关键词: 华支睾吸虫, 中间宿主, 保虫宿主, 感染率, 监测

Abstract:

Objective To ascertain the endemic status of Clonorchis sinensis in Zhejiang Province. Methods From 2013 to 2017, one county (city, district) which had clonorchiasis cases reported before in Zhejiang Province was selected as the regular surveillance site and 3 townships in each site were selected for monitoring each year. No less than 100 permanent residents over age 3 in each township were selected as monitored objects. Venous blood samples were collected, and serum C. sinensis antibody was detected by enzyme-linked immunosorbent assay (ELISA). The positive rate of antibodies in the monitored objects was calculated. And questionnaire surveys were conducted on the factors affecting the infection of C. sinensis from 2013 to 2015. From 2018 to 2022, Ningbo City was selected as the fixed surveillance site and 7-9 counties (cities, districts) were selected as the mobile surveillance sites. Each surveillance site was divided into 5 areas as geographically at east, west, south, north and centre. In each area, one administrative village was randomly selected from one township for cluster sampling of no less than 200 permanent residents over age 3. Fecal samples (over 30 g) were collected for examining C. sinensis eggs using the modified Kato-Katz thick smear method. The infection rate of the monitored object was calculated. Freshwater fish from natural water were collected in regular surveillance sites from 2013 to 2017 and in the fixed surveillance site and a mobile surveillance site from 2018 to 2022. The infection of encysted metacercaria was detected by pressing method after identified the species. From 2018 to 2022, the fecal samples of cats, dogs and pigs were collected in surveillance sites which monitoring the intermediate hosts, and examined C. sinensis eggs using the modified Kato-Katz thick smear method. SPSS 19.0 was used for data statistical analysis. Infection rates were compared between groups using the chi-squared test. Results From 2013 to 2017, a total of 1 516 people were examined in Zhejiang Province and antibody positive rate was 2.51% (38/1 516). A total of 52 626 people were examined from 2018 to 2022. No C. sinensis eggs were found in fecal samples and the infection rate was 0 (0/52 626). The highest antibody positive rate of 6.00% (18/300) was seen in Panan County. The antibody positive rate in different surveillance sites was statistically significant (χ² = 21.212, P < 0.01). The highest antibody positive rate of 8.82% (6/68) was seen in the age 3-17 group. The antibody positive rate in different age groups was statistically significant (χ² = 13.105, P < 0.05). The infection rate of C. sinensis in freshwater fish from 2013 to 2022 were 12.56% (476/3 791). The highest infection rate of 33.47% (84/251) was seen in Ninghai County in 2018. The infection rate in different surveillance sites was statistically significant (χ² = 242.727, P < 0.01). The highest infection rate of 75.00% (21/28) was seen in Acanthobrama simoni. The infection rate in different fish species was statistically significant (χ² = 174.750, P < 0.01). The infection rate of reservoir host was 1.17% (3/257). Conclusion The infection rate of C. sinensis in human population was considerably low in surveillance sites in Zhejiang Province, but the infected intermediate hosts and reservoir hosts still remained, which poses a potential epidemic risk and requires strengthened surveillance, prevention and health education.

Key words: Clonorchis sinensis, Intermediate host, Reservoir host, Infection rate, Surveillance