[Analysis of Oncomelania hupensis status in schistosomiasis surveillance sites of Yunnan Province in 2015].

OBJECTIVE: To understand the Oncomelania hupensis distribution and infection status in the schistosomiasis surveillance sites of Yunnan Province, so as to provide the evidence for making the control and prevention measures. METHODS: Eighteen administrative villages were selected as the surveillance sites where the schistosomiasis endemic was serious in 18 epidemic counties, one village for one county. The snail status was investigated with the systematic sampling and environmental sampling methods, and the infection status of the snails was detected by a microscope and loop-mediated isothermal amplification (LAMP). The surveillance database was established and descriptively analyzed. RESULTS: In 2015, the total surveillance area was 1826.55 hm², and the area with snails was 55.03 hm², that was reduced by 57.70% as compared to that in 2013, and by 40.63% as compared to that in 2014. No new snail area was discovered, and also no schistosome infected snails were discovered. Totally 718,532 frames were surveyed, and the occurrence rate of frames with snails was 0.45% and the density of living snails was 0.013 9 snail/0.1 m². In the endemic controlled areas, the snail area and density of living snails were both the highest. The snails concentrated on the environments of paddy field, ditch, bottomland, small reservoir, and dry land, and the vegetations of rice, dry crop, weed and wood. The snail area, occurrence rate of frames with snails, total number of snails and number of living snails all showed a downward trend. No infected snails were found for three years. CONCLUSIONS: The Oncomelania hupensis snails have been effectively controlled in the national schistosomiasis surveillance sites of Yunnan Province. However, the comprehensive snail control measures still should be continually strengthened in order to consolidate the achivements.

[Runoff Pollution Experiments of Paddy Fields Under Different Irrigation Patterns].

To study runoff and non-point source pollution of paddy fields and to provide a scientific basis for agricultural water management of paddy fields, paddy plots in the Jintan City and the Liyang City were chosen for experiments on non-point source pollution, and flood irrigation and intermittent irrigation patterns were adopted in this research. The surface water level and rainfall were observed during the growing season of paddies, and the runoff amount from paddy plots and loads of total nitrogen (TN) and total phosphorus (TP) were calculated by different methods. The results showed that only five rain events of totally 27 rainfalls and one artificially drainage formed non-point source pollution from flood irrigated paddy plot, which resulted in a TN export coefficient of 49.4 kg · hm⁻² and a TP export coefficient of 1.0 kg · hm⁻². No any runoff event occurred from the paddy plot with intermittent irrigation even in the case of maximum rainfall of 95.1 mm. Runoff from paddy fields was affected by water demands of paddies and irrigation or drainage management, which was directly correlated to surface water level, rainfall amount and the lowest ridge height of outlets. Compared with the flood irrigation, intermittent irrigation could significantly reduce non-point source pollution caused by rainfall or artificial drainage.

[Molluscicidal effect of 5% powder of niclosamide ethanolamine salt granules (NEG) in field of mountainous areas in Yunnan Province].

OBJECTIVE: To evaluate the molluscicidal effect of 5% powder of niclosamide ethanolamine salt granules (NEG) in the field of mountainous areas in Yunnan Province. METHODS: The grasslands with Oncomelania hupensis snail habitats were chosen in Beideng Village, Heqing County, Yunnan Province, and were divided into 7 groups (groups of NEG 30 g/m2, NEG 40 g/m2, NEG 50 g/m2, NEG 40 g/m2 plus obstacle clearing, 50% niclosamide ethanolamine salt wettable powder (WPN) 6 g/m2, WPN 6 g/m2 plus obstacle clearing, and fresh water). The snail death rates and the densities of living snails were investigated and the results were compared in the different groups 7 d, 15 d, and 30 d after the implementation. RESULTS: Seven d, 15 d, and 30 d after the implementation, the snail death rates of the groups of NEG 30 g/m2, 40 g/m2, and 50 g/m2 were from 72.75 % to 95.83%, and the average descent rates of living snail densities were from 72.26% to 95.54%. Seven d, 15 d, and 30 d after the implementation, in the NEG 40 g/m2 group, the snail death rates were from 81.69% to 87.19%, and the average descent rates of living snail densities were from 81.42% to 87.91% ; in the NEG 40 g/m2 plus obstacle clearing group, the snail death rates were from 84.89% to 88.24% and the average descent rates of living snail densities were from 85.63% ~ 88.22%; in the WPN 6 g/m2 group, the snail death rates were from 85.23% to 86.17% and the average descent rates of living snail densities were from 85.76% to 86.05%; in the WPN 6 g/m2 plus obstacle clearing group, the snail death rates were from 88.89% to 92.10% and the average descent rates of living snail densities were from 86.71% to 92.20%. The obstacle clearing improved the molluscicidal effect. CONCLUSION: NEG has a good molluscicidal effect in the field of mountainous areas in Yunnan Province.

