[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.

[Assessment of risk factors of schistosomiasis transmission control in Jingzhou City].

OBJECTIVE: To understand the key risk factors of schistosomiasis transmission in Jingzhou City, so as to provide the evidence for improving the treatment of these risk factors. METHODS: Each village of six counties was investigated and 3 environments were surveyed each village for the distribution of Oncomelania snails and animal stools in the field. The results were analyzed and the risk factors of schistosomiasis transmission were assessed. RESULTS: The density of living snails was 0.43 snails per 0.1 m2, the frequency of the frames with snails was 9.12%, and no schistosome infected snails were found. All of the animal stools collected from the field were from bovines. The schistosome positive rate of animal stools was 37.50% (3/8) among the environments, and the schistosome infection rate of stools was 8.11% (3/37). The schistosome infection rate of animal stools was 0 near the residence living sites, and the positive rates were 12.50% and 8.33% in the ditches and slopes, respectively (chi2 = 0.07, P > 0.05). CONCLUSIONS: Bovine is still the main infectious source of schistosomiasis, i.e. the main risk factor of the disease transmission. Therefore, the strategy of controlling bovine should be strengthened.

[Effect of modified crushing-cercariae escaping method on detection of infected Oncomelania snails in field].

OBJECTIVE: To evaluate the effect of a modified crushing-cercariae escaping method on the detection of infected Oncomelania snails in the field. METHODS: A snail survey was carried out in Jingzhou City in the spring of 2011, and the villages were randomly divided into several groups, the coincidence rates, detection rates and the labour cost of the modified crushing-cercariae escaping method and crushing method were compared. RESULTS: A total of 14 snail spots were surveyed, and the coincidence rate of the two methods was 100%. In the spring snail survey, 539 villages and 3 536 spots with snails were detected by the modified crushing-cercariae escaping method, and 671 villages and 11 375 spots with snails were detected by the crushing method. The detection rates of villages with infected snails of the two methods were 25.79% and 28.46%, respectively, the difference between them was not statistically significant (chi2 = 1.079 5, P > 0.05); and those of spots with infected snails were 5.57% and 3.66%, respectively, which had no significant difference between them (chi2 = 95.464 1, P < 0.01). Compared with the crushing method, the modified crushing-cercariae escaping method reduced labour cost by 87.86%, and saved 12.95 person-days per township. CONCLUSION: The modified crushing-cercaria escaping method can identify the spots with infected snails quickly and accurately with less labour cost, therefore, it is suitable for detecting environments with infected snails in batch in endemic areas.

[Environmental distribution and disposal measures of infected Oncomelania snails in Jingzhou City].

A survey of Oncomelania snail distribution was carried out with the systematic sampling method in combination with the environmental sampling method. A questionnaire survey was performed to find out the sites where stool examination-positive patients were infected. The results showed that there were 1 721 infected snail spots in Jingzhou City. Most of infected snail spots (94.1%) were only 500 m far away from the nearest residential areas from 2004 to 2010. About 97% of patients considered that the sites where they were infected with schistosome were only 400 meters far away from their residential areas. In conclusion, the survey with a questionnaire method in patients with positive stool examinations can quickly identify the environments with infected snails.

[Comparative evaluation of models for infectious source control of schistosomiasis in lake and marshland regions].

OBJECTIVE: To compare the effect of different models for the control of infectious source of schistosomiasis, so as to explore the control models suitable for lake and marshland regions. METHODS: The models of "replacement of cattle with machine" and "grazing prohibition and establishing fixed pasture" were implemented in 2 towns of Gong'an and Jianli counties, Hubei Province, respectively, and the data of infection situation of human and livestock, Oncomelania hupensis snail situation and the contamination status of wild faeces were collected and analyzed from 2008 to 2010. RESULTS: In 2010, for the model of "replacement of cattle with machine", the infection rate of residents in the observation group decreased by 56.82% comparing to that in 2008, the difference had a statistical significance (chi2 = 78.197, P < 0.01), and the decrease extent in the observation group was larger than that in the control group; the infection rates of cattle and snails, and the density of infected snails of the former were all decreased to 0. No wild faeces were discovered in the observation group, while 58 pieces of wild faeces were discovered but no schistosome eggs were found in these faeces in the control group. In 2010, for the model of "grazing prohibition and establishing fixed pasture", the infection rate of residents in the observation group decreased by 39.00% without a statistic significance (chi2 = 1.594, P > 0.05), and the infection rate of cattle decreased by 43.98% without a statistically significant difference (chi2 = 0.751, P > 0.05) comparing to those in 2008. The density of living snails decreased by 89.83% in the observation group, while that in the control group increased by 6.80%. A total of 11 pieces of wild faeces were collected in the observation group, with a positive rate of 18.18%, and 7 pieces were collected in the control group, all of which were negative. During the 2 years, no acute and advanced schistosomiasis patients were newly discovered. CONCLUSIONS: "Replacement of cattle with machine" and "grazing prohibition and establishing fixed pasture" are the main measures for schistosomiasis control in lake and marshland regions, the former is suitable for inner embankment regions, while the latter is suitable for the outer-embankment areas.

