[Effect of integrated schistosomiasis control measures in Hunan Province from 2004 to 2019].

OBJECTIVE: To examine the effect of the integrated schistosomiasis control measures in Hunan Province from 2004 to 2019, so as to provide insights into the development of the schistosomiasis elimination strategy. METHODS: The integrated schistosomiasis control measures implemented by the health, agriculture, water resources, forestry, land and resources sectors were retrospectively collected in Hunan Province from 2004 to 2019, and the completion of each measure, cost of control measures, Schistosoma japonicum infections in humans and bovines, and snail status were analyzed each year. An index system for assessing the integrated schistosomiasis control effect was constructed using the Delphi method to calculate the integrated schistosomiasis control effect index. In addition, a cost-effect analysis was performed in terms of the decline in the prevalence of S. japonicum infections in humans and bovines, areas with snails in inner embankments, and areas with infected snails. RESULTS: A total of 7 110 926 500 Yuan were invested into the integrated schistosomiasis control program of Hunan Province from 2004 to 2019. During the 16-year period, a total of 277 437.12 hm2 snail habitats received molluscicidal treatments, 6 927 230 person-times given expanded chemotherapy, 2 116 247 bovine-times given expanded chemotherapy, 954 850 harmless toilets built, 290 359 bovines fenced, 136 666 bovines eliminated, 141 905 machines used to replace bovines, 39 048.63 hm2 water lands improved as dry lands, 724.12 km irrigation regions improved, 3 994 300 populations covered with safe water, 191 102.89 hm2 forests planted and 38 535.27 hm2 lands leveled. The prevalence of S. japonicum infections was 4.29% in humans and 4.48% in bovines in Hunan Province in 2004, with 2 449.37 hm2 snail habitats in inner embankments and 3 423.74 hm2 infected snail areas. In 2019, the prevalence of S. japonicum infections reduced to 0 in both humans and bovines, and areas of snail habitats reduced to 540.92 hm2 (77.92% reductions), while the areas with infected snails reduced to 0. The overall integrated schistosomiasis control effect index appeared a tendency towards a rise over years since 2004, and the integrated schistosomiasis control effect index was 97.35 in 2019; the annual mean costs for a 1% reduction in the prevalence of S. japonicum infections in 100 populations and 100 bovines were 70.11 Yuan and 4 204.78 Yuan, and the annual mean costs for a 1% reduction in the snail areas in inner embankments and infected snail areas were 2 010.20 Yuan and 1 298.09 Yuan, respectively. CONCLUSIONS: The integrated control measures achieve remarkable effectiveness for schistosomiasis control in Hunan Province, with a remarkable decline in the prevalence of S. japonicum infections in humans and bovines and great shrinking of snail areas in inner embankments and infected snail areas. Adequate fund investment is required to improve the integrated schistosomiasis control measures and consolidate the control achievements.

[Comparison of molluscicidal cost and effectiveness between 5% niclosamide ethanolamine salt granules and 26% suspension concentrate of metalaldehyde and niclosamide ethanolamine salt].

OBJECTIVE: To compare the molluscicidal effects and cost-effectiveness of 5% niclosamide ethanolamine salt granules (NEG) and 26% suspension concentrate of metalaldehyde and niclosamide ethanolamine salt (MNSC) . METHODS: Two plots with high Oncomelania hupensis snail density were selected as research areas in Nanjing Chemical Industry Zone, and 5% NEG (40 g/m2) and 26% MNSC (40 g/m2) were used by the spraying method for snail control in the two plots, and their molluscicidal effects and cost-effectiveness were investigated and statistically analyzed. RESULTS: There was no significant difference between 5% NEG and 26% MNSC in the molluscicidal effects. The cost of 5% NEG was 1.25 times higher than that of 26% MN-SC per ten thousand square meters in snail control. CONCLUSIONS: The cost of 5% NEG is higher than that of 26% MNSC per ten thousand square meters in snail control. Their molluscicidal effects are similar.

[Effect and cost-effectiveness of three commonly used molluscicides in largescale field application].

