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Objective To investigate the survival period of Yunnan Province-derived smooth-shelled Oncomelania snails bred in laboratory. Methods Oncomelania snails were sampled from Heqing and Yongsheng counties where schistosomiasis is endemic, and uninfected adult snails were collected and bred in laboratory. The survival period of snails sampled from these two counties was compared. Results The 1-, 2-, 3- and 4-year survival rates of laboratory-bred smooth-shelled snails sampled from Yunnan Province were 72.36%, 29.11%, 13.08% and 0.21%, respectively, and were 74.66%, 38.91%, 19.46% and 0.45% for snails derived from Heqing County, and 70.36%, 20.55%, 7.51% and 0 for snails sampled from Yongsheng County, respectively. The mean and median survival period of Yunnan Province-derived adult snails was 20.90 and 20.67 months, and there were significant differences between the snails sampled from Heqing and Yongsheng counties in terms of the mean (22.94 vs. 19.13 months, P < 0.05) and median survival period (21.63 vs. 19.81 months, P < 0.05). Conclusion The mean survival period of Yunnan Province-derived smooth-shelled adult snails is approximately 20 months in laboratory, and the survival varies in geographical areas.
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OBJECTIVE: To assess the effectiveness of infectious source control at various stages of transmission control of schistosomiasis in Eryuan County of Yunnan Province, so as to provide insights into the further monitoring and management of infectious sources of schistosomiasis. METHODS: Wenbi Village, a plateau subtype region and Qiandian Village, a mountain subtype region in Eryuan County were selected as the study areas. The species, schistosome infection and transmission capability of infectious sources were investigated in Wenbi and Qiandian villages in 2011 and 2018 and were compared. RESULTS: Schistosome infections were detected in human, bovine, horse, dog and mouse in Qiandian Village in 2011, with positive rates of 1.19%, 0.91%, 1.25%, 3.13% and 0.95%, respectively, and human, bovine and dog were found to have schistosome infections, with positive rates of 0.76%, 1.66% and 9.30%, respectively. However, no infections were identified in human, bovine, horse, pig, dog, sheep or mouse in these two villages in 2018. A total of 731 wild feces were collected in both villages in 2011. In Qiandian Village, horse, bovine and dog feces accounted for 34.40%, 29.80% and 20.20% of all fecal samples, and dog and horse feces were found to have schistosome infections (11.94% and 6.90% positive rates, respectively). In Wenbi Village, dog, bovine and human feces accounted for 44.59%, 39.83% and 14.29% of all fecal samples, and dog, human and bovine feces were found to have schistosome infections (16.95%, 9.52% and 2.33% positive rates, respectively). In 2018, a total of 204 wild feces were collected in both villages, and no schistosome infections were identified. Sheep, dog and bovine feces accounted for 36.27%, 33.33% and 27.45% of all fecal samples in Qiandian Village, and dog, bovine and human feces accounted for 72.55%, 11.76% and 10.78% of all fecal samples in Wenbi Village. CONCLUSIONS: A remarkable achievement has been obtained in the control of infectious sources of schistosomiasis in Eryuan County, and the role of human and bovine as the major infectious sources of schistosomiasis has been effectively controlled. In the future, the integrated strategy with emphasis on the control of infectious sources should be intensified, and the management of reservoir hosts including dog and mouse should be strengthened.
Subject(s)
Disease Reservoirs , Schistosomiasis , Animals , Cattle , China/epidemiology , Disease Reservoirs/parasitology , Dogs , Feces/parasitology , Horses , Humans , Mice , Prevalence , Schistosoma , Schistosomiasis/epidemiology , Schistosomiasis/prevention & control , Schistosomiasis/transmission , Sheep , Snails , SwineABSTRACT
In China, the mountainous and hilly schistosomiasis-endemic areas are mainly distributed in 2 provinces of Sichuan and Yunnan. Although great success has been achieved in schistosomiasis control in mountainous and hilly areas, there is a risk of re-emerging schistosomiasis in local areas. Hereby, we described the emergency treatment of two schistosomiasis outbreaks that occurred in transmission-interrupted areas of Yunnan Province in 2011 and 2013, pointed out the risk of schistosomiasis rebounding in mountainous and hilly areas and proposed some suggestions.
