Abstract:

Objective To analyze the seroepidemiological characteristics in transient population and the moving direction of the individuals with positive serum anti-schistosome antibody at national schistosomiasis surveillance sites of China during 2020-2022, and to provide a scientific basis for formulating surveillance program for schistosomiasis in the transient population. Methods Data of the national population-based schistosomiasis surveillance and individual cases recorded from transient population during 2020-2022 were collected from the Information System for Infectious Diseases Prevention and Control and the Information System for Parasitic Disease Prevention and Control. The data include demographic characteristics of sex, age, occupation and the counties of residence registered, and the people migrating information regarding the locations of moving in or moving out from, as well as the results of serological and pathogenic examinations for schistosomiasis. Descriptive epidemiological methods were employed to analyze the spatial, temporal, and demographic distribution of the serum anti-schistosome level among the transient population. Chi-square analysis was used to compare the differences in the positive rates of serum antibodies among the groups of sex, age, and occupation. Partitions of χ² method was used for multiple comparisons of the positive rates. Sankey diagram was used to describe the moving direction of the individuals with positives serum antibodies. Results A total of 302 460 person-time among the transient population was surveyed from 455 surveillance counties in 13 provinces (or autonomous regions or municipalities) in China from 2020 to 2022, and 1 199 was found positive with serum antibodies, and one was positive with fecal examination. During 2020-2022, the positive rates of serum antibodies among the transient population were 0.47% (450/96 596), 0.44% (442/101 558), and 0.29% (307/104 306), respectively. The rates in 2020 and 2021 were both higher than the rate in 2022 (χ² = 39.310, 28.178; both P < 0.01). During 2020-2022, the highest positive rates of serum antibodies were detected in Jiangxi, showing 1.24% (91/7 316), 1.33% (112/8 412), and 0.65% (56/8 648), respectively. The positive rates of serum antibodies were 0.48% (277/57 550), 0.44% (260/59 458), and 0.31% (191/62 237) in males and 0.44% (173/39 046), 0.43% (182/42 100), and 0.28% (116/42 069) in females, respectively. No statistically significant differences were observed between sex groups in each year (χ² = 0.734, 0.014, 0.830; all P > 0.05). The positive rates of serum antibodies were 0.82% (225/27 561), 0.78% (226/28 928) and 0.53% (158/29 661) in farmers, 0.86% (20/2 333), 0.75% (16/2 141) and 0.91% (23/2 523) in boatmen/fishermen, and 0.31% (205/66 702), 0.28% (200/70 489) and 0.17% (126/72 122) in other occupation group, respectively. The positive rates of serum antibodies were higher in the farmers and boatmen/fishermen groups compared to the other occupation group (χ² = 111.287, 118.991, 96.799; 20.985, 15.060, 66.450; all P < 0.01). The positive rates of serum antibodies in group of 6-15 years were the highest (1.00%, 16/1 597) in 2020, the second highest (0.70%, 10/1 436) in 2021, and the lowest (0.05%, 1/1 836) in 2022, respectively. The differences among different age groups were statistically significant for each year (χ² = 41.282, 56.515, 54.425; all P < 0.01). Among the seropositive individuals who provided complete information on their migration regions, higher proportions of emigration location were seen from Sichuan (21.86%, 256/1 171), Jiangxi (21.18%, 248/1 171), and Hubei (18.02%，211/1 171), and the highest two destinations were Jiangxi (18.87%, 221/1 171) and Sichuan (18.87%, 221/1 171). Among the seropositive individuals who provided complete migration information, higher proportions of emigration location were seen from Sichuan (21.86%, 256/1 171), Jiangxi (21.18%, 248/1 171), and Hubei (18.02%, 211/1 171). The higher proportions of immigration location were seen in Jiangxi (18.87%, 221/1 171) and Sichuan (18.87%, 221/1 171); the proportion of immigration location within or between non-eliminated provinces was 73.87% (865/1 171), and the proportion of migrants moving between non-eliminated and eliminated provinces was 19.98% (234/1 171). Forty-six individuals with positive serum antibodies migrated from non-endemic areas to endemic areas. Conclusion According to the survey of the national surveillance sites, the prevalence of schistosomiasis in transient population in China remained at a very low level from 2020 to 2022. It is imperative to strengthen the surveillance for the transient population in Jiangxi, younger age group and the migrants moving in or out from non-elimination areas, as well as the proper management of people with past infections.

Key words: Schistosomiasis, Surveillance, Transient population, Moving direction