OBJECTIVE: To evaluate the effect and cost-effectiveness of three commonly used molluscicides, 4% "Luo-wei" (tea-seed distilled saponins, TDS), 50% niclosamide ethanolamine salt wettable powder (NESWP), and 26% metaldehyde and niclosamide suspension concentrate (MNSC) in large-scale field application, so as to provide the references for formulating the strategy of snail control. METHODS: The field test and parallel comparison were implemented. A marshland with Oncomelania hupensis snails of the Yangtze River was divided into 4 parts (10 hm2) for the research, and three of them were experimental areas while the last one was a blank control area. The experimental areas were sprayed with 4% "Luo-wei", 50% NESWP and 26% MNSC respectively for 3 times and the interval was 1 week. Seven days after each spraying the effect of snail control was investigated, and the costs of molluscicides, labor, transportation, fuel consumption and mechanical loss were recorded. The cost of each molluscicide, snail mortality, snail density, and the cost of increasing 1% of snail mortality per 100 m2 were analyzed and compared. RESULTS: After the first, second and third spraying, the corrected snail mortality rates were 67.34%, 76.55% and 84.60% respectively in the 4% "Luo-wei" group; the corrected snail mortality rates were 64.71%, 75.17% and 83.89% respectively in the 50% NESWP group; the corrected snail mortality rates were 66.55%, 76.27% and 86.67% respectively in the 26% MNSC group. There was no significant difference among the 3 groups in the snail mortality at the same spraying time (χ2 = 1.590, 0.571, 3.238, all P > 0.05) . In addition, along with the increase of the spraying times, the snail mortality of each group was increased significantly compared to that of the control group (χ2 = 79.333, 94.718, 117.020, all P < 0.01) . After the first, second and third spraying, the reduction rates of snail density were 69.82%-86.60% in the 4% "Luo-wei" group, 68.66%-86.55% in the 50% NESWP group, and 71.89%-88.87% in the 26% MNSC group respectively. The decreasing amplitude of the snail density was more than 85% in all the experimental areas after 3 rounds of spraying molluscicide. The snail control costs per 100 hm2 were 19.57, 11.97 Yuan and 10.47 Yuan in the 4% "Luo-wei" group, 50% NESWP group, and 26% MNSC group respectively. After the first, second and third spraying, the costs of increasing 1% of snail mortality per 100 m2 were 0.30, 2.08 Yuan and 2.38 Yuan in the 4% "Luo-wei" group, 0.20, 1.10 Yuan and 1.32 Yuan in the 50% NESWP group, and 0.17, 1.04 Yuan and 0.97 Yuan in the 26% MNSC group respectively, and the cost-effectiveness was the highest at the first spraying in all the three groups. CONCLUSIONS: The effects of the three molluscicides for snail control are similar, but the efficacy of snail control is reduced as the spraying time increases.

[Effects and cost of four formulations of niclosamide ethanolamine salt in Oncomelania hupensis snail control in field].

OBJECTIVE: To investigate the effects and cost of four formulations of niclosamide ethanolamine salt in Oncomelania hupensis snail control in the field in marshland and lake regions, so as to provide the evidence for drawing up the plan of molluscicide using in schistosomiasis endemic areas. METHODS: One drainage channel and one channel without water in the same area with snails in Jiangling County, Jingzhou City were selected as the research fields. The drainage channel was divided into 9 sections, except one section as a blank control group where the natural death rate of snails was observed only, and the remaining 8 sections were taken as the observation groups, where different dosages of 4% niclosamide ethanolamine salt powder, 5% niclosamide ethanolamine salt granules, 25% niclosamide ethanolamine salt suspending agent, 26% metaldehyde and niclosamide ethanolamine salt suspending agent, and 50% niclosamide ethanolamine salt wettable powder were used respectively. The channel without water were divided into 4 sections, except one section as a blank control group, the other 3 segments were taken as the observation groups, where 4% niclosamide ethanolamine salt powder, 5% niclosamide ethanolamine salt granules, and 50% niclosamide ethanolamine salt wettable powder were used respectively. Before and after spraying molluscicide for 7 days and 15 days, the system sampling method was used to observe the effects of snail control. Meanwhile, the unit cost method was used to calculate the costs of the different mulluscicide formulations abovementioned in unit area (1 m2). RESULTS: In the field at the drainage channel, the snail mortality rates of the groups spraying 4% niclosamide ethanolamine salt powder (50 g/m2), 5% niclosamide ethanolamine salt granules (40 g/m2), 25% niclosamide ethanolamine suspending agent, 26% metaldehyde and niclosamide ethanolamine salt suspending agent, and 50% niclosamide ethanolamine salt wettable powder (2 g/m2 and 4 g/m2) for 7 days were 79.52%97.87%, while the rates after spraying for 15 days were 71.00%-96.30%, and compared with those before spraying, the differences were statistically significant (all P < 0.01). For the groups spraying with 2 g/m2 or 4 g/m2 suspending agent as well as wettable powder for 7 days, the snail mortality rates were significantly different (both P < 0.05). In the field at the channel without water, the snail mortality rates of the 3 observation groups after spraying molluscicide for 7 days were 97.14%-100%, while for 15 days were 94.32 %-100%, and compared with the rates before spraying, all the differences were statistically significant (all P < 0.01). The unit costs per 1 m2 of the molluscicide abovementioned were ranged from 0.280 Yuan to 0.416 Yuan. CONCLUSIONS: In marshland area inside embankment, the molluscicide formulations of the powder and granule are suitable for the environments without water or with instability water level, while the molluscicide formulations of the suspended agents and wettable powder are suitable for the water environment. Though the unit cost of powder is the lowest, the molluscicide in this formulation flies away seriously.