Subject(s)
Disease Outbreaks , Emergency Treatment , Schistosomiasis , Animals , China/epidemiology , Humans , Schistosomiasis/drug therapy , Schistosomiasis/epidemiology , Schistosomiasis/prevention & control , Schistosomiasis/transmission , SnailsABSTRACT
A three-level (provincial, municipal and county levels) schistosomiasis diagnosis network platform had been created in Yunnan Province, and assessment of laboratory quality-control samples and field evaluation of nucleic acid diagnostic techniques and immunodiagnostic reagents had been performed. This paper described the review process of the schistosomiasis diagnosis network laboratory and the operation of schistosomiasis diagnosis network laboratory and analyzed the problems of the schistosomiasis diagnosis network laboratory in Yunnan Province. The establishment of the schistosomiasis diagnosis reference (network) laboratory will provide a strong support for schistosomiasis control in Yunnan Province in the new era.
Subject(s)
Laboratories , Schistosomiasis , China , Humans , Laboratories/standards , Schistosomiasis/diagnosisABSTRACT
A three-level (provincial, municipal and county levels) schistosomiasis diagnosis network platform had been created in Yunnan Province, and assessment of laboratory quality-control samples and field evaluation of nucleic acid diagnostic techniques and immunodiagnostic reagents had been performed. This paper described the review process of the schistosomiasis diagnosis network laboratory and the operation of schistosomiasis diagnosis network laboratory and analyzed the problems of the schistosomiasis diagnosis network laboratory in Yunnan Province. The establishment of the schistosomiasis diagnosis reference (network) laboratory will provide a strong support for schistosomiasis control in Yunnan Province in the new era.
ABSTRACT
In China, the mountainous and hilly schistosomiasis-endemic areas are mainly distributed in 2 provinces of Sichuan and Yunnan. Although great success has been achieved in schistosomiasis control in mountainous and hilly areas, there is a risk of re-emerging schistosomiasis in local areas. Hereby, we described the emergency treatment of two schistosomiasis outbreaks that occurred in transmission-interrupted areas of Yunnan Province in 2011 and 2013, pointed out the risk of schistosomiasis rebounding in mountainous and hilly areas and proposed some suggestions.
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Objective To assess the effectiveness of infectious source control at various stages of transmission control of schistosomiasis in Eryuan County of Yunnan Province, so as to provide insights into the further monitoring and management of infectious sources of schistosomiasis. Methods Wenbi Village, a plateau subtype region and Qiandian Village, a mountain subtype region in Eryuan County were selected as the study areas. The species, schistosome infection and transmission capability of infectious sources were investigated in Wenbi and Qiandian villages in 2011 and 2018 and were compared. Results Schistosome infections were detected in human, bovine, horse, dog and mouse in Qiandian Village in 2011, with positive rates of 1.19%, 0.91%, 1.25%, 3.13% and 0.95%, respectively, and human, bovine and dog were found to have schistosome infections, with positive rates of 0.76%, 1.66% and 9.30%, respectively. However, no infections were identified in human, bovine, horse, pig, dog, sheep or mouse in these two villages in 2018. A total of 731 wild feces were collected in both villages in 2011. In Qiandian Village, horse, bovine and dog feces accounted for 34.40%, 29.80% and 20.20% of all fecal samples, and dog and horse feces were found to have schistosome infections (11.94% and 6.90% positive rates, respectively). In Wenbi Village, dog, bovine and human feces accounted for 44.59%, 39.83% and 14.29% of all fecal samples, and dog, human and bovine feces were found to have schistosome infections (16.95%, 9.52% and 2.33% positive rates, respectively). In 2018, a total of 204 wild feces were collected in both villages, and no schistosome infections were identified. Sheep, dog and bovine feces accounted for 36.27%, 33.33% and 27.45% of all fecal samples in Qiandian Village, and dog, bovine and human feces accounted for 72.55%, 11.76% and 10.78% of all fecal samples in Wenbi Village. Conclusions A remarkable achievement has been obtained in the control of infectious sources of schistosomiasis in Eryuan County, and the role of human and bovine as the major infectious sources of schistosomiasis has been effectively controlled. In the future, the integrated strategy with emphasis on the control of infectious sources should be intensified, and the management of reservoir hosts including dog and mouse should be strengthened.
