ABSTRACT
Objective To investigate the changes in the endemic situation of schistosomiasis in national surveillance sites of Sichuan Province, so as to provide the scientific evidence for formulating the schistosomiasis elimination strategy. Methods From 2015 to 2019, 63 national schistosomiasis surveillance sites were assigned in Sichuan Province, in which Schistosoma japonicum infections were monitored in humans, livestock, wild feces and snails. The monitoring data were descriptively analyzed. Results A total of 94 119 person-time local residents were serologically screened for S. japonicum infections in 63 national surveillance sites of Sichuan Province from 2015 to 2019, with sero-prevalence rates ranging from 1.28% to 3.11%, and the sero-positives were predominantly detected in local residents at ages of over 50 years and in farmers. A total of 94 119 person-time mobile populations were serologically screened for S. japonicum infections in the national surveillance sites during the 5-year period, with sero-prevalence of 1.10% to 1.59%. There were no egg-positives identified in either local residents or mobile populations. Among the 6 126 herd-time livestock detected, no egg-positives were identified, and no S. japonicum infection was detected in the 205 wild feces. Snail survey was performed covering an area of 8 484.08 hm2, and 724.80 hm2 snail habitats were identified, including 2.43 hm2 emerging snail habitats and 63.00 hm2 re-emerging snail habitats. The mean occurrence of frames with snails was 6.87% to 19.63%, and the mean density of living snails was 0.18 to 0.62 snails/0.1 m2 in the national surveillance sites of Sichuan Province from 2015 to 2019; however, no S. japonicum infection was detected in snails. Conclusions The endemic situation of schistosomiasis has reduced to the lowest level in Sichuan Province; however, there is a rise in snail habitats, and there is still a risk of schistosomiasis resurgence. Further improvements of the surveillance system for schistosomiasis are required to achieve the goal of schistosomiasis elimination in Sichuan Province as soon as possible.
ABSTRACT
Objective To analyze the risk of re-emergence of Oncomelania snail(O.snail) from 2015 to 2019, in order to improve the effectiveness of snail control. Methods Collection of report forms and schistosomiasis surveillance data was carried out from 2015 to 2019, and analyzed retrospectively. Results The area of snail-emergence was 6 241.98 hm2 during 2015-2019, 44.29、4 610.18、813.92、446.09 and 327.50 hm2 respectively, for each corresponding year.Among the re-emergence areas, flat-ground subtype was 1 185.49 hm2(18.99%), hilly subtype was 2 536.58 hm2(40.64%), and mountain subtype was 2 519.91 hm2(40.37%).The top 5 cities with O.snail re-emergence areas were Liangshanzhou(2016), Ya′an(2016), Deyang(2016), Meishan(2016), and Meishan(2017).The top 5 disticts with O.snail re-emergence areas were Renshou, Puge, Lushan, Tianquan and Dechang. Conclusion The re-emergence of O.snail attributes to several factors, such as low quality of annual snail survey, unitary method of elimination and complexity of snail habit environment.Surveillance and supervision on the sources of infection and snail spreading should continue with exploration of new method in eliminating snails especially in hilly regions.