[Analysis of schistosomiasis endemic status of national surveillance sites in Yunnan Province, 2014].

OBJECTIVE: To master the dynamic endemic status and influencing factors of schistosomiasis in Yunnan Province, so as to provide the evidence for making the control and prevention measures. METHODS: Four villages of four schistosomiasis heavy endemic counties were selected as survey sites. Then, the serological screening and etiological tests were carried out in the residents, and the basic situations of the survey sites were investigated. The infection status of the livestock and relevant information of Oncomelania hupensis snails were surveyed. All the results were analyzed statistically. RESULTS: Totally 4310 residents were surveyed by the indirect hemagglutination assay with the examination rate of 79.68% and serum positive rate of 8.40%. The positive rate reached upwards 12.53% in Qiandian Village of Eryuan County. The serum positive rate of the female was higher than that of the male, and the positive rates of the 30 years and older age groups were higher than those of the other age groups. The serum positive rates of the peasants, migrant labourers and residents with the junior high school education level were higher. No positive feces were found. A total of 24 advanced cases were reported. No positive livestock and snails were found, and the average density of living snails was 0.023 3-0.056 6/0.1 m2. CONCLUSION: Right now, the schistosomiasis is at a low prevalence status in Yunnan Province, and the endemic situation has been effectively controlled.

[Study on spatio-temporal pattern of mountainous Oncomelania hupensis snails at village scale in Eryuan County, Yunnan Province].

OBJECTIVE: To develop a spatio-temporal model of mountainous Oncomelania hupensis snails based on the Bayesian model, and to analyze and identify the spatio-temporal pattern at a village scale. METHODS: The data including the intensity and spatial distribution of live and infected snails from 2000 to 2006 and the village boundary were collected. The independent and interactive spatio-temporal models were established, and then the best fitness model was selected to analyze the spatio-temporal pattern of live and infected snails. RESULTS: The interactive model of live snails and the independent model of infected snails were relative fitness models, and the models showed 95% CI (confidence interval) of the spatial and temporal coefficient included zero, and indicated that the spatial and temporal correlation of live and infected snails was not significant at a village scale. CONCLUSION: There is no significant spatial and temporal correlation of live and infected mountainous snails at a village scale, and the furthermore study should be carried out at a small scale.

[Effect of a novel plant molluscicide "Luo-wei" against Oncomelania hupensis in plateau mountain areas].

OBJECTIVE: To evaluate the effect of a novel plant molluscicide, 4%"Luo-wei" (Tea-seed distilled saponins, TDS) against Oncomelania hupensis snails in plateau mountain areas in Yunnan Province. METHODS: The immersing and spraying experiments were carried out in the ditches and grassland of Xiaolian Administrative Village in Heqing County, Yunnan Province, to assess the molluscicidal effect of 4% TDS comparing with 50% wettable powder of niclosamide ethanolamine salt (WPN) in different environments and time. RESULTS: After immersion for 24, 48 h and 72 h, the snail death rates were 70.67%, 87.33% and 98.67% in the TDS group, whereas being 77.33%, 96.67% and 100.00% in the WPN group, respectively. The differences of the death rates between the two groups 24 h and 72 h after immersing were not statistically significant ( chi2(24h) =1.73, chi2(72h) = 2.01, both P values > 0.05). Seven days after the immersing experiments, the occurrence rate of frames with living snails and the death rate of snails were 20.00% and 93.03% in the TDS group, while those were 13.33% and 95.76% in the WPN group, and there were no significant differences of the 2 indexes between the 2 groups ( chi(2)(Occurrence rate) = 2.27, chi(2)(Death rate) = 0.94, all P values > 0.05). After spraying for 1, 3, 7 d and 15 d, in both groups, the occurrence rates of frames with living snails and the average densities of living snails gradually declined, while the death rates of snails gradually increased with the extension of time. There were no statistically significant differences of the above 3 indexes between the 2 groups (all P values > 0.05). Fifteen days after the spraying experiment, the occurrence rate of frames with living snails and the adjusted death rate of snails were 15.00% and 87.39% in the TDS group and those were 16.67% and 89.32% in the WPN group, respectively. CONCLUSION: The molluscicidal effect of TDS is satisfying in plateau mountain areas, and the molluscicide is worthy of further extension and application.