An integrated environmental improvement of marshlands: impact on control and elimination of schistosomiasis in marshland regions along the Yangtze River, China.

BACKGROUND: Schistosomiasis is a global snail-transmitted infectious disease of poverty. Transmission control had been achieved in China in 2015 after the control efforts for over 60 years. Currently, the remaining core regions endemic for Schistosoma japonicum are mainly located in the marshland and lake regions along the Yangtze River basin. METHODS: During the period from 2001 through 2015, an integrated environmental improvement of the marshlands was carried out through the implementation of industrial, agricultural and resources development projects in Yizheng County along the Yangtze River. S. japonicum infection in humans, livestock and snails was estimated by serology, stool examination, hatching technique and microscopy during the 15-year study period to evaluate the effect of the integrated environmental improvement on control and elimination of schistosomiasis. RESULTS: A 0.05% overall rate of S. japonicum infection was observed in snails during the 15-year study period, and no infected snails were detected since 2012. The overall prevalence of S. japonicum infection was 0.09% in humans during the study period, and no human infection was found since 2012. In addition, only 13 bovines were identified with S. japonicum infection in 2003 during the 15-year study period, and since 2004, no infection was found in livestock. CONCLUSION: The results of the present study demonstrate that the implementation of industrial, agricultural and water resources development projects, not only alters snail habitats in marshland regions, and promotes local economic development, which appears a win-to-win strategy to block the transmission of S. japonicum and accelerate socio-economic development along the Yangtze River.

[Improvement of root parameters in land surface model (LSM )and its effect on the simulated results].

In order to improve root parameterization in land surface model, the sub-model for root in CERES-Maize was coupled in the SSiB2 after calibrating of maize parameters in SSiB2. The effects of two improved root parameterization schemes on simulated results of land surface flux were analyzed. Results indicated that simulation accuracy of land surface flux was enhanced when the root module provided root depth only with the SSiB2 model (scheme I). Correlation coefficients between observed and simulated values of latent flux and sensible flux increased during the whole growing season, and RMSE of linear fitting decreased. Simulation accuracy of CO2 flux was also enhanced from 121 days after sowing to mature period. On the other hand, simulation accuracy of the flux was enhanced when the root module provided root depth and root length density simultaneously for the SSiB2 model (scheme II). Compared with the scheme I, the scheme II was more comprehensive, while its simulation accuracy of land surface flux decreased. The improved root parameterization in the SSiB2 model was better than the original one, which made simulated accuracy of land-atmospheric flux improved. The scheme II overestimated root relative growth in the surface layer soil, so its simulated accuracy was lower than that of the scheme I.

[Integration and demonstration of key techniques in the surveillance and forecast of schistosomiasis in Jiangsu Province II Molluscicidal effect of 5% niclosamide ethanolamine granules in large-scale settings].

OBJECTIVE: To evaluate the field molluscicidal effect of 5% niclosamide ethanolamine granules, so as to provide a novel Oncomelania hupensis snail control approach for emergency treatment of high-risk settings. METHODS: Snail control tests with spraying of 5% niclosamide ethanolamine granules were conducted in two settings of 2 counties, and the dose-, time- and setting-specific field molluscicidal effects were tested. RESULTS: In the small-scale setting, spraying of 5% niclosamide ethanolamine granules at doses of 30, 40 and 50 g/m2 resulted in 54.55%, 68.41% and 73.45% 1-day snail mortality, 57.27%, 68.59% and 80.28% 3-day snail mortality, and 63.49%, 77.58% and 85.55% 7-day snail mortality, respectively, and no significant differences were detected in 1- and 3-day snail mortality caused by spraying of 5% niclosamide ethanolamine granules at doses of 30 and 40 g/m2 (all P > 0.05), while significant difference was found in the 7-day snail mortality (χ2 = 4.549, P < 0.05). In addition, spraying of 5% niclosamide ethanolamine granules at doses of 40 and 50 g/m2 resulted in comparable 1-, 3- and 7-day snail mortality (all P > 0.05). In the large-scale setting, spraying of 5% niclosamide ethanolamine granules at a dose of 40 g/m2 resulted in 85.29% and 87.70% 3-day snail mortality, 83.89% and 91.02% 7-day snail mortality, and 83.41% and 91.84% 15-day snail mortality in the environment-cleaning group and non-cleaning group, respectively. The overall snail mortality was 90.02% in the environment-cleaning group 3 to 15 days after spraying, which was significantly higher than that (84.28%) in the non-cleaning group (χ2 = 9.950, P < 0.05). After 15 days of spraying with 5% niclosamide ethanolamine granules at a dose of 40 g/m2, the densities of living snails reduced from 19.90 and 19.83 snails/0.1 m2 to 0.60 and 2.60 snails/0.1 m2 in the environment-cleaning group and non-cleaning group, with 96.98% and 86.89% reductions, respectively. CONCLUSION: The appropriate dose of 5% niclosamide ethanolamine granules is 40 g/m2 for snail control in the field, and environment cleaning of vegetation with a height of more than 50 cm may improve the molluscicidal efficacy.

[Correlation between schistosomiasis endemic situation and Oncomelania snail status in Yizheng City, Jiangsu province from 2002 to 2011].

OBJECTIVE: To understand the correlation between schistosomiasis endemic situation and Oncomelania snail status, and discuss the control strategy and measures. METHODS: With a retrospective research method, the data were collected and analyzed including the snail area, infected snail area, snail density, density of infected snails, the infection rate of snails, the positive rates of blood tests and stool examinations for schistosomiasis in residents and domestic animals, and the incidence of acute schistosome infection in Yizheng City from 2002 to 2011. The correlation between the infected snails and schistosomiasis was analyzed. RESULTS: There were decline trends in snail area, infected snail area, and schistosomiasis situation. There were positive correlations between the infected snail area and snail area (r = 0.732, P < 0.05), the occurrence of acute schistosomiasis patients and infected snail area (r = 0.678, P < 0.05), and the snail area and schistosome infection rate of residents (r = 0.774, P < 0.05). CONCLUSION: In order to control schistosomiasis, we need to control infected snails, reduce snail areas, and implement comprehensive control measures.

[Effect of water conservancy schistosomiasis control projects in rivers and estuaries connecting with the Yangtze River on Oncomelania snail control].

OBJECTIVE: To evaluate the effect of the water conservancy schistosomiasis control projects in rivers and estuaries connecting with the Yangtze River on Oncomelania snail control. METHODS: Three water conservancy schistosomiasis control projects of Laobianmin River, Panjia River and Bianmin River were chosen for the objects of the study. The concrete slope protection and the overflow dam, the concrete slope protection and the check sluice, and the simple concrete slope protection were built respectively in above mentioned three rivers. The changes of the area with snails and density of snails were investigated before and after the interventions, and the results were compared among the three projects. RESULTS: In the condition of the routine snail control with the molluscicide, the snails were eliminated in the main riverway of the Laobianmin River, but the snails still existed in the target protected area (tributaries of the river and irrigation areas); the snails were eliminated in the Panjia River and its irrigation areas; in the Bianmin River, the areas with snails dropped by 89.22% in the main river and still remained in the tributaries and irrigation areas after the project implementation. CONCLUSIONS: The sluice and overflow dam more contribute to control and eliminate snails in the project areas and the target protected areas in the rivers and estuaries connecting with the Yangtze River. The priority of consideration should be given to the water level control and prevention of snail spreading in the water level instability rivers connecting with the Yangtze River.