[Survey of causes of infected Oncomelania snails and infectious sources of schistosomiasis in marshland and lake region of Jingzhou City].

OBJECTIVE: To explore the causes of infected Oncomelania snails and the sources of infection of schistosomiasis in marshland and lake regions of Jingzhou City, so as to provide the evidence for the establishment of control strategy. METHODS: The snail environments in villages with or without cattle in Gong'an and Jianli counties, Hubei Province were selected, the snail status, infection status of people and livestock and wildlife reservoir host (mice), as well as the contamination status of wild faeces were surveyed, and the infectivity of water in investigated villages without cattle were detected by sentinel mice. The correlation between the densities of infected snails and positive faeces were tested by the rank correlation method. RESULTS: In villages without cattle, there were no positive faeces and infected sentinel mice discovered, while in the villages with cattle, 374 pieces of wild faeces were collected, the densities of wild faeces were 0.02 - 0.29 pieces/100 m2, and those of the positive ones were 0 - 0.01 pieces/100 m2, and the densities of infected snails were 0.001 - 0.040 snails /0.1 m2. The distribution of infected snails was consistent with that of the positive faeces, but the correlation coefficient between their densities had no statistical significance (r(s) = 0.123 5, P > 0.05). The average infection rates of human in villages with cattle inside embankment of Gong'an and Jianli counties were 2.87% and 1.37%, respectively, while that of the villages outside embankment of Gong'an County was 1.23%, and all the infection rates of cattle were 0. No infected wild mice were discovered. CONCLUSIONS: Human and cattle are the main sources of schistosome infection in the local areas, the possibility of wild mice as source of infection is low, and cattle is an important cause of infected snails in marshland and lake regions in Jingzhou City.

[Effect of synchronous chemotherapy for residents and livestock against schistosomiasis japonica for 12 years in Jingzhou city].

OBJECTIVE: To evaluate the anti-schistosomiasis effect of World Bank loan for schistosomiasis control project 1992-2001 in Jingzhou City, Hubei Province, and observe the endemic situation after two years of the end of the project. METHODS: By a retrospective longitudinal survey, information from annual reports was collected, which included disease screening, treatment and extended chemotherapy for human population and livestock, the distribution of Oncomelania hupensis and health education information from eight counties in Jinzhou prefecture from 1992 to 2003. Statistical u test was used for phased retrospective dynamic analysis. RESULTS: In the year 2001, schistosomiasis patients (77 009 cases) were 45.2% less than that of 1992 (140438 cases). The number of acute and advanced cases (63 and 1 032 cases, respectively) was 74.2% and 43.9% less than those of 1992 (244 and 1 841 cases, respectively). The average infection rate among residents was also reduced from 7.8% of 1992 to 4.7% (u = 28.864, P < 0.01). Number of infected cattle in 2001(3 454) was 57.0% less than that of 1992 (8 035), and the prevalence in cattle was reduced from 7.9% of 1992 to 3.7%, decreased by 53.2% (u = 9.338, P < 0.01). Snail-ridden area in 2001 was 19 368 hectares, 23.7% less than that of 1992 (25 395 ha). In 2003, two years after end of the project, number of acute schistosome infections was 100 cases, 59.0% less than that of 1992, but 58.7% more than that of 2001. The average infection rate in humans increased to 8.4% in 2003, 7.7% and 78.7% more than that of 1992 and 2001, respectively (u = 6.453, 34.804, P < 0.01). The average infection rate in cattle increased to 6.5% in 2003, 17.7% less than that of 1992, but 75.6% more than that of 2001 (u = 3.061, 5.894, P < 0.01). Snail-ridden areas also increased in 2003 with 29.3% and 69.6% more than that of 1992 and 2001, respectively. CONCLUSION: Synchronous chemotherapy for residents and livestock can reduce the prevalence of schistosomiasis and control its transmission effectively in several year period, but the disease may re-emerge after chemotherapy stopped.

[Sampling survey on schistosomiasis in Jingzhou City in 2006].

A survey on schistosomiasis conducted in sampled 453 out of 1971 villages in Jingzhou City in the year of 2006. Miracidia hatching test demonstrated that the prevalence in human population was 3.9% (12,006/310,232), with sporadic cases of acute schistosomiasis, and the prevalence in cattle was 10.2% (270/2,651). The mean density of living snails was 0.67/0.11 m2 (1,988/1,054,597) with a density of infected snails of 0.001 9/0.11 m2 (1,988/713,486). In comparison to those of 2004, prevalence in humans decreased by 40.0%, prevalence in cattle increased by 22.3%; the snail-ridden area increased by 4.0%, but the mean density of living snails increased by 68.5% and the infected snail density increased by 18.8% with a decrease of 36.4% in snail infection rate. Consequently, there is an urgent need in controlling schistosome infection in cattle.