Abstract:

Objective To understand the infection status of soil-transmitted nematodes at the national monitoring site for soil-transmitted nematode infections in Guizhou Province during 2011-2015. Methods From 2011 to 2015, Tianguan Village of Maguan Town, Dana Village of Pingshang Township, Shuimu Village of Huachu Town, Qingshan Village of Chengguan Town and Pingshang Village of Pingshang Town were selected from the eastern, southern, western, northern, middle parts of Puding County, respectively, as the national monitoring sites for soil-transmitted nematode infections. Surveillance of soil-transmitted nematode infections was performed in one of these villages in each year. Fecal samples from residents aged over 3 were collected and eggs of intestinal nematodes were examined with the Kato-Katz method. The transparent adhesive tape test was used to examine Enterobius vermicularis eggs among children of 3-12 years. A modified floatation test with saturated sodium nitrate was used to detect Ascaris eggs in soil of vegetable field, around lavatory, courtyard and kitchen. The infection rate among residents was analyzed in aspects of gender, age and occupation with Chi square test. Results A total of 5 035 residents were examined from 2011 to 2015, with a soil-transmitted nematode infection prevalence of 14.24% (143/1 004), 15.72% (161/1 024), 12.29% (123/1 001), 15.38% (156/1 001) and 32.44% (326/1 005), respectively. The prevalence of A. lumbricoides (roundworm), Ancylostoma sp.(hookworm), T. trichiura(whipworm) and E. vermicularis (pinworm) in children were 11.40%(574/5 035), 0.62%(31/5 035), 9.33%(470/5 035) and 1.01%(14/1 381), respectively. There was no significant difference in the rate of soil-transmitted nematode infection between males (18.28%, 473/2 588) and females (17.82%, 436/2 447) (χ² = 0.15, P > 0.05). Among different age groups, the infection rate was highest in the 10- year group (23.25%, 381/1 639; χ² = 62.59, P < 0.05). Among different occupations, the infection rate was highest in students (22.46%, 524/2 333; χ² = 58.43, P < 0.05). Among different degrees of education, the infection rate was highest in those with primary school education(1.41%, 455/2 125; χ² = 39.19, P < 0.05). Among different ethnicities, the Miao ethnicity presented higher infection rate (44.99%, 220/489; χ² = 267.70, P < 0.05) than Han and other minorities. Of the 200 soil samples tested from 2011 to 2015, 86 were positive for A. lumbricoides eggs, with a positive rate of 43%. The detection rate of live fertilized Ascaris eggs was highest in soil samples of vegetable field (26%, 13/50) and around lavatory (20%, 10/50), and lowest in those of the kitchen (2%, 1/50), with a significant difference among the four types of soil (χ² = 12.71, P < 0.05). Conclusion From 2011 to 2015, the infection rate of soil transmitted nematodes was still at a high level, mostly roundworm and whipworm. The infection was more significant among people aged 10-20, students, people with primary school education, and the Miao ethnicity. The soils of the living environment showed different degrees of contamination by Ascaris eggs.

Key words: Soil-transmitted nematode, Surveillance, Infection rate, Guizhou Province