Analysis of transmission risk factors of schistosomiasis in a hilly demonstration plot of transmission interruption

Abstract

Abstract:

Objective To analyze the risk factors for schistosomiasis transmission in a hilly transmission interruption demonstration plot located at the south bank of Yangtze River. Methods The 2016-2017 schistosomiasis endemic information in local residents and livestock in a hilly transmission interruption demonstration plot located at the south bank of Yangtze River was collected. Field investigations were also carried out at benchland, cement ditch, field drain, flood discharge ditch, trunk canal, wasteland, desolate sands in the demonstration plot, where snails were surveyed through systematic sampling in combination with environmental sampling, and wild rodents were captured using cages or traps which were placed monthly, 3 days each time, for 3 consecutive months. The loop-mediated isothermal amplification (LAMP) method was used to detect the schistosome DNA in snails. The rodents captured were sacrificed and liver tissues were collected for egg examination in tissue homogenates. Feces from wild animals in the field were collected, and examined by the miracidium hatching method. Results A total of 12 232 (5 408/6 824) local residents were examined in 2016 and 2017 in the demonstration plot, of whom 152 showed positive serological test results and none showed positive fecal examination result. A total of 688 cattle were examined by serological test, of which only 1 showed positive result, and none showed positive fecal examination result. Meanwhile, 2 152 frames of snails were investigated in the 7 selected areas and 1 401 snails were obtained, including 1 398 live snails (427 frames), with an average density of 3.27 live snails/frame. The LAMP results showed that 5 out of 24 tubes of mixed DNA resulted in positive products, distributed at 3 sites. A total of 825 cages/traps were placed, and only 35 rodents were captured, distributed at 6 sites. None of the rodents were found to be infected with Schistosoma japonicun after stool hatching, while microscopic examination of the liver tissue revealed two rodents infected with Clonorchis sinensis. The purchased 2 samples of wild boar liver and one wild rabbit also showed negative results of microscopic examination and fecal hatching. A total of 137 fecal samples were collected, mainly from two spots (54 and 44 from each). The fecal samples were from cattle, goats, horses, swines and dogs, mostly from cattle (66 samples), and least from swines (4). Twenty-six were determined as positive by hatching, infection a positive rate of 19.0%, consisting of 15 cattle feces, 2 horse feces, 3 goat feces, 3 swine feces, and 3 dog feces. Conclusion No human cases of schistosomiasis were found in the demonstration plot. There has been a scenario of multiple livestock sources of infection in the demonstration plot, with an infection rate of 19.0% in livestock feces. The infected livestock feces are a crucial factor for the transmission of schistosomiasis in this area.

Key words: Schistosomiasis, Wildlife, Snail, Investigation of field feces

CLC Number:

R532.21

Chao LV, Li-yuan ZHOU, Xiao-ying XING, Dan-dan LIN, Tao CHEN, Rui CHEN, Han-chen KE, Zhou WANG, Wu PAN, Jing XU, Zhi-qiang QIN, Hong-qing ZHU, Shi-zhu LI. Analysis of transmission risk factors of schistosomiasis in a hilly demonstration plot of transmission interruption[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2018, 36(4): 333-339.

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References 28

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年份 Years	人血吸虫病疫情 Human schistosomiasis					家畜血吸虫病疫情Domestic animal schistosomiasis
年份 Years	检查人数 No. exam’d	血检人数 No. serological test	血检阳性人数No. patients with positive serological results	粪检人数 No. stool exam’d	粪检阳性人数 No. patients with positive stool examination	存栏数 No. on hand	血检头数 No. serological tests	血检阳性头数 No. livestock with positive serological results	粪检头数 No. stool exam’d	粪检阳性头数 No. livestock with positive stool examination
2016	5 408	5 308	63	158	0	329	330	1	1	0
2017	6 824	6 824	89	289	0	329	358	0	50	0
合计Total	12 232	12 132	152	447	0	658	688	1	51	0

调查点 Spots	调查面积/m² Area of investigation/m²	调查框数 No. frames	活螺框数 No. frames with living snails	检获钉螺数 No. snails	活螺数 No. living snails	单框最高钉螺数 Maximum number of snails per frame	核酸检测管数 No. test tubes for DNA	阳性管数 No. positive	阳性比例/% Percentage/%
乌石河滩Benchland	4 500	305	45	145	145	19	2	0	0
水泥沟Cement ditch	1 500	310	78	294	294	34	5	2	40
田间沟Field drain	1 750	312	83	289	289	29	5	1	20
泄洪沟 Flood discharge ditch	1 700	315	47	167	167	17	3	0	0
干渠Trunk canal	2 400	300	70	234	234	39	4	2	50
荒地Wasteland	2 300	309	61	178	178	12	3	0	0
荒滩Desolate sands	2 000	301	43	94	91	9	2	0	0
总计 Total	16 150	2 152	427	1 401	1 398		24	5	20.8

调查点 Spot	捕捉面积/m² Capture areas/m²	共投放鼠笼（夹） No. cages (traps)	回收数 No. recovered	捕获鼠数 No. captured	鼠密度/只·m^-2 Rodent density/m²	解剖肝脏钙化数 No. liver calcification	镜检寄生虫种类 Parasite species examined by microscope
乌石河滩Benchland	3 000	120	117	0	0	0
水泥沟Cement ditch	1 500	105	96	7	0.073	0
田间沟Field drain	1 750	120	117	3	0.026	0
泄洪沟Flood discharge ditch	1 500	120	115	6	0.052	1	华支睾吸虫Clonorchis sinensis
干渠Trunk canal	2 400	135	129	10	0.078	1	华支睾吸虫Clonorchis sinensis
荒地Wasteland	2 300	120	118	4	0.034	0
荒滩Desolate sands	2 000	105	104	5	0.048	0
总计Total	14 450	825	796	35	0.044	0

调查点 Spots	调查面积/m² Area of investigation/m²	野粪种类 Wild fecal species	野粪数 No. wild feces	野粪密度/份·m^-2 Density/m²	孵化毛蚴阳性数 No. miracidium positive	阳性比例/% Percentage/%
乌石河滩Benchland	4 500	牛粪Cattle	5	0.002 7	1	25.0
		羊粪Goat	2		0
		马粪Horse	5		2
水泥沟Cement ditch	2 500	犬粪Canine	1	0.000 8	0	0.0
水泥沟Cement ditch		猪粪Swine	1		0
田间沟Field drain	3 000	牛粪Cattle	44	0.014 7	5	11.4
泄洪沟Flood discharge ditch	2 500	犬粪Canine	7	0.004 0	3	6/10
泄洪沟Flood discharge ditch		猪粪Swine	3		3
干渠Trunk canal	3 000	牛粪Cattle	13	0.004 3	8	8/13
荒地Wasteland	2 300	羊粪Goat	2	0.000 9	2	2/2
荒滩Desolate sands	2 000	羊粪Goat	33	0.027 0	1	3.7
		马粪Horse	17		0
		牛粪Cattle	4		1
总计 Total	19 800		137	0.006 9	26	19.0