[Development and application of Jingcen DY-1 spraying tanker for Oncomelania hupensis snail control].

OBJECTIVE: To develop a Jingcen DY-1 type spraying tanker for Oncomelania hupensis snail control and evaluate its effect of field application as well as the cost. METHODS: The currently available tractor was used as a vector, and the mechanical and electrical equipments and containers were integrated with shafts, pipelines and electric lines to produce a spraying tanker for snail control, with the functions of carrying people and molluscicides, generating electric power and getting water, mixing stocking solutions, adjusting molluscicide solutions evenly, and spraying drugs. The volume of the molluscicide solution, flow rate of water injection, and the flow rate, range and advance speed of the spray gun were tested, and the solution concentrations of molluscicide in the tanker and at the muzzle of the spray gun at different time were detected. Meanwhile, the molluscicidal effect and cost of the spraying tanker were analyzed by the field test. RESULTS: The volume of the liquid storage pot of the Jingcen DY-1 type spraying tanker was 1 800 L, the flow rate of water injection was 400 L/min, the flow rate and the spray range of the standard spray gun were 110-200 L/min and 19.70-23.50 m, respectively, the efficiency of drug spraying of the spraying tanker was 6 000 m/h, and the ratio of spray width (m) to march speed (m/min) was 1:200. When 5 min post mother liquid recirculating, the average concentration of the molluscicide at the upper-, middle- and lower-layers of the liquid storage pot was (1030.39 ± 43.00) mg/L, with a variation coefficient of 4.17%. The average concentration of the molluscicide in the spraying process (spraying for 2, 4, 6, 8, 9 min) was (953.00 ± 68.87)mg/L, with a variation coefficient of 7.22%. The concentration of the residual drug in the liquid storage pot post spraying was 1 000.43 mg/L, which reached the effect concentration for snail control. After spraying for 7 days in the field, the average density of living snails reduced by 88.20% as compared to that before spraying, and the adjusted mortality of snails was 87.65%. The unit cost of Jingcen DY-1 spraying tanker was 0.086 7 Yuan/m². which reduced by 58.20% as compared to that of the conventional spraying tanker. CONCLUSIONS: Jingcen DY-1 type spraying tanker for snail control which integrates various equipments together can effectively control the concentration and dose of the molluscicide, and the machine is labor-saving, efficient, economic and well adapted, and is worthy to be widely applied.

[Application effect of Oncomelania hupensis snail crushers in batch detection].

OBJECTIVE: To evaluate the application effect of Oncomelania hupensis snail crusher in batch detection. METHODS: The O. hupensis snail crushers and triangular flasks for cercariae shedding were made. The uninfected snails were divided into 4 groups with the snail number of 50, 100, 200, 300, respectively, and then they were put in 40 triangular flasks, 10 flasks each group. Three flasks in each group were randomly selected, and 12 schistosome infected O. hupensis snails were put into the flasks (1 snail per flask). The 12 flasks with infected O. hupensis snails were put back to each group and were numbered uniformly. The O. hupensis snails in each group were crushed by the O. hupensis snail crushers, and the crushing rate of snails, and average crushing time and duration were recorded. When all the O. hupensis snails were crushed, water was added into the flasks, and water films from each flask were taken and observed under microscopes, the number of cercariae was recorded and the detection rates of each group were calculated. Meanwhile, the O. hupensis snails in the field were collected and detected by the crushing method and crushing and shedding method with O. hupensis snail crushers, and the coincidence rate of the two methods was calculated. RESULTS: The crushing rate of snails in all the 4 groups were 100% , the average crushing times of groups with 50, 100, 200, 300 snails were 15.70, 23.20, 32.20, 39.20, respectively, and the average duration was 1.01, 1.70, 2.00, 3.00 min, respectively. Both the crushing time and duration were positively correlated with the number of snails detected (r = 0.68, 0.73, both P <0.01). The detection rates of cercariae in all the 4 groups were 100%. In the field application, 109 snails were detected by the crushing method, 620 ones were detected by the crushing and shedding method with O. hupensis snail crushers, and no infected snails were found, the coincidence rate of the two methods were 100%. CONCLUSION: The O. hupensis snail crusher with the advances of easy operation and labor-saving is valuable of field promotion.

[Effect of schistosomiasis control in Jingzhou City from 2009 to 2013].

OBJECTIVE: To evaluate the effect of schistosomiasis control in Jingzhou City of Hubei Province from 2009 to 2013, so as to provide the reference for the establishment of control strategy in the future. METHODS: The annual reports on schistosomiasis control from 2009 to 2013 in nine counties (cities, districts) in Jingzhou City were collected and analyzed sta- tistically. RESULTS: The estimated number of schistosomiasis patients in Jingzhou City dropped from 78 903 in 2009 to 28 034 in 2013, with a reduction rate of 63.37%. The schistosome infection rate of residents dropped from 2.21% in 2009 to 0.65% in 2013, which showed an exponential decline trend (y = 3.196e(-0.317x)). The number of cattle with schistosomiasis decreased from 2 132 in 2009 to 0 in 2013, and the infection rate of cattle dropped from 1.87% in 2009 to 0% in 2013. Only 2 cases with acute infection of schistosome were found in 2009, and no schistosome infected snails were found out in 2 consecutive years, 2012 and 2013. CONCLUSIONS: The endemic level of schistosomiasis in Jingzhou City has decreased significantly. In order to consolidate the achievement of control, the comprehensive strategy including infection source control, snail control with mol- luscicides and snail surveillance should be implemented.

[Investigation on field feces in schistosomiasis endemic areas in Jingzhou City].

OBJECTIVE: To understand the status of field feces in Jingzhou City, so as to provide the evidence for improving the control measures to interrupt the transmission routes of schistosomiasis. METHODS: The distribution of field feces was investigated in 27 schistosomiasis endemic villages in Gong' an, Jianli, Jiangling, Honghu and Shishou counties (cities) from 2010 to 2012. The schistosome positive status of the field feces was surveyed with the hatching method. RESULTS: There were 1366 field feces and the average density was 0.0892 feces per 100 square meters in this survey. The cattle feces, human feces, dog feces and elk feces respectively accounted for 99.71%, 0.07%, 0.15% and 0.07% in the survey. The infection rates of the field feces were 1.46% and 2.42% in the channels and bottomlands, respectively (P > 0.05). The average rate of infected field feces was 3.21% in 2010, 0.36% in 2011, and 1.60% in 2012, and the difference between 2010 and 2012 was not statistically significant (P > 0.05). CONCLUSIONS: The main field feces come from cattle, and the main distribution of infected field feces is in channels and bottom-lands. Therefore, the management of cattle and treatment of field feces should be strengthened.