ABSTRACT
A three-level (provincial, municipal and county levels) schistosomiasis diagnosis network platform had been created in Yunnan Province, and assessment of laboratory quality-control samples and field evaluation of nucleic acid diagnostic techniques and immunodiagnostic reagents had been performed. This paper described the review process of the schistosomiasis diagnosis network laboratory and the operation of schistosomiasis diagnosis network laboratory and analyzed the problems of the schistosomiasis diagnosis network laboratory in Yunnan Province. The establishment of the schistosomiasis diagnosis reference (network) laboratory will provide a strong support for schistosomiasis control in Yunnan Province in the new era.
ABSTRACT
In China, the mountainous and hilly schistosomiasis-endemic areas are mainly distributed in 2 provinces of Sichuan and Yunnan. Although great success has been achieved in schistosomiasis control in mountainous and hilly areas, there is a risk of re-emerging schistosomiasis in local areas. Hereby, we described the emergency treatment of two schistosomiasis outbreaks that occurred in transmission-interrupted areas of Yunnan Province in 2011 and 2013, pointed out the risk of schistosomiasis rebounding in mountainous and hilly areas and proposed some suggestions.
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Objective To assess the effectiveness of infectious source control at various stages of transmission control of schistosomiasis in Eryuan County of Yunnan Province, so as to provide insights into the further monitoring and management of infectious sources of schistosomiasis. Methods Wenbi Village, a plateau subtype region and Qiandian Village, a mountain subtype region in Eryuan County were selected as the study areas. The species, schistosome infection and transmission capability of infectious sources were investigated in Wenbi and Qiandian villages in 2011 and 2018 and were compared. Results Schistosome infections were detected in human, bovine, horse, dog and mouse in Qiandian Village in 2011, with positive rates of 1.19%, 0.91%, 1.25%, 3.13% and 0.95%, respectively, and human, bovine and dog were found to have schistosome infections, with positive rates of 0.76%, 1.66% and 9.30%, respectively. However, no infections were identified in human, bovine, horse, pig, dog, sheep or mouse in these two villages in 2018. A total of 731 wild feces were collected in both villages in 2011. In Qiandian Village, horse, bovine and dog feces accounted for 34.40%, 29.80% and 20.20% of all fecal samples, and dog and horse feces were found to have schistosome infections (11.94% and 6.90% positive rates, respectively). In Wenbi Village, dog, bovine and human feces accounted for 44.59%, 39.83% and 14.29% of all fecal samples, and dog, human and bovine feces were found to have schistosome infections (16.95%, 9.52% and 2.33% positive rates, respectively). In 2018, a total of 204 wild feces were collected in both villages, and no schistosome infections were identified. Sheep, dog and bovine feces accounted for 36.27%, 33.33% and 27.45% of all fecal samples in Qiandian Village, and dog, bovine and human feces accounted for 72.55%, 11.76% and 10.78% of all fecal samples in Wenbi Village. Conclusions A remarkable achievement has been obtained in the control of infectious sources of schistosomiasis in Eryuan County, and the role of human and bovine as the major infectious sources of schistosomiasis has been effectively controlled. In the future, the integrated strategy with emphasis on the control of infectious sources should be intensified, and the management of reservoir hosts including dog and mouse should be strengthened.
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OBJECTIVE: To master the Oncomelania hupensis distribution and infection status in the national schistosomiasis surveillance sites of Yunnan Province, so as to provide the evidence for making the control and prevention measures. METHODS: The data of O. hupensis surveillance in the 18 national surveillance sites of Yunnan Province from 2015 to 2017 were collected and analyzed with the descriptive analysis method according to the national schistosomiasis surveillance programme. RESULTS: The total surveillance area was 5 710.94 hm2, the area with O. hupensis snails was 205.69 hm2. The number of surveillance frames was 2 094 553, the occurrence rate of frames with snails was 0.62%, and the density of living snails was 0.025 4 snails/0.1 m2. In the schistosomiasis epidemic controlled areas, the area with snails, the occurrence rate of frames with snails and the density of living snails were all the highest. The snail concentrated distribution areas were the small reservoir, bottomland, paddy field, ditch, and dry land, and the snails mainly distributed in the rice, dry crop, weed and wood vegetation. The number of frames with snails, occurrence rate of frames with snails, total number of snails, number of living snails, and repetition areas with snails presented increasing trends, and however, no schistosome-infected snails were found during the three years. CONCLUSIONS: The O. hupensis snail status is obviously serious in the national schistosomiasis surveillance sites of Yunnan Province. The comprehensive snail control measures should continue to be strengthened, so as to effectively control the spread of the snails and reduce the risk of schistosomiasis outbreaks.