[Analysis of cost-effectiveness of molluscacide combined with herbicide by spraying].

OBJECTIVE: To explore an economical and efficient molluscicidal method suitable for large area of nursery stock field. METHODS: Two nursery stock fields with Oncomelania hupensis were selected as experimental sites, and an experimental group and a control group were set. In the experimental group, the molluscacide and herbicide were alternately used (a purification molluscicidal method) during the period of May to October, 2011. In the control group, grass shoveling and soil burying combined with molluscacide were used in the same period. The snail control effects of the two groups were observed and the costs of the two methods were analyzed. RESULTS: No living snails were found in both experimental and control groups three consecutive years after the snail control intervention above mentioned. The costs of snail control intervention in the experimental group and control group were 0.90 and 1.80 Yuan/m2, respectively. CONCLUSION: The effect of the purification molluscicidal method in nursery stock field is satisfying, and the cost is lower.

[Molluscicidal effect and cost-effectiveness of suspension concentrate of metaldehyde and niclosamide in the field in Honghu City].

OBJECTIVE: To assess the molluscicidal effect and cost-effectiveness of suspension concentrate of metaldehyde and niclosamide (MNSC) in the field, so as to evaluate the possibility of popularization and application value. METHODS: 26% MNSC and 50% wettable powder of niclosamide (WPN) were used for Oncomelania snail control with the spraying method in the field, and the 15-d molluscicidal effects and costs were investigated. RESULTS: Fifteen days after the spraying, in the beach of Dongjing River, the snail death rates of MNSC and WPN were 89.40% and 88.08%, respectively, and the density reduction rates of MNSC and WPN were 92.35% and 91.67%, respectively. In the marshland of Honghu Lake, the snail death rates of MNSC and WPN were 86.59% and 87.01%, respectively, and the density reduction rates of MNSC and WPN were 90.05% and 91.71%, respectively. There was no significant difference in the molluscicidal effect between two drugs (P > 0.05). The cost of MNSC used in 100 m2 was 15.03 Yuan, while the cost of WPN used in 100 m2 was 16.29 Yuan. CONCLUSION: MNSC has high molluscicidal efficacy, low cost and low impact on environments, which possesses of popularization and application value in the field.

[Evaluation of molluscicidal effects of contracted responsibility system in Changshan County].

OBJECTIVE: To explore a new molluscicidal pattern suitable for the complicated environments in hilly regions, so as to provide the evidence for making the strategy of Oncomelania snail control. METHODS: The contracted responsibility system for snail control was implemented by government. The quality of control work was evaluated in the same year and the recent molluscicidal effect was assessed in the next spring. RESULTS: After the intervention, the decline rate of snail areas increased from 53.4% to 100%; the compression rate of snail spots increased from 54.6% to 100%; the input of fund for snail control decreased from 2.03 Yuan/m2 to 0.69 Yuan/m2; the cost of snail control decreased from 3.73 Yuan/m2 to 0.75 Yuan/m2; the work efficiency increased from 12.0 m2/(man x day) to 36.7 m2/(man x day); the molluscicide decreased from 7.50 tons/year to 3.20 tons/year and the decline rate was 57.3%. The awareness rate and recognized rate of the contracted responsibility system for snail control were both 92.5%. CONCLUSION: The contracted responsibility system for snail control can increase financing efficiency, molluscicidal quality and work efficiency, and save molluscicide in complicated environments of hilly regions.

[Effect and cost-benefit of Oncomelania snail control by plowing and planting in Jiaobei Beach of Zhenjiang City].

OBJECTIVE: To evaluate the effect and cost-benefit of Oncomelania snail control by plowing and planting in Jiaobei Beach of Zhenjiang City. METHODS: In 2009, the measures of building low dike and plowing and planting were implemented in the experimental area of the east part of Jiaobei Beach, while in the control area of the west part of the beach, the molluscacide (niclosamide) was used to control snails. Then, the snail control effects and the cost-benefits of the two groups were compared. RESULTS: In the experimental area, the density of living snails decreased by 99.75% in the year when the measures were implemented, and no living snails were found from the second year. Though that the density of living snails in the control area decreased by 70% around, it aroused again in the second year. The net cost-benefit ratios of the experimental area and the control area were 2.18 and -0.92, respectively. CONCLUSION: Building low dike and plowing and planting in the beaches along the middle and lower reaches of the Yangtze River can effectively control snails, meanwhile, it is economic.

Achievement of the World Bank loan project on schistosomiasis control (1992-2000) in Hubei province and the challenge in the future.

Since the World Bank provided a loan for control of schistosomiasis in China, started from 1992, with the objective of a reduction of prevalence and intensity of the infection both in humans and animals by 40%, through mass chemotherapy in areas of high prevalence, and selective chemotherapy in areas with medium and low endemicity together with focal mollusciciding, the objective of morbidity control of the project has been reached in Hubei Province.