ABSTRACT
Objective To investigate the epidemic factors of schistosomiasis in wetlands in Sichuan Province, so as to provide scientific evidence for the prevention and control of schistosomiasis in wetlands. Methods The artificial and natural wetlands were selected from Sichuan Province, and the relevant data regarding wetlands were collected. Routine snail survey, investigation on human morbidity due to schistosomiasis, snail diffusion experiments, questionnaire survey, determination of water infectivity and retrospective survey were conducted. Results In Sichuan Province, the mean densities of living snails were 0.003 snails/0.1 m2 and 2.033 snails/0.1 m2 in the upper and lower reaches of the Meiwan Reservoir wetlands, 0.08 snails/0.1 m2 in the Jinyan Lake of Guanghan City, 0.21 snails/0.1 m2 in Muhe River of Guanghan City, and 0.02 snails/0.1 m2 prior to the construction of Qiong-hai wetland park in Xichang City in 2015. Artificial simulation experiments showed that the largest distance of snail diffusion in water was 2 000 m. There were 8.80% (41/466) of subjects that lived neighboring wetlands, worked in wetlands and visited wet-lands having infested water contact behaviors. A total of 690 sentinel mice were assigned, and no Schistosoma japonicum infection was detected in the 677 mice dissected. Retrospective survey showed that the construction of the Meiwan Reservoir caused the spread of schistosomiasis in Dailing County, and snails were found in the ditches entering the Jinyan Lake and in Jinyan Lake areas 5 years following the construction of the Jinyan Lake in Guanghan City, with S. japonicum -infected snails detected in the ditches entering the Jinyan Lake. Conclusions O. hupensis snails are found in some wetlands in Sichuan Province. Protection of wetlands and snail control with environmental improvements are recommended for the prevention of snail importation in natural wetlands, while in artificial wetlands, thorough snail control is recommended during the construction of the wetlands because of the likelihood of snail importation via water systems. In addition, both natural and artificial wetlands require long-term systematic surveillance of schistosomiasis.
ABSTRACT
Objective To build a schistosomiasis transmission risk surveillance system in Sichuan Province, so as to provide technical support for facilitating the progress towards schistosomiasis elimination in the province. Methods The surveillance sites for schistosomiasis transmission risk were assigned in 63 endemic counties (districts) of 11 cities (prefectures) in Sichuan Province. During the period from 2015 through 2018, wild feces contamination, the sources of Schistosoma japonicum infections (fever patients, livestock and wild animals), water infectivity in key settings, snail distribution in key settings, and snail breeding risk (snail importation and spread, floating debris carrying snails and snail breeding in ecological wetlands) were monitored in the surveillance sites. Results From 2015 to 2018, a total of 1 636 wild faces were detected in Sichuan Province, and 3 faces were positive for S. japonicum, with a 0.18% positive rate; among 3 995 livestock and 59 wild mice monitored, no S. japonicum infection was detected. A total of 49 414 fever patients were monitored in 2018, and 493 were seropositive for S. japonicum infection; then, 445 seropositives were subjected to stool examinations, and no egg-positives were found. From 2010 to 2018, a total of 93 sentinel sites were assigned, and 3 994 sentinel mice were placed for monitoring the water infectivity, with one S. japonicum-infected mouse detected. Between 2015 and 2018, a total of 4 156 key settings were investigated covering an area of 1 998.46 hm2, and 668 settings were detected with snails (16.07%), covering an area of 193.26 hm2; 497 suspected settings with a likelihood of snail importation with plant introduction were monitored from 2017 to 2018, and 65 settings with snails were found with 2 673 snails captured; 593 sites were assigned to collect the floating debris from 2017 to 2018, and 9 191.39 kg floating debris were collected with 186 snails captured; 4 wetlands were monitored for the risk of schistosomiasis transmission from 2013 to 2015, and snail breeding was found in 2 wetlands. No S. japonicum infection was identified in snails captured from all surveillance sites. Conclusions A sensitive and effective schistosomiasis transmission risk surveillance system has been successfully established in Sichuan Province. There is still a risk of schistosomiasis transmission risk in local areas of Sichuan Province. Therefore, the integrated schistosomiasis control measures with emphasis on the control of the source of S. japonicum infections should be further intensified, and snail monitoring and control and monitoring and control of schistosomiasis in wetlands should be also intensified.