Subject(s)
Gastropoda , Schistosomiasis , Animal Distribution , Animals , China , Disease Reservoirs/statistics & numerical data , Gastropoda/physiology , Population Density , Population Surveillance , Schistosoma , Schistosomiasis/prevention & controlABSTRACT
OBJECTIVE: To analyze the dynamic endemic situation of schistosomiasis in Yunnan Province, and evaluate the effectiveness of the prevention and control interventions. METHODS: Four schistosomiasis heavy endemic villages (each of 4 endemic counties) from 2005 to 2014 and 18 villages (each of 18 counties) in 2015 and 2016 were selected as survey sites. Then, the serological screening and etiological tests were carried out in the residents and floating population. The infection status of the livestock and relevant information of field feces and Oncomelania hupensis snails were surveyed. RESULTS: The serum positive rate was 8.40% to 25.40% in the local residents, and the rate of the female was higher than that of the male, the rates of 30 to 60 year age groups were higher than those of the other age groups, and the rates of peasants were higher. The feces positive rate was 0 to 6.59%, and the corrected infection rate was 0 to 1.67% in the local residents. The serum positive rate was 0 to 25.00% in the floating population. The infection rate in the livestock was 0 to 10.29%, and the main infected animals were the cattle, buffalo, dog, equine and pig. Totally 1 642 feces were tested, and no positives were found. The area with snail habitats was 753.97 hm2, and the density of living snails was 0.013 9 to 0.631 5 snails/0.1 m2. A total of 64 positive snails were found. The snail control rate was 100%. Totally 161 schistosomiasis patients and 269 schistosome-infected animals were treated. CONCLUSIONS: The schistosomiasis epidemic situation has been effectively controlled, and is at a low prevalence status in Yunnan Province. In order to block the transmission of schistosomiasis and eliminate schistosomiasis, the comprehensive control measures should be strengthened continually.
Subject(s)
Endemic Diseases , Schistosomiasis , Adult , Animals , Antibodies, Helminth/blood , Cattle , China , Endemic Diseases/prevention & control , Endemic Diseases/statistics & numerical data , Feces/parasitology , Female , Horses , Humans , Male , Middle Aged , Population Surveillance , Prevalence , Schistosoma , Schistosomiasis/epidemiology , Schistosomiasis/prevention & control , Snails/parasitology , SwineABSTRACT
Objective To master the Oncomelania hupensis distribution and infection status in the national schistosomiasis surveillance sites of Yunnan Province, so as to provide the evidence for making the control and prevention measures. Methods The data of O. hupensis surveillance in the 18 national surveillance sites of Yunnan Province from 2015 to 2017 were collected and analyzed with the descriptive analysis method according to the national schistosomiasis surveillance programme. Results The total surveillance area was 5 710.94 hm2, the area with O. hupensis snails was 205.69 hm2. The number of surveillance frames was 2 094 553, the occurrence rate of frames with snails was 0.62%, and the density of living snails was 0.025 4 snails/0.1 m2. In the schistosomiasis epidemic controlled areas, the area with snails, the occurrence rate of frames with snails and the density of living snails were all the highest. The snail concentrated distribution areas were the small reservoir, bottomland, paddy field, ditch, and dry land, and the snails mainly distributed in the rice, dry crop, weed and wood vegetation. The number of frames with snails, occurrence rate of frames with snails, total number of snails, number of living snails, and repetition areas with snails presented increasing trends, and however, no schistosome-infected snails were found during the three years. Conclusions The O. hupensis snail status is obviously serious in the national schistosomiasis surveillance sites of Yunnan Province. The comprehensive snail control measures should continue to be strengthened, so as to effectively control the spread of the snails and reduce the risk of schistosomiasis outbreaks.
