Risk assessment of schistosomiasis transmission along the middle and lower reaches of Yangtze River after flooding in 2020

doi:10.12140/j.issn.1000-7423.2021.06.005

Abstract

Abstract:

Objective This study aimed to assess the transmission risk of schistosomiasis along the middle and lower reaches of Yangtze River after flooding in 2020. Methods Snail survey and survey for contamination with wild feces in snail breeding environment were conducted in Hunan, Hubei, Jiangxi, Anhui, and Jiangsu Provinces in October, 2020. According to the historical epidemic of schistosomiasis and the flooding record, two counties of each province were selected for this study, including Nanxian, Huarong, Hanchuan, Yangxin, Lushan, Lianxi, Guichi, Zongyang, Luhe, and Hanjiang. Two townships (town) were selected from each county, and then one administrative village was selected from each township (town) for the survey. Using systematic sampling and environmental sampling method, snail survey was performed in two categories of environment in the current flood-affected area, including snail-infested environment bearing frequent human and animal activities in 2017—2019, and in environment of historically snail-free or snail-free over 20 years. All the collected snails were examined for schistosome infection by loop-mediated isothermal amplification (LAMP) method. During collecting snails from environments, wild feces were collected as well and tested by miracidia hatching method (one sample, triple detection). Chi-square test is used to compare the difference of occurrence rate of frames with living snails surveyed using systematic and environmental sampling methods. Results A total of 64 snail breeding environment sites were surveyed, from where 8 904 snails were collected, of them 7 918 were alive. The overall occurrence rate of living snail frames was 11.7% (1 813/15 464), and the rates were 10.5% (679/6 441) using environmental sampling method and 12.6% (1 134/9 023) using systematic sampling method. The difference between the two rates was statistically significantly (χ² = 14.91, P < 0.01). The occurrence rates of living snail frames by systematic sampling in Zongyang and Guichi of Anhui Province were 60.2% (607/1 008) and 28.4% (251/882), respectively, which were both significantly higher than the rates in other counties (P < 0.01). The average density of live snails in Zongyang (2.177/0.1 m²) and Guichi (3.323/0.1 m²) were over ten folds higher than those in other counties. One sample collected from in Guichi was found schistosome positive detected by LAMP method. A total of 100 wild feces samples were collected from 47 snail breeding environment, three of them were found schistosome positive, which belong to cattle, located in two environments in Lushan, Jiangxi and one environment in Guichi, Anhui. A total of 572 snails were collected from 44 sites of historically snail-free environment and the environment of snail-free for over 20 years, and 550 living snails were detected. These snails were found in the potential spreading areas in one environment in Guichi, Anhui, and two environments in Lushan, Jiangxi, with the average occurrence rates of living snail frames by systematic sampling being 21.2% and 4.5% respectively, showing the average densities of living snails being 1.254/0.1 m² and 0.081/0.1 m² respectively. Two samples collected from Lushan, Jiangxi were detected as schistosome positive by LAMP. Conclusion The flooding in 2020 may expand the schistosomiasis transmission areas in middle and lower reaches of Yangtze River, among them the transmission risk in Anhui and Jiangxi Provinces rose, compared to the previous year.

Key words: Schistosomiasis, Flooding, Transmission risk, Yangtze River, Snail survey

CLC Number:

R532.2

GUO Su-ying, ZHU Hong-qing, CAO Chun-li, DENG Wang-ping, BAO Zi-ping, JIA Tie-wu, LI Yin-long, LV Chao, QIN Zhi-qiang, ZHANG Li-juan, FENG Ting, YANG Fan, LV Shan, XU Jing, LI Shi-zhu. Risk assessment of schistosomiasis transmission along the middle and lower reaches of Yangtze River after flooding in 2020[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2021, 39(6): 753-758.

