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Schistosomiasis was endemic to 12 provincial-level administrative divisions (PLADs) in the middle and lower reaches of the Yangtze River and southern China. Oncomelania hupensis (O. hupensis) was the only intermediate snail host of Schistosoma japonicum (1). Previous studies had illustrated that the contribution of cattle feces to the transmission of schistosomiasis had accounted for 75% (2). In order to detect these potential risks of schistosomiasis transmission, indicators including distribution and infection rates of O. hupensis and livestock’s feces around O. hupensis habitats were assessed at the beginning of transmission season in the 7 PLADs where schistosomiasis elimination had not achieved the national criteria (3). The rapid assessments were conducted in the spring of 2019 and 2021. The O. hupensis survey was performed by means of environmental sampling, and livestock feces samples were collected in surveyed O. hupensis habitats. Loop-mediated isothermal amplification (LAMP) assay and miracidial hatching were used to detect for O. hupensis infection and livestock’s feces samples, respectively. In 2021, 2 surveyed environments detected nucleic acids of schistosomes among O. hupensis snails by LAMP assay. Schistosome eggs were found in cattle feces collected from snail habitats both in 2019 and 2021. These results indicated that the distribution and infections of O. hupensis and livestock’s feces may cause concerns in endemic areas, which also gave an early warning that rapid response measures should be implemented in key environments to eliminate the potential risks of schistosomiasis transmission as soon as possible.
The assessments were conducted in the schistosomiasis endemic areas of Hunan, Hubei, Jiangxi, Anhui, Jiangsu, Sichuan, and Yunnan Provinces. Stratified random sampling was used to select surveyed environments. In each surveyed environment, over 50 square frames of 0.1 m2 were used to capture all O. hupensis within the frame. Every 10 specimens of captured O. hupensis were pooled in 1 centrifuge tube (1 tube for less than 10 O. hupensis) for DNA extraction, and DNA extracted from 50 O. hupensis samples were pooled for LAMP assay to detect S. japonicum. Surveyed environments with LAMP-tested positive O. hupensis were categorized as a positive environment. Livestock’s feces found in surveyed O. hupensis fields were all collected. Stool samples were categorized as positive if schistosome miracidia was detected by the hatching test (3 bottles for 1 sample). The proportion of frames with living O. hupensis to total surveyed frames, rate of positive O. hupensis habitats, and positive livestock-feces samples were calculated.
A total of 33 administrative villages in 14 counties of the 7 PLADs were sampled in 2019 and 2021 without duplicate sampled counties (Table 1–2). In 2019, 68 O. hupensis inhabited environments were surveyed, in which 41.18% (28/68) environments had O. hupensis captured. Out of the total of 3,115 surveyed frames, living O. hupensis occurred in 324 frames. A total of 1,919 O. hupensis were living of all 2,076 captured, and an irrigation ditch in Laoguanju Village (Hubei Province) had the highest number of living O. hupensis in single frame at 69/frame. The LAMP assay detected no positive environments from all surveyed fields. A total of 56 stool samples were found in 7 sampled counties’ surveyed environments, including 53 (94.64%) cattle-feces samples and 3 (5.36%) sheep-feces samples. A total of 4 cattle-feces sample from a marshland in Minglang Village (Hunan Province) tested positive by miracidial hatching, with a 7.14% (4/56) positivity rate of livestock-feces samples (Table 1).
Province County/City/
DistrictNumber of investigated villages Number of surveyed environments O. hupensis survey result Livestock’s feces survey result Frames with living O. hupensis/total surveyed frames LAMP result* Count Miracidial hatching positive Jiangsu Jiangning District 2 7 52/204 0 0 0 Pukou District 4 6 39/187 0 0 0 Anhui Wuwei County 2 4 3/210 0 8 0 Sanshan District 2 3 0/160 0 0 0 Jiangxi Pengze County 2 4 13/222 0 0 0 Ruichang City 3 5 30/271 0 0 0 Hubei Chibi City 3 6 30/303 0 3 0 Jiayu County 3 6 20/306 0 0 0 Hunan Ziyang District 2 4 81/205 0 18 4 Nan County 2 4 32/203 0 20 0 Sichuan Dechang County 2 5 2/205 0 0 0 Xichang City 2 6 19/239 0 3 0 Yunnan Yongsheng County 2 4 3/200 0 2 0 Jianchuan County 2 4 0/200 0 2 0 Total 33 68 324/3,115 0 56 4 Note: Based on national schistosomiasis epidemic data in the last 2 years, 2 epidemic counties (cities, districts) with relatively intense history of epidemics were selected from each province, 2 towns were selected from each sampled county (city, district), 1 village with intense history of epidemics and large extant areas of O. hupensis habitats was selected from each sampled town, and 2 possible O. hupensis inhabited environments were selected from each sampled village to conduct the field survey.