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Objective To master the Oncomelania hupensis distribution and infection status in the national schistosomiasis surveillance sites of Yunnan Province, so as to provide the evidence for making the control and prevention measures. Methods The data of O. hupensis surveillance in the 18 national surveillance sites of Yunnan Province from 2015 to 2017 were collected and analyzed with the descriptive analysis method according to the national schistosomiasis surveillance programme. Results The total surveillance area was 5 710.94 hm2, the area with O. hupensis snails was 205.69 hm2. The number of surveillance frames was 2 094 553, the occurrence rate of frames with snails was 0.62%, and the density of living snails was 0.025 4 snails/0.1 m2. In the schistosomiasis epidemic controlled areas, the area with snails, the occurrence rate of frames with snails and the density of living snails were all the highest. The snail concentrated distribution areas were the small reservoir, bottomland, paddy field, ditch, and dry land, and the snails mainly distributed in the rice, dry crop, weed and wood vegetation. The number of frames with snails, occurrence rate of frames with snails, total number of snails, number of living snails, and repetition areas with snails presented increasing trends, and however, no schistosome-infected snails were found during the three years. Conclusions The O. hupensis snail status is obviously serious in the national schistosomiasis surveillance sites of Yunnan Province. The comprehensive snail control measures should continue to be strengthened, so as to effectively control the spread of the snails and reduce the risk of schistosomiasis outbreaks.
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Objective To analyze the dynamic endemic situation of schistosomiasis in Yunnan Province,and evaluate the effectiveness of the prevention and control interventions.Methods Four schistosomiasis heavy endemic villages(each of 4 en-demic counties)from 2005 to 2014 and 18 villages(each of 18 counties)in 2015 and 2016 were selected as survey sites.Then,the serological screening and etiological tests were carried out in the residents and floating population.The infection status of the livestock and relevant information of field feces and Oncomelania hupensis snails were surveyed.Results The serum positive rate was 8.40％to 25.40％in the local residents,and the rate of the female was higher than that of the male,the rates of 30 to 60 year age groups were higher than those of the other age groups,and the rates of peasants were higher.The feces positive rate was 0 to 6.59％,and the corrected infection rate was 0 to 1.67％in the local residents.The serum positive rate was 0 to 25.00％in the floating population.The infection rate in the livestock was 0 to 10.29％,and the main infected animals were the cattle,buffa-lo,dog,equine and pig.Totally 1 642 feces were tested,and no positives were found.The area with snail habitats was 753.97 hm2,and the density of living snails was 0.013 9 to 0.631 5 snails/0.1 m2.A total of 64 positive snails were found.The snail con-trol rate was 100％.Totally 161 schistosomiasis patients and 269 schistosome-infected animals were treated.Conclusions The schistosomiasis epidemic situation has been effectively controlled,and is at a low prevalence status in Yunnan Province.In order to block the transmission of schistosomiasis and eliminate schistosomiasis,the comprehensive control measures should be strengthened continually.
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OBJECTIVE: To master the prevalence status of schistosomiasis in Yunnan Province in 2016, so as to provide the evidence for formulating the control strategy and intervention measures. METHODS: The schistosomiasis heavy-endemic villages were selected from each of 18 endemic counties as the survey sites. Then, the serological and etiological tests were carried out in the local residents and floating population, and the infection status of the livestock, field feces and Oncomelania hupensis snails were surveyed. RESULTS: The serum positive rate of schistosomiasis of local residents was 8.78% and the serum positive rate was 2.26% of floating population. No schistosome eggs were found in the stool examinations in the population. The area with snails was 80.054 6 hm2 in 2016 with an increasing rate of 45.47% compared to that in 2015. The average density of living snails was 0.031 7/0.1 m2. No schistosome-infected snails were found for the last four years and no new area with snails was found for the last three years. No positive livestock or feces were found. CONCLUSIONS: The schistosomiasis epidemic situation is stabilized in Yunnan Province in 2016. However, the area with snails and the number of living snails are increasing, and therefore, the schistosomiasis epidemic risk still exists. So, the comprehensive control measures should be strengthened continuously.
