关键词: 土源性线虫, 感染, 监测, 云南省

Abstract:

Objective To investigate the prevalence and epidemiological characteristics of human soil-transmitted nematode infections in Yunnan Province, so as to provide insights into formulation of the soil-transmitted nematodiasis control strategy in the province. Methods A total of 17 counties (cities, districts) were selected as surveillance points using a stratified cluster random sampling method according to the requirements of the National Scheme for Surveillance of Liver Fluke and Soil-transmitted Nematodiasis (Trial) (with Lancang County as a fixed surveillance point). Each surveillance point was divided into five eastern, western, southern, northern, and central areas according to geographical locations, and one administrative village was sampled from each area, followed by 200 local permanent residents at ages of 3 years and older sampled for each administrative village as surveillance subjects using a cluster sampling method, with at least 1 000 individuals surveyed in each surveillance point. Subjects’ stool samples were collected, and detected for soil-transmitted nematode infections and egg counts with the improved Kato-Katz thick smear method (two slides for each stool sample). The prevalence and intensity of soil-transmitted nematode infections were calculated, and differences of prevalence were compared with chi-square test. Pinworm eggs were additionally detected among children at ages of 3 to 9 years with a cellophane tape test. Five households were randomly sampled from each administrative village at fixed surveillance points, and one farmland or vegetable garden soil sample was collected from each household to detect hookworm larvae and human Ascaris lumbricoides eggs in soil samples. Results A total of 17 554 residents were detected for soil-transmitted nematode infections in 17 counties (cities, districts), and the prevalence of soil-transmitted nematode infections was 2.81% (493/17 554). The highest prevalence of soil-transmitted nematode infections was seen in southern Yunnan Province (5.27%, 384/7 288) (χ² = 297.64, P < 0.05), and the prevalence of soil-transmitted nematode infections was higher in border counties (11.69%, 370/3 166) than in non-border counties (0.85%, 123/14 388) (χ² = 1 115.42, P < 0.05). As of surveillance points, the highest prevalence was recorded in Lancang County (23.87%, 263/1 102) (χ² = 2 094.64, P < 0.05). The prevalence of soil-transmitted nematode infections was 2.60% (214/8 237) in males and 2.99% (279/9 317) in females, and the highest prevalence was observed among individuals at ages of 60 to 69 years (3.72%, 99/2 658) (χ² = 47.97, P < 0.05). As of ethnicity, Jingpo (1/2), Lahu (27.68%, 155/560), Hani (14.74%, 102/692), and Wa (12.66%, 10/79) ethnic populations had the four highest prevalence of soil-transmitted nematode infections (χ² = 1 828.99, P < 0.05), and in terms of occupations and educational levels, the highest prevalence was seen among farmers (3.37%, 457/13 563) (χ² = 71.94, P < 0.05) and illiterate individuals (6.71%, 89/1 327) (χ² = 143.84, P < 0.01). The prevalence of hookworm, A. lumbricoides, Trichuris trichura, and pinworm infections was 2.47% (434/17 554), 0.05% (9/17 554), 0.26% (45/17 554), and 0.07% (13/17 554), respectively. The prevalence of mild and moderate infections was 97.00% (421/434), 8/9, and 88.89% (40/45), and 1.38% (6/434), 1/9, and 11.11% (5/45) among individuals with hookworm, A. lumbricoides, T. trichura infections, respectively, and the prevalence of severe infection was 0.38% among individuals with hookworm infections (0.38%, 6/434), while no severe infections were found among individuals with A. lumbricoides or T. trichura infections. A total of 25 soil samples were detected for hookworm larvae and A. lumbricoides at fixed surveillance points, and the detection of hookworm larvae was 44.00% (11/25); however, no A. lumbricoides eggs were detected. In addition, tapeworm, Trichostrongylus orientalis, and Hymenolepis diminuta infections were detected. Conclusion The prevalence of soil-transmitted nematode infections is high in ethnic minority border regions of Yunnan Province, notably hookworm infections. Implementation of integrated soil-transmitted control interventions should be given be a high priority in future parasitic disease control programs in ethnic minority border regions of Yunnan Province.

Key words: Soil-transmitted nematode, Infection, Surveillance, Yunnan Province