[Study on distribution status of Oncomelania hupensis, the intermediate host of Schistosoma japonicum in Jiangxi Province â ¡ Spatial-temporal distribution of snail-infested environments].

OBJECTIVE: To grasp the status of Oncomelania hupensis snail-infested environments in schistosomiasis endemic areas of Jiangxi Province, and establish the spatial database of snail-infested environments with the administrative village as the unit. METHODS: The spatial and temporal distributions of the historical snail environments, existing snail environments, and suspicious snail-infested environments were analyzed by the historical data review and field investigations. RESULTS: The distribution of snail-infested environments in Jiangxi Province included two popular types of lakeshore and hills. The O. hupensis snail-infested environments were mainly concentrated in the Poyang Lake area, which accounting for 66.97% of the total snail-infested areas. The potential snail-infested environment area was 204 745.48 hm2, among which the potential snail-infested environment areas in the lakeshore and hills were 146 548.58 hm2 and 58 196.90 hm2, accounting for 71.58% and 28.42%, respectively. The real existing snail area was 83 234.50 hm2, among which the real existing snail areas in the lakeshore and hills were 80 890.81 hm2 and 2 343.69 hm2, accounting for 97.18% and 2.82%, respectively. The compressed snail area was 114 253.30 hm2 with a compression rate of 57.85%, of which the compression rates in the lakeshore and hills were 46.51% and 94.97%, respectively. In the four types of snail-infested environments, the areas of Type I, Type II, Type III and Type IV accounted for 55.77%, 25.75%, 13.91% and 4.57% of the total area, respectively. CONCLUSIONS: The spatial database of O. hupensis snail-infested environments is established comprehensively and systematically, that will be conducive to tracking and performing the dynamic updates of the data of snails, so as to provide an important technical support for investigation and monitoring in the future.

[Study on distribution status of Oncomelania hupensis - intermediate host of Schistosoma japonicum in Jiangxi Province I Analysis of distribution of O. hupensis in Poyang Lake area].

OBJECTIVE: To grasp the distribution status of Oncomelania hupensis snails in Poyang Lake area, so as to provide the evidence for formulating and adjusting the schistosomiasis prevention and control strategy in lake areas. METHODS: The vector grid was created and sampled randomly by 200 m × 200 m in the spatial database of grassland, and the distribution of snails was investigated in the selected grid by using the method of mechanical sampling by 50 m × 50 m. At the same time, the elevation of investigation points was extracted based on the topographic map of Poyang Lake. RESULTS: Totally 949 and 210 investigation points were collected from the south and north of Poyang Lake areas, accounting for 3.04% and 3.21% of all the investigation points in the respective region. The number of investigation points, the appearance rate of snail frame, and the average density of alive snails were 15 231, 8.15%, and 0.463/0.1 m2, respectively. The elevation of snail distribution area of the south and north Poyang Lake areas were 11-16 m and 9-16 m respectively. The elevation of concentrated snail belts of the south Poyang Lake area were 12-13 m and 15-16 m, and the elevation of concentrated snail belts of the north Poyang Lake area was 12-14 m. CONCLUSIONS: The distribution of snails is in the range of 9-16 m. The suitable habitats of snail breeding are moving from the south Poyang Lake area to the north Poyang Lake area, and from high elevation to low elevation. In the future, the schistosomiasis prevention and control measures could be formulated based on the geographical characteristics of current snail distribution in order to consolidate the achievements of schistosomiasis control.

[Role of new strategy in transmission control of schistosomiasis in Poyang Lake region].

OBJECTIVE: To evaluate the role of new strategy in the transmission control of schistosomiasis in Poyang Lake region. METHODS: The information and epidemic data of schistosomiasis control were collected and analyzed in Poyang Lake region from 2005 to 2016. RESULTS: After eleven years of carrying out the new strategy, thirteen counties achieved the objective of transmission control in Poyang Lake region. In 2016, the number of schistosomiasis cases and human infection rate were 10 301 and 0.03%, decreased by 89.64% and 99.45% compared with those in 2005, respectively. The number of cattle and schistosome -infected cattle were 68 152 and 5, decreased by 50.84% and 99.83% compared with those in 2005, respectively. The average density of Oncomelania hupensis snails was decreased by 61.52%. No schistosome-infected snails were found since 2014. CONCLUSIONS: The new strategy accurately locates the key points and targets of schistosomiasis transmission chain, which has controlled the human and animal's fecal eggs from polluting grassland, and cut off the transmission chain, reduced both the infection rates of human and animal and the re-infection risk, and promoted to achieve the target of schistosomiasis transmission control in Poyang Lake region.

[Study on cut-off value of IHA method for schistosomiasis diagnosis in different endemic areas].

OBJECTIVE: To explore the cut-off value of the indirect haemagglutination test (IHA) method for schistosomiasis japonica diagnosis in different endemic areas. METHODS: Totally 55 nature villages of the lake-type endemic counties, Yugan and Xinzi, in Poyang Lake Region of Jiangxi Province were chosen as the study fields, and all the villagers over 5 years old were parallelly examined by Kato-Katz method + miracidial hatching test and IHA method. The detection data were analyzed by the correlation analysis, and the threshold values of the IHA method in different endemic areas were decided by the receiver operating characteristic (ROC) curve. RESULTS: The positive rate of stool examinations of the villagers was correlated with the distribution trend of the antibody level of whole population (r = 0.588, P ＜ 0.05), but no correlation with the antibody level of the positive population (r = 0.221, P ＞ 0.05). The antibody level of stool-negative population during the period of 2008 to 2011 detected by IHA method dropped year by year, and the annual difference was statistically significant (F = 3.650, P ＜ 0.05). While the antibody level of stool-positive population found during the period of 2008 to 2011 maintained a certain high level in the 4 years, and there was no statistically significant difference among them (F = 2.461, P ＞ 0.05). When the positive rates were <1%, 1%-5% or >5%, the specificity of diagnosis could be improved when 1∶80, 1∶20 and 1∶10 were used as the cut-off values of IHA correspondingly. CONCLUSIONS: The different threshold values for diagnosis of schistosomiasis japonica should be considered while using IHA method to screen out patients in different endemic areas.