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Objective: To explore the spatial pattern of the distribution of Oncomelania hupensis population in marshland and lake region., Methods: Four bottomlands were selected randomly for the investigation along the Qiupu River in Guichi District, Anhui Province. The quadrats were placed randomly for snail survey, and the mean crowding, mean density, aggregation indices (diffusion coefficient (C), morisita index (Idelta), index of patchiness (m*/m) ), Taylor's power law and Iwao's m*-m regression index were analyzed., Results: For 4 bottomlands in different time, the diffusion coefficients, Morisita indices, and m*/m indices were all more than one. There was a close linear relationship between the logarithm of the snail density and its variance (P < 0.01), and the correlation coefficient was 0.972. In Taylor's power law, the lg a was 0.602 and b was 1.427. There was a close linear relationship between the mean crowding (m*) and the snail density (m) (P < 0.01), and the correlation coefficient, alpha and beta was 0.984, 2.367 and 1.617 respectively., Conclusion: The spatial pattern of Oncomelania hupensis population shows an aggregation distribution in marshland and lake region, and the basic components of snail distribution are in colonies.

Objective: To explore the degree of genetic diversity among populations of Oncomelania hupensis., Methods: AFLP method was used to amplify the genomic DNA of thirteen snail populations from nine provinces (i. e. Yunnan, Sichuan, Guangxi, Fujian, Hunan, Hubei, Jiangxi, Anhui and Jiangsu) and the genetic diversities among snail populations were analyzed., Results: The number of AFLP fragments amplified ranged from 403 to 472 for thirteen Oncomelania populations. Among the thirteen snail populations, the genetic diversity within the population from Xingzi County, Jiangxi Province, was most significant, and the percentage of polymorphic loci, Nei's genetic diversity and Shannon's information index were 93.22%, 0.345 and 0.510 respectively, while these indices for the snail population from Yizhou City, Guangxi Region, were the lowest, 55.80%, 0.191 and 0.287 respectively. The similarity between the in-group-individuals from Yizhou City, Guangxi Region, was most significant, and the average coefficient of similarity was 0. 904, and that from Dantu County, Jiangsu Province, was the lowest (0.748). The genetic diversities among snail populations were significantly different for the thirteen snail populations (P < 0.01)., Conclusion: There is a certain genetic variation among Oncomelania snail populations from the mainland of China, and this variation is significantly different among snail populations from different areas.

Objective: To specify the trends of endemic situation among twenty one national surveillance sites for schistosomiasis from 2000 to 2004., Methods: According to the national surveillance protocol, longitudinal surveillance on endemic situation of schistosomiasis was carried out at twenty-one sites since 2000., Results: The infection rate of Schistosoma japonicum declined in six of the twenty-one surveillance sites. The density of living snails and of infected snails decreased in two sites but not well controlled in most other sites. The prevalence in cattle fluctuated yearly in most sites and maintained at a relatively high level. During the surveillance period, acute cases were found annually and the number of advanced patients did not increase significantly. No new case and infected snails were found in Jinshan, Shanghai, since 2000, where transmission of schistosomiasis was interrupted two decades ago., Conclusion: Routine control strategies such as selective chemotherapy combined with livestock chemotherapy, snail control in risk areas have a positive impact on the control of schistosomiasis. However, these strategies should be lasted for longer time and the surveillance on snails and cattle should be continued.

Objective: To search into a method for analyzing the quantitative data in amplified fragment length polymorphism (AFLP) electrophoresis., Methods: Oncomelania snails collected from the field were screened. Forty snails found uninfected with schistosomiasis were divided randomly into two groups and used to isolate genomic DNA. AFLP electrophoresis pattern was first transformed into quantitative data by Glyko BandScan software, and the bands were read according to different standards of band-reading to acquire the corresponding data. These data sets were analyzed by genetic statistics to get an inference set, and the analysis of this inference set was performed to reach a summary description., Results: The results of genetic variation from different standards of band-reading were different With the increase of the standard value of band-reading, the indices indicating the genetic polymorphism of Oncomelania hupensis population (e.g. Shannon's information index) also increased. When the standard value reached at certain level, the values of these indices began to decrease. Compared with the above indices, the change for gene flow turned out contrary to the genetic identity. The distributions of inference results from different standards of band-reading all showed significant normal distribution. The mean value of genetic variation based on total grey was very close to that on the proportion of total grey. The average genetic identity between the "subpopulations" was 0.956 according to proportion of total grey or 0.958 from the total grey with an average genetic distance between the "subpopulations" of 0.045 and 0.043 respectively., Conclusion: It seems to be a reasonable and accurate method by quantifying the AFLP electrophoresis pattern followed by analyzing the data through the use of the different standards of band-reading.

Objective: To explore the correlation of the ultrasound indices of liver and spleen in schistosomiasis japonica and with infection frequency, infection time and EPG., Methods: The canonical correlation was applied to analyze the correlation of the hepatosplenic ultrasound indices in schistosomiasis japonica, and the correlation of the ultrasound indices with infection frequency, infection time and EPG. The proportions of variation related to each other in liver and spleen were analyzed by the redundancy analysis., Results: The correlation coefficients of the first pair correlation canonical variable were 0.7842, 0.5483 and 0.5800, 0.4220, respectively, in males and females without infection, males and females with infection history (P<0.01). The correlation coefficients of the first pair correlation canonical variable were 0.6063, 0.5215 and 0.6595, 0.3849, respectively, in male negatives and female negatives, male positives and female positives (P<0.01). In groups of males and females without infection, the variations of liver ultrasound indices related with the variation of spleen ultrasound indices were 43.5% and 17.5% respectively, and in groups infection history, they were 22.1% and 11.4% respectively. In male and female negative groups, the variations of liver ultrasound indices related with the variation of spleen ultrasound indices were 26.8% and 16.8% respectively, and in positive groups, they were 27.6% and 10.7% respectively. The infection frequency, infection time and EPG in the stool-positive groups were not significantly related with the canonical variables of liver and spleen ultrasound indices (P>0.05)., Conclusion: There is a significant canonical correlation between the liver and spleen ultrasound indices in schistosomiasis japonica, especially in males. In groups with infection history, the infection frequency, infection time and EPG of those stool-positives are not relevant to the canonical variables of liver and spleen ultrasound indices.

Objective: To identify the trends of endemic situation at the twenty-one national surveillance sites from 2000 to 2002., Methods: According to the protocol of the national surveillance system, longitudinal surveillance of endemic situation of schistosomiasis was carried out at the twenty-one surveillance sites since 2000., Results: Relative indexes of endemic situation of schistosomiasis decreased in two surveillance sites annually. The infection rate of Schistosoma japonicum in human population decreased in most surveillance sites. The infection rate of cattle decreased in eight surveillance sites. However, acute cases were found in two sites each year. The density of live snails and infected snails was higher compared with that in 2000 among eight sites and infected snails were found in inner embankment in Junshan surveillance sites. Hunan Province, in 2002 at first time. The snail ridden areas increased significantly in Fengjin sites, Shanghai, where schistosomiasis was eliminated years ago., Conclusion: Current control strategies have some impact on the morbidity of schistosomiasis. However, these strategies should be lasted for longer time and surveillance on snails should be enhanced.