Abstract:

To understand the prevalence and transmission of soil-transmitted helminth (STH) infection in Gongshan County. From 2016 to 2021, according to the National Surveillance Program for Liver Fluke Diseases and Soil-transmitted Nematodes (Pilot). The Gongshan County were selected from five areas (east, west, south, north and central). From each of the areas, a township was randomly selected, and then an administrative village was selected from each township as the surveillance site every year. Over 200 permanent residents above 3 years old were cluster sampled from each administrative village and no less than 1 000 residents were included every year. Fecal samples were collected from the participants for examining and counting STH eggs using the modified Kato-Katz thick smear method to calculate the infection rate. Hookworm egg-positive samples were further identified for species by test tube-filter paper culture method. The eggs of Enterobius vermicularis were detected by the cellophane tape method in children aged 3-9 years. The species and number of infected were recorded, and the infection rate was calculated. The infection rate between groups was compared by the Chi-square test. The fecal samples from 6 175 residents were examined with 928 samples infected with STH. The total infection rate was 15.03% (928/6 175). The infection rates of hookworm, Ascaris lumbricoides, whipworm and Enterobius vermicularis were 3.27% (202/6 175), 7.92% (489/6 175), 8.87% (548/6 175) and 0.19% (12/6 175) respectively. The E. vermicularis eggs were detected by the cellophane tape method in children aged 3-9 years. A total of 823 children were examined and 6 were infected. A total of 202 cases of hookworm infection were identified by the test tube filter method. Among them, 89 cases were infected with Necator americanus, 72 cases were infected with Ancylostoma duodenale and 1 case was infected with both, accounting for 44.06% (89/202), 35.64% (72/202) and 0.50% (1/202), respectively. Minor with hookworm, A. lumbricoides and whipworm infections accounted for 81.19% (164/201, 69.33% (339/489) and 78.29% (429/548) respectively. From 2016 to 2021, the infection rate of STH in Gongshan County was 38.78% (389/1 003), 14.76% (156/1 057), 6.53% (68/1 042), 13.15% (134/1 019), 11.89% (121/1 018) and 5.79% (60/1 036), respectively. There was significant difference in the infection rate among different years (χ² = 581.98, P < 0.01). Among the five townshipssurveyed, the infection rate of STH was the highest in Dulong River township (32.07%, 398/1 241), and the lowest in Cikai town (9.09%, 112/1 232).The infection rate of STH was statistically significant among different village (χ² = 359.24, P < 0.01). The infection rate of STH was 11.20% (291/2 598) in male and 17.81% （637/3 577) in female, with significant difference (χ² = 51.49, P < 0.01). The STH infections were found in all age groups with the highest infection rate in the age group 3 to 9 years old (28.21%, 244/865). People of the Dulong ethnic group had the higher STH infection rate of 30.39% (392/1 290) than people with other ethnic groups. Children possessed the highest infection rate of 27.78% (170/612) compared with people with other occupations. In terms of education, the STH infection rate was highest among preschool child 27.48% (169/615). The infection rate of STH was statistically significant among different agegroups, nationalities, occupations and educational levels (χ² = 172.16, 310.89, 195.59, 197.59; P < 0.05). The results showed that the infection rate of STH in Gongshan County decreased significantly from 2016 to 2021, but remained at a high level. Combined with the rural revitalization project, the comprehensive control of STH should be continued to strengthen among key populations such as Dulong nationality, children and the elderly.

Key words: Soil-transmitted helminth, Infection rate, Surveillance, Gongshan County