[The Molluscicidal Effect of Chlorosalicylicamide Sustained-release Granules on Oncomelania hupensis].

Objective: To evaluate the molluscicidal effect of the chlorosalicylicamide sustained-release granules (LDS-SRG) on Oncomelania hupensis. Methods: Seven effective concentrations or dosages of LDS-SRG, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 and 6.4 mg/L （for immersion test） or g/m2（for spraying test）, were prepared from the original 5% and 10% concentrations or dosages in the laboratory. In the immersion test, each concentration of LDS-SRG was incubated with 3 packs of snails（30 snails in each pack）, and each pack was taken for snail counting at 24, 48 and 72 h respectively. In the spraying test, each dosage of LDS-SRG was applied to 200 snails, and the snail mortality was calculated in 50 randmoly collected snails on days 3 and 7, and in the whole on day 14 after administration. In the field immersion test, LDS-SRG at concentrations of 0.4, 0.8 and 1.6 g/m3 was incubated with 6 packs of snails （30 snails in each pack）, and each 2 packs were taken at 24, 48, and 72 h to calculate the snail mortality. In the field spraying test, 0.8, 1.6 and 3.2 g/m2 LDS-SRG was sprayed in 3 snail-positive ditches （～100 m2）, and 10 boxes of snails were selected in each ditch on days 3, 7 and 14 to calculate the snail mortality. The 50% wettable powder of niclosamide ethanolamine salt （WPN） with effective concentrations or dosages of 1.0 mg/L （or g/m2 and g/m3） was used as the positive control. Fresh water served as the blank control. Results: In the labratory immersion test using the original concentration of 5%, both 0.1-6.4 mg/L LDS-SRG for 72 h and 1.6-6.4 mg/L LDS-SRG for 48 h caused 100% mortality; and the concentration lethal to 50% （LC50） at 24, 48 and 72 h was 0.70, 0.01 and 0.01 mg/L respectively. When using the original concentration of 10%, both 0.1-6.4 mg/L LDS-SRG for 72 h and 0.2-6.4 mg/L LDS-SRG for 48 h caused 100% mortality; and the LC50 at 24, 48 and 72 h was 0.15, 0.01 and 0.01 mg/L respectively. The labratory spraying test showed that 7-day administration of 1.6 and 6.4 g/m2 LDS-SRG as well as 14-day administration of 3.2 and 6.4 g/m2 LDS-SRG prepared from 5% dosage, resulted in a snail mortality>95%, with the LD50 on days 3, 7 and 14 being 0.06, 0.16, and 0.18 g/m2; 14-day administration of 1.6 g/m2 LDS-SRG as well as 7-day administration of 6.4 g/m2 LDS-SRG prepared from 10% dosage, resulted in a snail mortality>95%, with the LD50 on days 3, 7 and 14 being 3.29, 0.75, and 0.16 g/m2. The mortality by various dosages of LDS-SRG prepared from 5% dosage was significantly higher than that of the control group (P<0.05). In the field immersion test, the snail mortality by 1.6 g/m3 LDS-SRG prepared from 5% and 10% concentrations for 72 h was 96.43% and 98.21% respectively (P>0.05 versus the control group). In the field spraying test, the snail mortality by 3.2 g/m2 LDS-SRG prepared from 5% dosage for 3, 7 and 14 days was 93.99%, 91.18% and 86.48% respectively, and that from 10% dosage was 94.95%, 93.50% and 85.43%, all significantly higher than that of the control group （82.83%, 72.38% and 48.38%）（P<0.05）; the snail mortality by 0.8 g/m2 LDS-SRG prepared from 5% dosage for 14 days（66.51%） and that by 1.6 g/m2 LDS-SRG prepared from 5% dosage for 3 days（84.61%） were both significantly higher than that by 10% LDS-SRG（20.13% and 43.06%） （P<0.05）. Conclusion: The 5% and 10% LDS-SRG used separately in the immersion test and the spraying test both meet the requirements of the national standard of Efficacy Test Methods and Evaluation of Molluscicide for Pesticide Registration.

[Longitudinal observations on effect of schistosomiasis control in Gongan County, Hubei Province].

OBJECTIVE: To evaluate the effect of schistosomiasis control in Gongan County, Hubei Province by longitudinal observations so as to provide the evidence for formulating the schistosomiasis control strategy in lake and marshland regions. METHODS: The schistosomiasis epidemic data in Gongan County from 2000-2013 were collected by the retrospective research method, and analyzed about the changing tendency of human and cattle infection rates, and Oncomelania hupensis snail situation. RESULTS: The tendency of schistosomiasis epidemic situation was descended from 2000 to 2013. The human infection rate declined from 12.62% in 2000 to 0.69% in 2013. The decline scope of human infection rate was 24.1% in the first stage, 64.4% in the second stage, and 73.0% in the third stage. Eight acute schistosomiasis cases were reported in the first stage, 15 cases in the second stage, and none in the third stage. The cattle infection rate declined from 6.50% in 2000 to 0.30% in 2013. The rise scope of cattle infection rate was 74.2% in the first stage, but the decline scope was 75.0% in the second stage and 87.6% in the third stage. All the cattle were disposal at the end of 2013. The infection rate of snails, area with infected snails, and average density of living snails in the first stage increased by 18.1%, 46.0% and 7.6%, respectively. The 3 indexes above-mentioned in the second stage decreased by 76.8%, 97.8% and 37.9%, respectively. In the third stage, the infection rate of snails and area with infected snails decreased by both 100%, but the average density of living snails increased by 2.7%. The infected snails were found from 2000 to 2011, but none in 2012 and 2013. The infection rate of snails and area with infected snails dropped yearly, the infection rate of snails declined from 0.0007% in 2000 to 0.0002% in 2011, and the area with infected snails declined from 267.8 hm2 in 2000 to 6.37 hm2 in 2011. CONCLUSION: After the implementation of the integrated schistosomiasis prevention and control strategy with the emphasis on infectious source control, the human and cattle schistosome infection rates decline significantly. Hereafter, it is necessary to prevent the schistosomiasis epidemic outbreak or rebound.

[Schistosomiasis endemic situation at a national surveillance site in Gong'an County, Hubei Province from 2004 to 2013].

OBJECTIVE: To understand the schistosomiasis endemic situation at a national surveillance site in Gong'an County, Hubei Province. METHODS: According to The Scheme of Schistosomiasis Surveillance in China, the schistosome infection rates of residents and cattle, and the Oncomelania hupensis snail status were investigated yearly in Zhangjiahu Village, a national surveillance site, in Gong' an County from 2004 to 2013. RESULTS: From 2004 to 2013, the human schistosome infection rates decreased from 10.66% to 0.58%, and the cattle schistosome infection rates from 12.75% to 0. Meanwhile, the snail areas and densities reduced, and the schistosome infected snails were eliminated. CONCLUSION: The schistosomiasis endemic situation declined dramatically at the surveillance site, and schistosomiasis is well-controlled.