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调查地区Survey area	环境抽查Environmental sample					系统抽样Systematic sample
调查地区Survey area	调查框数 /框 No. frame	活螺框数 /框 No. frame with living snails	活螺框出现率/% Occurrence rate of live snails/%	采集总螺数/只 No. snail	活螺数/只 No. living snail	调查框数 /框 No. frame	活螺框数 /框 No. frame with living snails	活螺框出现率/% Occurrence rate of live snails/%	采集总螺数/只 No. snail	活螺数/只 No. living snail	活螺平均密度 /只·0.1m^2-1 Density of living snail /No.·0.1m^2-1
湖北省Hubei 阳新县 Yangxin	2 789	119	4.3	641	623	0	0	0	0	0	0
汉川市 Hanchuan	1 024	0	0	0	0	1 234	64	5.2	488	300	0.243
湖南省Hunan 南县Nanxian	275	18	6.5	34	32	776	65	8.4	136	113	0.146
华容县 Huarong	230	70	30.4	170	90	780	41	5.3	67	50	0.064
江西省 Jiangxi 濂溪区 Lianxi	257	32	12.5	71	66	2 483	102	4.1	234	216	0.087
安徽省 Anhui 枞阳县 Zongyang	185	105	56.8	373	338	1 008	607	60.2	2 632	2 194	2.177
贵池区 Guichi	445	61	13.7	621	596	882	251	28.5	3 059	2 931	3.323
江苏省 Jiangsu 六合区 Luhe	1 054	208	19.7	258	256	0	0	0	0	0	0
邗江区 Hanjiang	182	66	36.3	111	105	1 860	4	0.2	9	8	0.004
合计Total	6 441	679	10.5	2 279	2 106	9 023	1 134	12.6	6 625	5 812	0.644

调查地区Survey area	环境抽查Environmental sample					系统抽样Systematic sample
调查地区Survey area	调查框数 /框 No. frame	活螺框数 /框 No. frames with living snail	活螺框出现率/% Occurrence rate of live snail/%	采集总螺数/只 No. snail	活螺数/只 No. living snail	调查框数/框 No. frame	活螺框数/框 No. frames with living snail	活螺框出现率/% Occurrence rate of live snail/%	采集总螺数/只 No. snail	活螺数/只 No. living snail	活螺平均密度/只·0.1m^2-1 Density of living snail
湖北省Hubei 阳新县 Yangxin	1 490	0	0	0	0	0	0	0	0	0	0
汉川市 Hanchuan	420	0	0	0	0	0	0	0	0	0	0
湖南省 Hunan 南县 Nanxian	1 280	0	0	0	0	0	0	0	0	0	0
华容县 Huarong	430	0	0	0	0	0	0	0	0	0	0
江西省 Jiangxi 濂溪区 Lianxi	1 255	0	0	0	0	0	0	0	0	0	0
庐山市 Lushan	543	85	15.7	358	358	529	24	4.5	54	43	0.081
安徽省 Anhui 枞阳县 Zongyang	1 144	0	0	0	0	0	0	0	0	0	0
贵池区 Guichi	110	1	0.9	1	1	118	25	21.2	159	148	1.254
江苏省 Jiangsu 六合区 Luhe	438	0	0	0	0	0	0	0	0	0	0
邗江区 Hanjiang	703	0	0	0	0	0	0	0	0	0	0
合计Total	7 813	86	1.1	359	359	647	49	7.6	213	191	0.295

调查地点 Survey area	调查环境数 No. environment	野粪数 No. wild fece	阳性野粪数 No. positive wild fece
湖北省Hubei 阳新县 Yangxin	10	0	0
汉川市 Hanchuan	3	0	0
湖南省Hunan 南县 Nanxian	2	6	0
华容县 Huarong	6	0	0
江西省Jiangxi 濂溪区 Lianxi	4	21	0
庐山市 Lushan	8	50	2
安徽省Anhui 枞阳县 Zongyang	9	4	0
贵池区 Guichi	3	8	1
江苏省Jiangsu 六合区 Luhe	1	10	0
邗江区 Hanjiang	1	1	0
合计Total	47	100	3