Subject(s)
Schistosomiasis/epidemiology , Animals , China/epidemiology , Feces/parasitology , Humans , Livestock/parasitology , Parasite Egg Count , Schistosoma , Snails/parasitologyABSTRACT
OBJECTIVE: To evaluate the effect of hydraulic schistosomiasis control project with ditches managed on Oncomelania hupensis snail control. METHODS: From 2009 to 2011, the snail investigations and schistosomiasis surveillance were carried out in Dali City and Yongsheng County, two sites of national schistosomiasis surveillance. The history data of schistosomiasis control were collected and analyzed. RESULTS: At the harden sections of the water conservancy project with ditches managed in Shajing Village of Dali City, only one snail was found in 2010 with the density of living snails of 0.004 snails/0.1 m2, while the densities of living snails were respectively 0.080, 0.002 snails/0.1 m2 and 0.007 snails/0.1 m2 in unhardened sections of the project from 2009 to 2011. No snails were found in the harden sections of the water conservancy project with ditches managed in Gaojiacun Village of Yongsheng County, while the densities of living snails were respectively 0.040, 0.030 snails/0.1 m2 and 0.040 snails/0.1 m2 in unhardened sections of the project from 2009 to 2011. After the ditches were hardened, no infected snails were found from 2009 to 2011, and the appearance rate of frames with snails and density of living snails were both decreased, while they were both higher in unhardened ditches. CONCLUSIONS: The hydraulic schistosomiasis control project has obvious effect on control snails, but the maintain work should be strengthened after the project is completed.
Subject(s)
Disease Reservoirs/parasitology , Schistosomiasis/transmission , Snails/parasitology , Animals , China/epidemiology , Humans , Schistosomiasis/epidemiology , Schistosomiasis/parasitology , Schistosomiasis/prevention & control , Snails/physiology , Water/parasitology , Water ResourcesABSTRACT
OBJECTIVE: To carry out the surveillance with sentinel mice in the key water areas of schistosomiasis endemic regions in Yunnan Province, so as to establish and perfect the surveillance and forecast system of schistosomiasis. METHODS: Six villages of three counties with schistosomiasis heavy endemic status were selected as the survey points. Then, the surveillance and forecast with the sentinel mice were carried out in the key water areas in the survey points. The recovered sentinel mice were dissected in laboratory, and their serum antibodies against schistosome were detected. Meanwhile, the suspicious infested water contacts of the residents and livestock in the surveillance sites were investigated, and the endemic data of schistosomiasis in the survey points in recent 3 years were collected and analyzed. RESULTS: Totally 282 sentinel mice were placed in the water area, 252 were recovered, with a recovery rate of 90.78%, and 8 mice were dead, with a mortality rate of 3.13%. The number of mice with schistosome egg granuloma and adult worm detected were both 0, and the worm burden and the positive rate of serum antibodies against schistosome were both 0, too. The persons who contacted with the suspicious infested water were mainly villagers and students by harvesting and playing. The Oncomelania hupensis snail areas, the infection rates of residents and livestock were obviously declined in recent 3 years. CONCLUSIONS: There are no positive sentinel mice found in the key water areas of the surveillance sites in Yunnan Province, which suggests that the schistosome infection risk of residents and livestock is low. However, the comprehensive control measures, surveillance and forecast with sentinel mice in the key water areas of schistosomiasis endemic regions still should be strengthened.
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OBJECTIVE: To evaluate and compare the short-term effects of two kinds of plastic mulch on Oncomelania hupensis snail control in irrigation and drainage ditches with snails in Yunnan Province. METHODS: The irrigation and drainage ditches with high density of Oncomelania hupensis snails were chosen as the investigation sites, and then 4 groups were set, namely a colorless plastic mulch group, black plastic mulch group, colorless plastic mulch with molluscicide group and black plastic mulch with molluscicide group. The snail situation of the 4 groups was surveyed before the experiment and 7, 14, 21, 30 days after covering plastic mulch, and the snail death rates were compared among the 4 groups. Meanwhile, the hourly temperatures of soil surface, soil surface under plastic mulch and soil layer 5, 15 cm under the surface as well as the weather situation during the study period were measured and recorded. RESULTS: The average snail mortality rate of the colorless plastic mulch group was only 15.29% that was higher than that of the black plastic mulch group (6.56%) (P < 0.01). The average snail mortality rates of the colorless and black plastic mulch with molluscicide groups were 40.80% and 50.15%, respectively, and there was no statistic difference between them (P > 0.05). Both kinds of plastic mulches could raise the temperature of the soil surface under plastic mulch and the soil layer below it, and the temperature of soil under the mulches increased over the cover time, and the average temperature of the soil surface under the black mulch in 30 days was higher than that under the colorless mulch. CONCLUSIONS: It is not suitable to use plastic mulch only in irrigation and drainage ditches with snails widely in Yunnan Province because of its low effect, and if necessary, the molluscicide should be added.
