Endemic situation of schistosomiasis in national surveillance sites of Anhui Province from 2020 to 2024

doi:10.12140/j.issn.1000-7423.2025.04.006

Abstract

Abstract:

Objective To investigate the changes in the endemic situation of schistosomiasis in national surveillance sites of Anhui Province, so as to provide the scientific evidence for promoting the schistosomiasis elimination strategy in the provinc. Methods According to the requirements of the National Schistosomiasis Surveillance Scheme in China (2020 Edition), national schistosomiasis surveillance were assigned in 50 endemic counties (cities, districts) across Anhui Province. During the period between October and November from 2020 to 2024, schistosomiasis surveillance was performed among permanent residents at ages of over 6 years in surveillance villages from class I surveillance counties, with no less than 300 residents in each village, and schistosomiasis screening was conducted among mobile populations by means of active surveillance and sentinel hospitals-based passive surveillance, with no less than 200 populations in each county. Serological screening of schistosomiasis was performed using indirect hemagglutination test, and sero-positive individuals were subjected to parasitological examinations using egg hatching tests with nylon gauzes (three slides for one sample) and modified Kato-Katz thick smear technique (three slides for one sample). During the period between October and December from 2020 to 2024, Schistosoma japonicum infection was detected in livestock using the miracidium hatching test. Oncomelania hupensis snail distribution was surveyed using systematic sampling combined with environmental sampling in each spring from 2020 to 2024, and S. japonicum infection was detected in O. hupensis snails using microscopy. S. japonicum nucleic acid was detected in O. hupensis snails using loop-mediated isothermal amplification (LAMP) assay in class Ⅰ and Ⅱ surveillance counties where the transmission of schistosomiasis was achieved during the recent 5 years, and the surveillance of wild feces and snail distribution was performed in snail-infested habitats in some administrative villages in class Ⅰ surveillance counties and some class Ⅱ surveillance counties in each spring from 2020 to 2024. Results Serological screening for schistosomiasis was conducted among local residents at 63 868 person-times in Anhui Province from 2020 to 2024, and there were 908 sero-positives detected (530 males and 378 females). The seroprevalence of schistosomiasis reduced from 1.49% (263/17 644) in 2020 to 1.23% (118/9 592) among local residents in 2024. Serological screening for schistosomiasis was conducted among mobile populations at 55 587 person-times in Anhui Province from 2020 to 2024, with 104 sero-positive cases detected (71 males and 33 females), with a reduction from 0.41% (43/10 596) in 2020 to 0.07% (8/10 889) in 2024. Nevertheless, no egg-positives were identified among local residents or mobile populations. A total of 5 812 livestock were tested for S. japonicum infections, with no infections identified. A total of 7 810 settings were surveyed for snail distribution from 2020 to 2024, covering an area of 593.85 km², and the area with snail habitats reduced from 37.80 km² in 2020 to 34.90 km² in 2024. A total of 1 101 819 frames were surveyed for snails using a systematic sampling method, and the 5-year mean occurrence of frames with snails and density of living snails were 8.51% and 0.30 snails per 0.11 m², respectively. The highest occurrence of frames with snails was seen in ditches (12.16%, 8 174/672 091), dry lands (6.57%, 489/2 952), ditches (13.55%, 7 455/55 019), ditches (10.13%, 5 198/51 316), and ditches (10.19%, 6 669/65 441) from 2020 to 2024, respectively, and there were significant differences in the occurrence of frames with snails in different types of endemic areas from 2020 to 2024 (χ² = 2 012.52, 3 174.12, 5 501.59, 1 454.46, 720.04; all P < 0.01). The occurrence rates of frames with snails were higher in the hilly endemic areas (11.32%, 10.55%, 10.19%, 10.68%, and 9.48%) than in marshland and lake endemic areas (7.72%, 9.60%, 7.91%, 7.17%, and 7.63%) from 2020 to 2024 (χ² = 740.27, 35.61, 216.66, 433.64, 151.03; all P < 0.01). No S. japonicum infections were identified in snails during the intermediate host monitoring or risk monitoring, and S. japonicum infection was detected in only one wild bovine stool sample in 2022, with no S. japonicum infections identified in other wild stool samples. Conclusion The prevalence of schistosomiasis appeared an overall tendency towards a decline in Anhui Province from 2020 to 2024; however, there was still a risk of schistosomiasis transmission. Improved and intensified construction of the schistosomiasis surveillance system is recommended to provide insights into implementation of the precise schistosomiasis control strategy.

Key words: Schistosomiasis, Endemic situation, Surveillance, Anhui Province

CLC Number:

R532.21

XU Xiaojuan, DING Songjun, DAI Bo, LIU Ting, GAO Fenghua, ZHANG Shiqing. Endemic situation of schistosomiasis in national surveillance sites of Anhui Province from 2020 to 2024[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2025, 43(4): 482-488.

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References 19

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年份 Year	男性 Male			女性 Female			合计 Total
年份 Year	检查人数 No. examined	阳性人数 No. positive	阳性率/% Positive rate/%	检查人数 No. examined	阳性人数 No. positive	阳性率/% Positive rate/%	检查人数 No. examined	阳性人数 No. positive	阳性率/% Positive rate/%
2020	6 940	33	0.48	3 656	10	0.27	10 596	43	0.41
2021	6 848	13	0.19	4 223	7	0.17	11 071	20	0.18
2022	7 826	15	0.19	4 166	5	0.12	11 992	20	0.17
2023	6 940	7	0.10	4 099	6	0.15	11 039	13	0.12
2024	6 677	3	0.04	4 212	5	0.12	10 889	8	0.07

年份 Year	男性 Male			女性 Female			合计 Total
年份 Year	检查数 No. examined	阳性数 No. positive	阳性率/% Positive rate/%	检查数 No. examined	阳性数 No. positive	阳性率/% Positive rate/%	检查数 No. examined	阳性数 No. positive	阳性率/% Positive rate/%
2020	8 708	146	1.68	8 936	117	1.31	17 644	263	1.49
2021	6 148	142	2.31	6 636	78	1.18	12 784	220	1.72
2022	6 117	121	1.98	6 355	88	1.38	12 472	209	1.68
2023	5 436	56	1.03	5 940	42	0.71	11 376	98	0.86
2024	4 719	65	1.38	4 873	53	1.09	9 592	118	1.23