ABSTRACT
Objective To investigate the epidemic factors of schistosomiasis in wetlands in Sichuan Province, so as to provide scientific evidence for the prevention and control of schistosomiasis in wetlands. Methods The artificial and natural wetlands were selected from Sichuan Province, and the relevant data regarding wetlands were collected. Routine snail survey, investigation on human morbidity due to schistosomiasis, snail diffusion experiments, questionnaire survey, determination of water infectivity and retrospective survey were conducted. Results In Sichuan Province, the mean densities of living snails were 0.003 snails/0.1 m2 and 2.033 snails/0.1 m2 in the upper and lower reaches of the Meiwan Reservoir wetlands, 0.08 snails/0.1 m2 in the Jinyan Lake of Guanghan City, 0.21 snails/0.1 m2 in Muhe River of Guanghan City, and 0.02 snails/0.1 m2 prior to the construction of Qiong-hai wetland park in Xichang City in 2015. Artificial simulation experiments showed that the largest distance of snail diffusion in water was 2 000 m. There were 8.80% (41/466) of subjects that lived neighboring wetlands, worked in wetlands and visited wet-lands having infested water contact behaviors. A total of 690 sentinel mice were assigned, and no Schistosoma japonicum infection was detected in the 677 mice dissected. Retrospective survey showed that the construction of the Meiwan Reservoir caused the spread of schistosomiasis in Dailing County, and snails were found in the ditches entering the Jinyan Lake and in Jinyan Lake areas 5 years following the construction of the Jinyan Lake in Guanghan City, with S. japonicum -infected snails detected in the ditches entering the Jinyan Lake. Conclusions O. hupensis snails are found in some wetlands in Sichuan Province. Protection of wetlands and snail control with environmental improvements are recommended for the prevention of snail importation in natural wetlands, while in artificial wetlands, thorough snail control is recommended during the construction of the wetlands because of the likelihood of snail importation via water systems. In addition, both natural and artificial wetlands require long-term systematic surveillance of schistosomiasis.
ABSTRACT
Objective To build a schistosomiasis transmission risk surveillance system in Sichuan Province, so as to provide technical support for facilitating the progress towards schistosomiasis elimination in the province. Methods The surveillance sites for schistosomiasis transmission risk were assigned in 63 endemic counties (districts) of 11 cities (prefectures) in Sichuan Province. During the period from 2015 through 2018, wild feces contamination, the sources of Schistosoma japonicum infections (fever patients, livestock and wild animals), water infectivity in key settings, snail distribution in key settings, and snail breeding risk (snail importation and spread, floating debris carrying snails and snail breeding in ecological wetlands) were monitored in the surveillance sites. Results From 2015 to 2018, a total of 1 636 wild faces were detected in Sichuan Province, and 3 faces were positive for S. japonicum, with a 0.18% positive rate; among 3 995 livestock and 59 wild mice monitored, no S. japonicum infection was detected. A total of 49 414 fever patients were monitored in 2018, and 493 were seropositive for S. japonicum infection; then, 445 seropositives were subjected to stool examinations, and no egg-positives were found. From 2010 to 2018, a total of 93 sentinel sites were assigned, and 3 994 sentinel mice were placed for monitoring the water infectivity, with one S. japonicum-infected mouse detected. Between 2015 and 2018, a total of 4 156 key settings were investigated covering an area of 1 998.46 hm2, and 668 settings were detected with snails (16.07%), covering an area of 193.26 hm2; 497 suspected settings with a likelihood of snail importation with plant introduction were monitored from 2017 to 2018, and 65 settings with snails were found with 2 673 snails captured; 593 sites were assigned to collect the floating debris from 2017 to 2018, and 9 191.39 kg floating debris were collected with 186 snails captured; 4 wetlands were monitored for the risk of schistosomiasis transmission from 2013 to 2015, and snail breeding was found in 2 wetlands. No S. japonicum infection was identified in snails captured from all surveillance sites. Conclusions A sensitive and effective schistosomiasis transmission risk surveillance system has been successfully established in Sichuan Province. There is still a risk of schistosomiasis transmission risk in local areas of Sichuan Province. Therefore, the integrated schistosomiasis control measures with emphasis on the control of the source of S. japonicum infections should be further intensified, and snail monitoring and control and monitoring and control of schistosomiasis in wetlands should be also intensified.