Abstract:

Objective To understand the current status of soil-transmitted nematode infections in Jiangsu Province from 2017 to 2021, and provide the basis for the formulating scientific prevention and control strategies. Methods From 2017 to 2021, eight counties (cities, districts) in Jiangsu Province were selected as surveillance sites each year (one fixed site, and seven ambulatory sites changed on yearly base). The surveillance sites were randomly selected from five geographical sections in the east, west, south, north and centre, from each of which one township (town) was selected to set up surveillance site therein one administrative village. No less than 200 permanent residents over the age of 3 in each administrative village were selected for surveillance. About 30 g of fecal sample was collected from each participant for examining nematode eggs using the modified Kato-Katz thick smear method (two slide-reading each sample), to calculate infection rate and intensity of different species.. Hookworm-positive fecal samples were used to identify parasite species by test tube-filter paper culture method. Children aged 3 to 9 years old were additionally examined for Enterobius vermicularis infection by adhesive cellophane swabs method. Five households were randomly selected from each village at fixed surveillance site to collect soil sample (≥ 400 g) from vegetable garden or field of each household, of which 350 g were used for detection of hookworm eggs, and 50 g for Ascaris lumbricoides eggs. Infection rates were compared between groups using the chi-square test. Results From 2017 to 2021, a total of 41 753 people were examined in Jiangsu Province surveillance sites, and found the overall infection rate of soil-transmitted nematodes at 0.30% (124/41 753). The infection rates of A. lumbricoides, hookworm, Trichuris trichura and Enterubius vermicularis were 0.13% (56/41 753), 0.06% (24/41 753), 0.02% (10/41 753) and 0.08% (34/41 753) respectively, and all soil-transmitted nematode infections were of mild type. The infection rate of soil-transmitted nematodes at fixed monitoring site was 0.37% (21/5 699), while that at mobile monitoring sites were 0.29% (103/36 054). There was no significant difference between different sites (χ² = 0.19, P > 0.05)。From 2017 to 2021, the five-year infection rates of soil-transmitted nematodes were 0.26% (22/8 549), 0.54% (46/8 452), 0.22% (19/8 454), 0.37% (30/8 189) and 0.09% (7/8 109), respectively, with statistically significant differences in infection rates between years (χ² = 32.88, P < 0.01). The highest infection rate of soil-transmitted nematodes was seen in Lianyungang (1.17%, 48/4 119), followed by Suqian (0.38%, 21/5 487) and Huai’an (0.36%, 11/304), with statistically significant differences among the different cities (χ² = 137.52, P < 0.01). The infection rate was 0.26% (52/19 773) in males and 0.33% (72/21 980) in females (χ² = 1.47, P > 0.05). For differences in age groups, the highest infection rate was found in the 3-9 years age group (0.86%, 35/4 093), with statistically significant differences among the different age groups (χ² = 53.24, P < 0.01). For differences in occupations, the highest infection rate was found among children in kindergarten (1.21%, 22/1 811), with statistically significant differences among different occupational groups (χ² = 45.56, P < 0.01). For education levels, the highest infection rate was found among preschool children (1.24%, 25/2 020), with statistically significant differences among people with different levels of education (χ² = 54.96, P < 0.01). A total of 125 soil samples from fields or vegetable gardens were tested from 2017 to 2021, and one hook larva was detected (identified as duodenal hook larva by microscopic examination), with a positive rate of 0.8% for hookworm larva in soil samples, and no eggs of A. lumbricoides were detected. Conclusion The prevalence of soil-transmitted nematode infection in Jiangsu Province has been at a very low level since 2017. In the future, more attention should be paid to the key groups of children and the elderly in the northern part of Jiangsu Provinces.

Key words: Soil-transmitted nematode, Infection, National surveillance sites, Jiangsu Province