Abstract:

Objective To understand the infection status of soil-transmitted helminth (STH) at national surveillance sites in Qinghai Province from 2016 to 2020 to provide a scientific basis for formulating prevention and control strategies. Methods National surveillance sites were set up in 29 counties (cities, districts) in Qinghai Province during 2016—2020, comprising 2 fixed surveillance sites and 5-6 mobile sites every year. 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 3 years old. Fecal samples of residents were collected and examined for STH eggs with the modified Kato-Katz thick smear method (two slide-reading for each sample). At the same time, children aged 3-9 years were examined for Enterobius vermicularis eggs using cellophane anal swab method. The infection rates and infection intensity were calculated. The distribution of gender, age, ethnic group, occupation and region of the infected population were analyzed. The Chi-square test was used to compare the infection rate between different groups. Results A total of 37 724 residents were examined during 2016—2020. The overall infection rate of STH was 0.86% (323/37 724), with Ascaris lumbricoides is the main pspecies, accounting for 99.69% (322/323) of the total infected. The infection rate of A. lumbricoides was 0.85% (322/37 724), including 87.89% (283/322) mild infection and 12.11% (39/322) moderate infection. The infection rate of En. vermicularis was 0.02% (1/4 069) in children aged 3-9 years. The infection rates of STH in males and females were 0.80% (148/18 550) and 0.91% (175/19 174), respectively, with no statistically significant difference(χ² = 1.611, P > 0.05). The 3-10 years old group had the highest infection rate of STH (1.42%, 90/6 351), with statistically significant in different age groups (χ² = 43.516, P < 0.01). The Han ethnic group had the highest infection rate of STH (1.66%, 276/16 622), with statistically significant differences in different ethnic groups (χ² = 242.302, P < 0.01). Migrant workers had the highest infection rate of 2.82% (5/177), with statistically significant differences among different occupations (χ² = 178.710, P < 0.01). From 2016 to 2020, the infection rate of STH in Pin’an County was 1.21% (24/1 086), 3.37% (39/1 157), 1.70% (17/1 000), 1.19% (13/1 091) and 0.89% (9/1 003), the differences between years were statistically significant (χ² = 25.239, P < 0.01). The infection rate of STH in Huzhu County was 1.81% (18/994), 2.47% (24/971), 2.28% (23/1 007), 3.01%(30/998) and 2.37% (24/1 012), showing a fluctuated changes, with no significant difference among them (χ² = 3.132, P > 0.05). From 2016 to 2020, 103 residents with STH infection were found in 27 mobile surveillance sites, of which 99 infected residents (96.12%) were found in the Qilian Mountains and Hehuang Valley. No infected resident was found in the Caidamu Basin. The difference in infection rates among different regions was statistically significant (χ² = 378.856, P < 0.01). Conclusion The infection rate of STH was considerably low in surveillance sites in Qinghai Province, mainly with A. lumbricoides infection. Children aged 3-10 years old and migrant workers are the key groups for prevention and control in the future.

Key words: Qinghai Province, Soil-transmitted helminth, Infection, Surveillance