Abbreviations: PLADs=provincial-level administrative divisions; LAMP=loop-mediated isothermal amplification; O. hupensis=Oncomelania hupensis.
* LAMP results: 1: Positive, 0: Negative.Table 1. Results of rapid assessments on potential risks of schistosomiasis transmission in 7 PLADs, China, Spring 2019.
In 2021, 74 O. hupensis inhabited environments were surveyed, in which 50% (37/74) of environments had O. hupensis captured. Of the total of 3,532 surveyed frames, living O. hupensis occurred in 292 frames. In addition, of all 1,958 O. hupensis captured, 1,870 were living. In marshland and lake endemic areas, an irrigation ditch in Lianyi Village (Hubei Province) had the highest number of living O. hupensis in a single frame at 94/frame. In mountainous and hilly endemic areas, a tobacco field in Yunfeng Village (Yunnan Province) had the highest number of living O. hupensis in a single frame at 31/frame. The LAMP assay detected 2 positive environments where the nucleic acids of a schistosome were found in O. hupensis, including a marshland in Wufeng Village (Jiangxi Province) and an irrigation ditch in Lianyi Village (Hubei Province), with a 2.70% (2/74) positivity rate of O. hupensis habitats. A total of 54 stool samples were found in 13 surveyed environments in 9 sampled counties, including cattle feces, sheep feces, and other mammal’s feces, accounting for 42.59% (23/54), 38.89% (21/54), and 18.52% (10/54), respectively. One cattle-feces sample from a marshland in Lianxu Village (Jiangxi Province) tested positive by miracidial hatching, with a 1.85% (1/54) positivity rate of livestock-feces samples (Table 2).
Province County/City/
DistrictNumber of investigated villages Number of surveyed environments O. hupensis survey result Livestock’s feces survey result Frames with living O. hupensis/total surveyed frames LAMP result* Count Miracidial hatching positive Jiangsu New Zhenjiang District 2 4 2/213 0 1 0 Yangzhong City 2 4 3/208 0 3 0 Anhui Wanzhi Distrcit 2 6 31/223 0 21 0 Xuanzhou District 2 9 14/219 0 0 0 Jiangxi Jinxian County 2 3 0/162 0 4 0 Nanchang County 3 5 11/293 1 13 1 Hubei Shashi District 3 8 1/439 0 1 0 Jingzhou District 3 6 42/187 1 2 0 Hunan Hanshou District 2 4 8/209 0 0 0 Dincheng District 3 4 18/209 0 6 0 Sichuan Mianzhu City 2 4 88/240 0 0 0 Jingyang District 2 4 63/233 0 0 0 Yunnan Heqing County 3 8 0/435 0 3 0 Dali City 2 5 11/262 0 0 0 Total 33 74 292/3,532 2 54 1 Note: Based on national schistosomiasis epidemic data in the last 2 years, 2 epidemic counties (cities, districts) with relatively intense history of epidemics were selected from each province, 2 towns were selected from each sampled county (city, district), 1 village with intense history of epidemics and large extant areas of O. hupensis habitats was selected from each sampled town, and 2 possible O. hupensis inhabited environments were selected from each sampled village to conduct the field survey.
* LAMP results: 1: Positive, 0: Negative.
Abbreviations: PLADs=provincial-level administrative divisions; LAMP=loop-mediated isothermal amplification; O. hupensis=Oncomelania hupensis.Table 2. Results of rapid assessments on potential risks of schistosomiasis transmission in 7 PLADs, China, Spring 2021.
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