S rDNA for the rapid and effective detection of Schistosoma japonicum DNA in infected and prepatent infected O. hupensis snails. The detection limit of the LAMP method was 100 fg of S. japonicum genomic DNA. To promote the application of the approach in the field, the LAMP assay was used to detect infection in pooled samples of field-collected snails. In the pooled sample detection, snails were collected from 28 endemic areas, and 50 snails from each area were pooled based on the maximum pool size estimation, crushed together and DNA was extracted from each pooled sample as template for the LAMP assay. Based on the formula for detection from pooled samples, the proportion of positive pooled samples and the positive proportion of O. hupensis detected by LAMP of Xima village reached 66.67% and 1.33%, while those of Heini, Hongjia, Yangjiang and Huangshan villages were 33.33% and 0.67%, and those of Tuanzhou and Suliao villages were 16.67% and 0.33%, respectively. The remaining 21 monitoring field sites gave negative results. A risk map for the transmission of schistosomiasis was constructed using ArcMap, based on the positive proportion of O. hupensis infected with S. japonicum, as detected by the LAMP assay, which will form a guide for surveillance and response strategies in high risk areas.     

Infestation risk of the intermediate snail host of Schistosoma japonicum in the Yangtze River Basin: improved results by spatial reassessment and a random forest approach

Background::Oncomelania hupensis is only intermediate snail host of Schistosoma japonicum, and distribution of O. hupensis is an important indicat...     

Schistosomiasis control in the 21st century. Proceedings of the International Symposium on Schistosomiasis,Shanghai, July 4-6, 2001

A total of 120 papers were presented at the International Symposium on Schistosomiasis which was held in Shanghai, July 4-6, 2001 with the theme of Schistosomiasis Control in the 21st Century. In order to focus more attention on the new challenges in control programmes for schistosomiasis as well as show the priority of research areas in new century, we summarize the advances of control programmes and researches in nine areas, including (1) Status of schistosomiasis control programmes; (2) Progress in applied field research; (3) Biology and control approaches of snail hosts; (4) Novel approaches for schistosomiasis control; (5) Pathogenesis and morbidity of the disease; (6) Immunology and vaccine development; (7) Screening of population for chemotherapy in low transmission areas; (8) Sustainable intervention methods in different endemic settings; (9) Impact of animal schistosomiasis on agricultural development and importance of its control; (10) GIS/RS application and environmental changes.     

Rapid screening method for Schistosoma japonicum infection using questionnaires in flood area of the People's Republic of China

A rapid, simple, and effective method using questionnaires is described for screening of high-risk individuals of schistosomiasis japonica after the occurrence of major flooding. A case-control study design was adopted in two randomly selected villages from Dongting Lake area in the People's Republic of China that are endemic for Schistosoma japonicum. Information about contagious water exposure history and several other risk factors were collected retrospectively from 246 individuals, aged 9-60 years. A probability model was developed by logistic regression analysis, which included six variables, namely (i) knowledge of Schistosoma transmission, (ii) education attainment, (iii) annual income before flood year per person, (iv) duration of contagious water exposure due to swimming and paddling, (v) intensity of contagious water exposure due to occupational activities, and (vi) duration of contagious water exposure due to recreational activities. The receiver-operating characteristic (ROC) curve was plotted and the sensitivity and specificity were calculated. The internal consistency of the probability model was good. The area below the ROC curve was 0.90. If the probability cutoff value of diagnosing an infection with S. japonicum was defined as 0.35, both sensitivity and specificity were above 82%, whereas positive and negative predictive values were 70 and 91%, respectively. We conclude that questionnaires are a viable tool for screening of high-risk individuals of S. japonicum infections in lake communities of China after flooding occurred, opening new avenues for schistosomiasis control.     

Immune correlate study on human Schistosoma japonicum in a well-defined population in Leyte,Philippines: I. Assessment of 'resistance' versus 'susceptibility' to S. japonicum infection

This study describes the categorical classification of 155 individuals living in an endemic village in Macanip, Leyte, Philippines as 'resistant' or 'susceptible' to Schistosoma japonicum infection using available exposure, infection and reinfection data collected from a 3-year water contact (WC) study. Epidemiological parameters including age, sex, and infection intensities in relation to observed reinfection patterns are also described. This classification was used in subsequent immunological studies described in two accompanying papers to identify protective immune mechanisms among resistant individuals induced by defined candidate vaccine molecules for S. japonicum. The study suggests that individuals who were most vulnerable to rapid reinfection were children belonging to the 5-14 age group. A drop in incidence at age group 15-19 and decreased intensity of infection starting at this age group and older (15+) suggests development of immunity. Controlling for the effect of the other variables, a multivariate analysis showed significant association for sex, in that females were more likely to be resistant. This implies that other than acquired immunity to infection, some age-dependent host factors may also play an important role in the overall changes of reinfection patterns seen in schistosomiasis japonica in this population.