Spatial distribution of Clonorchiasis in Heilongjiang, 2016 - 2021

  Objective  To understand the population and spatial distributions of Clonorchis sinensis infection in Heilongjiang province from 2016 to 2021, and provide scientific evidence for the prevention and control of Clonorchiasis.

  Methods  The surveillance data of Clonorchiasis in Heilongjiang from 2016 to 2021 were collected for a descriptive analysis on the distribution of the population infected with Clonorchis sinensis. Spatial autocorrelation analysis and nuclear density estimation were used to explore the spatial distribution of Clonorchis sinensis infection in the study area.

  Results  The surveillance for Clonorchiasis covered 71 counties (districts) and 417 villages (communities) in Heilongjiang from 2016 to 2021. The overall infection rate of Clonorchis sinensis was 3.91% (4 488/114 905). The infection cases were mainly men (64.46%, 2 893/4 488), people aged 40−59 years (58.53%, 2 627/4 488), people with junior high school education (52.01%, 2 334/4 488), people in Han ethnic group (95.45%, 4 284/4 488) and farmers (herdsmen, fishers) (92.96%, 4 172/4 488). The infection rate in men (4.92%, 2 893/58 764) was higher than that in women (2.84%, 1 595/56 141). The infection rates were 5.71% in age group 40−49 years (1 358/23 785) and 5.32% in age group 50−59 years (1 269/23 867). The infection rates in junior high school and senior high school students were 4.00% (1 553/38 812) and 4.52% (2 334/51 582), respectively. The infection rate in farmers (herdsmen and fishers) was 5.11% (4 172/81 614). The infection rates in Chinese Korean and Mongolian populations were 12.85% (163/1 268) and 9.26% (34/367), respectively. There were significant differences in infection rate of Clonorchis sinensis among different sex, age, education level, population and ethnic groups (χ²=331.598, χ²=855.526, χ²=281.391, χ²=1522.040, χ²=337.219, all P<0.05). The global spatial autocorrelation analysis on the infection rate of Clonorchis sinensis in population showed that there was clustering at county level in the study area (Moran's I =0.414, Z=5.115, P=0.001). Local spatial autocorrelation analysis showed that the high-high clustering areas were mainly distributed in the northeast of the province. The global spatial autocorrelation analysis showed that there were clustering of Clonorchis sinensis infection at village (community) level in the study area (Moran's I=0.437, Z=15.897, P=0.001). Local spatial autocorrelation analysis showed that 43 villages (communities) with high-high clustering were mainly distributed in the northeast and southwest of the province, while 1 village (community) with high-low clustering was distributed in the northeast of the province. The estimation of kernel density shows that the high value area of kernel density was distributed longitudinally in the northeast and southwest of the province, mainly along the Songhua River basin.

  Conclusion  The distribution of Clonorchiasis infection in Heilongjiang showed obvious spatial clustering and distinct population distribution characteristics. It is necessary to develop targeted prevention and control strategies based on the population and spatial distributions of Clonorchis sinensis infection.