Abstract:

To analyze the prevalence and epidemic trend of soil-transmitted nematode infection at a national surveillance site of Xiangcheng District in Zhangzhou City from 2016 to 2020. Tianbao Village and Dazhai Village in Tianbao Town, Punan Village and Pulin Village in Punan Town, and Gaokeng Village in Shiting Town were selected as the survey sites in Xiangcheng District. No less than 200 permanent residents aged 3-years or above were selected from each administrative village. Fecal samples were collected from the residents recruited in the study and were examined for soil-transmitted nematode eggs (two slide-reading per sample) using the modified Kato-Katz thick smear method. The cellophane tape method was used to detect the eggs of Enterobius vermicularis in children aged 3-9 years. For individuals with hookworm infection, the test-tube filter paper incubation method was used to culture hookworms and identify the species of hookworms. Five households were randomly selected from each village, and one soil sample from the field or vegetable garden was collected for each household to check for Ascaris eggs and hookworms. From 2016 to 2020, a total of 5 309 local residents were tested, and the total infection rate was 3.0% (159/5 309). The infection rates of hookworm and Trichuris trichiura were 2.9% (154/5 309) and 0.1% (5/5 309), respectively. No A. lumbricoides infection was found. Six hundred twenty-five children aged 3-9 were examined, and the E. vermicularis infection rate was 27.8% (174/625). The infection rates for males and females were 3.7% (96/2 608) and 2.3% (63/2 701), respectively. The difference was statistically significant (χ² = 8.31, P < 0.01). The highest infection rate was 7.3% (79/1 077) in ≥ 65 years age group with a statistically significant difference between the age groups (χ² = 123.51, P < 0.01). The infection rate was higher among farmers, with 3.6% (157/4 325) than in other occupations. The difference was statistically significant (χ² = 32.95, P < 0.01). The highest infection rate was in illiterate and semi-literate residents 10.1% (79/781) with statistically significant difference between the educational levels (χ² = 171.18, P < 0.01). The total infection rates of soil-derived nematodes between 2016 and 2020 were 3.9% （44/1 126）, 1.0% （11/1 104）, 7.6% （78/1 029）, 0.9% （9/1 013） and 1.6% （17/1 037）, respectively. The infection rates of E. vermicularis in children were 34.0% (33/97), 28.4% (27/95), 30.9% (30/97), 30.9% (46/149) and 20.3% (38/187), respectively. The infection rates of hookworm were 3.6% (41/1 126), 1.0% (11/1 104), 7.4% (76/1 029), 0.9% (9/1 013) and 1.6% (17/1 037), respectively. There were significant differences in the total infection rate and hookworm infection rate among different years (χ² = 114.90, 110.32; P < 0.01). T. trichiura infections were only found in 2016 and 2018. The infection rates were 0.3% (3/1 126) and 0.2% (2/1 029), respectively. The majority of the hookworm infected cases had a mild infection, accounting for 98.1% (151/154). All T. trichiura infected cases were mild infections (5/5). From 2016 to 2020, a total of 115 soil samples were collected. The positive rate of hookworm larvae was 8.7% (10/115), and all were identified to be Necator americanus. No human Ascaris eggs were detected. The positive soils were all from vegetable gardens. From 2016 to 2019, the infection rate of soil-transmitted nematodes in the rural population in Xiangcheng District showed a significant decrease. The E. vermicularis infection in children still remains at high level, and monitoring and prevention should continue to be strengthened.

Key words: Soil-transmitted nematode, Xiangcheng District, Monitoring, Analysis