Report On Soil-transmitted Helminths Infections And Its Risk Factors In People’s Repulic Of China

Objects Soil-transmitted helminth (STH) infection rates re-main high in mainland China. This study aimed to describe the epidemic characterizes of infection in China and testing the relationship between environmental and social-economic factors with STH infection, in order to find risk and protective factors to provide scientific clues for decreas-ing STH infection rate. Methods In the eight baseline investigation sites in2006, a standard questionnaire including information about sex, age, nationality, occupation, education experience, source of drinking water, washing hand after using the toilet, eating unwashed fruit, going barefoot, and using different dishes for raw and cooked food was determined for each subject. In each of the22surveillance sites, one village with a pop-ulation of more than1,500was chosen for the investigation from2006to2009. In addition to data on STH infection, information on hygienic dis-posal of feces, annual family income, elevation, annual average tempera-ture, annual average relative humidity, annual precipitation, and annual hours of sunlight was collected. The climate factors such as temperature, humidity, hours of sunlight and precipitation were collected from mete-orological monitoring sites in the surveillance areas. The subjects pro-vided information on average yearly income, and elevation was measured in the field. A database was established using SPSS18.0(SPSS Inc., Chicago, IL, USA). The data were geo-coded and underwent Kriging in-terpolation in ArcGIS software to conform to the area of the study. Each of the baseline investigation sites and surveillance sites was geo-referenced at the counties level and the data were linked to a digital map at a scale of1:100,000using ArcGIS9.2software (ESRI Inc., Red-lands, CA, USA). To identify individual risk factors associated with STH infections, unconditional logistic regression analyses were performed on baseline investigation data of A.lumbricoides, hookworm and T. trichiura infections using SPSS18.0(SPSS Inc.). To explore the factors influenc-ing the prevalence rate of STH infections at a population level, mul-ti-level Poisson regression was performed based on the data of the22 surveillance sites during2006-2009. Results1Spatial Distribution of STH Infections in China. A total of90,957people were investigated from2006to2009in22surveillance sites. The mean annual prevalence of A. lumbricoides, hookworm and T. trichiura infection was9.0%,7.6%and5.9%, respectively in mainland China. Three counties in southwestern China in Yunnan, Jiangxi and Guizhou provinces, had the highest overall prevalence rates of STH infections (56.5%,27.2%and24.2%, respec-tively). Counties in Heilongjiang, Beijing, Shanxi and Hebei Provinces in northeastern and northern China had the lowest overall prevalence rates of STH infections (close to0%). The highest prevalence rates of A. lum-bricoides and T. trichiura infections were in Menghai county in Yunnan province (72.8%and59.8%, respectively). The highest prevalence rate of hookworm infection was in Xiangcheng County in Fujian Province in southeastern China (36.9%). Figure2shows the spatial distribution of prevalence rates of STH infections in mainland China in this survey. The prevalence rates of STH infections in southern China were higher than those in northern China.2Individual Risk Factors for STH Infections. A total of17,321subjects were tested for STH infections in the seven base-line investigation sites in2006. The overall infection rates for A. lumbri-coides, hookworm and T. trichiura in the baseline investigation sites were16.8%,21.1%, and5.5%, respectively. Logistic regression analysis showed that individual STH infections were associated with personal living habits including not hand-washing after using the toilet and eating unwashed fruits. However, the effects of sex, age, occupation, education and source of drinking water on the three STH infections were heteroge-neous. Multivariate analyses showed that sex and age had no significant effects on the prevalence of A. lumbricoides and T. trichiura infections, but that females and older subjects had a higher risk of hookworm infec-tion. Ethnicity (other ethnicities versus Han ethnicity) had different ef-fects on the three STH infections with a positive influence on hookworm infection but no significant effect on A. lumbricoides and T. trichiura in-fections. Regarding occupation, children and students had a higher risk of T. trichiura infection than peasants, but peasants had a higher risk of hookworm infection. For education, illiterate subjects had a higher risk of T. trichiura infection, but a lower risk of hookworm infection. In addition, drinking well or surface water was associated with a higher risk of A. lumbricoides and hookworm infections, but not of T. trichiura infection. The two influencing factors related to personal living behavior, not hand-washing after using the toilet and eating unwashed fruits were asso-ciated with similar increased prevalence rates of the three STH infections. However, subjects who often went barefoot had a higher risk of hook-worm and T. trichiura infections, but a lower risk of A. lumbricoides in-fection. Multi-level Poisson regression showed that the prevalence of A. lumbricoides infection was significantly associated with elevation, unhy-gienic disposal of feces, lower income, presence of A. lumbricoides eggs in yard soil, and meteorological factors, including temperature, humidity, precipitation and hours of sunshine. Hookworm infection was associated with unhygienic disposal of feces, temperature, humidity and hours of sunshine, while T. trichiura infection was only associated with yearly in-come. Conclusions The spatial distribution of STH infections suggests that intervention measures need to be focused on southern China. The heterogeneous effects of risk factors at both individual and population levels indicate that it is necessary to target prevention and control measures for each STH infection.