Abstract:

Objective　To understand the endemic situation of soil-transmitted nematodes in Luoyang City from 2017 to 2020,so as to provide evidence for developing targeted prevention and control measures in local areas.Methods　In accordance with the requirements specified in the National Surveillance Program for Liver Fluke Diseases and Soil-transmitted Nematodes(Trial) and Surveillance Plan for Soil-transmitted Nematodes and Implementation Rules of Henan Province,we established mobile monitoring sites in the 9 counties(districts),including Yichuan County and Luolong District,under administration of Luoyang City from 2017 to 2020. Each monitoring site in individual county/ district was divided into 5 areas by geographical location(east,west,south,north and middle areas),where one administrative village was selected from a township to undergo surveillance. In addition,no less than 200 permanent residents aged over 3 years were annually included by cluster sampling from each administrative village,and totally no less than 1 000 people were included from each surveillance site. Fecal samples were collected from all participants,and examined for the egg count of soil-transmitted nematodes using modified Kato-Katz thick smear technique(one sample for two smears). Children aged between 3 and 9 years old were given additional detection of the eggs of pinworm by anal swab test with cellophane tape. The roundworm eggs in the soil samples were detected and counted using the saturated sodium nitrate solution floatation method.Results　A total of 9 296 people were surveyed from 2017 to 2020. The infection rate of soil-transmitted nematodes was 2. 48% (231/9 296),in which pinworm infection was 97. 40%(225/231). The infection rate was 0. 04% (4/9 296),0. 01 % (1/9 296),0. 01%(1/9 296) and 2. 42% (225/9 296),respectively for roundworm,hookworm,whipworm and pinworm,and the highest infection with pinworm was seen in population in Luoning Country. There was no statistical difference in infection between males and females,yet the difference was significant in pinworm infection in different age groups(χ 2 = 49. 520,P<0. 05), with the highest in children aged between 3 and 10 years old,followed by population over 60 years. The infection rate of pinworm was statistically significant in people with diverse occupations(χ 2 = 27. 734,P<0. 05),and the highest in preschool children and elementary students. Infection with pinworm tended to decline in population with increased level of education(χ 2 =30. 638,P<0. 05). Anal swab and modified Kato-Katz thick smear tests respectively revealed infection rate of pinworm being 3. 95% (76/1 925) and 4. 40% (89/2 021) in children between 3 and 9 years old,and additional modified Kato-Katz thick smear test demonstrated that the infection with pinworm was 1. 91%(136/7 275) in children aged from 3 to 9 and over 9 years old. The difference was significant (χ 2 =41. 946,P<0. 001). Fertilized and unfertilized eggs of roundworm were detected in the soils sampled from the monitoring sites,yet the detected rate was low.Conclusion　pinworm is the dominant species of soil-transmitted nematode diseases in population in Luoyang City,and affects the most in residents in Luoning County. Children and the aged should be the key population in following prevention and control of soil-transmitted nematodes.

Key words: Soil-transmitted nematode, Pinworm, Surveillance, Luoyang City