[Strengthening the research and application of spatial epidemiology to promote precise prevention and control of parasitic diseases in China].

Spatial epidemiology is a new branch of epidemiology, and is a subject that mainly analyzes the geographical distribution and changes of population health or diseases and its related impact factors. Recently, spatial epidemiology has been extensively applied in the prevention and control of parasitic diseases in China, and delightful results have been achieved. However, the research and application of theories and methods of spatial epidemiology are still needed to protect the people's health in China.

[Progress of spatial epidemiology applied to prevention and control of schistosomiasis].

Schistosomiasis is one of the key diseases of surveillance and prevention in China. The elimination of schistosomiasis is of great significance to people's health and social economy. With the development of spatial epidemiology, progress has been made in the spatial distribution of schistosomiasis, the prediction of spatial and temporal trends, and analysis of the environmental factors. This paper reviews the application of spatial epidemiology in the control and prevention of schistosomiasis and introduces the spatio-temporal distribution methods, spatial model, and application of remote sensing technology.

[Relationship between natural extinction of Oncomelania hupensis snails and water chemical properties in Eastern Dongting Lake areas].

OBJECTIVE: To investigate the reasons of natural extinction of Oncomelania hupensis snails by comparing the difference of the water chemical properties between the snail-breeding marshland and non-snail marshland in Eastern Dongting Lake areas. METHODS: Three adjoining marshlands in Eastern Dongting Lake areas were selected, one was a snail-breeding marshland, the second was a non-snail marshland, and the third was a boundary zone between them. During the periods of water-rising season, wet season and water-falling season, the water samples from the bottom of 0.5 m were collected by the systematic random sampling method (200 m × 200 m grid method). In addition, the water samples below the surface of 0.5 m were also collected in the wet season. The physicochemical indexes of the sampling water were detected. RESULTS: According to the Surface Water Environmental Quality Standard (GB 3838-2002), the water quality indicators which were less than the detection limit were Cr, Cd, Zn, Hg, Cu, S－ and CN－ during the three sampling seasons. The pollutants which were slightly higher than Grade III but lower than Grade IV (Hg ≤ 1 µg/L, TP ≤ 0.1 mg/L) were Hg and TP. The pollutants below the Grade III included As and F－. The temperature and pH values were within the Grade III. The oxygen consumption indicators covering DO, COD and BOD in the water-rising season and wet season were within the Grade III, while the value of BOD was beyond the scope of Grade III but was between Grade Ⅳ (≤ 6 mg/L) and Grade V (≤ 10 mg/L) in the water-falling season. The differences of the water pollution indexes between the snail-breeding marshland and non-snail marshland were statistically significant, and these indexes included F－, As and pH in the water-rising season (P < 0.05); pH, BOD and Fat the surface layer in the wet season (P < 0.05); F－ at the bottom in the wet season (P < 0.05); TP and F－ in the water-falling season. Moreover, the above-mentioned indexes in the non-snail marshland of Qianliang Lake were higher than those in the snail-breeding marshland of Junshan Park. Thus, F－ was the only index which had statistical differences in every sampling season, and the concentration of F－ at the non-snail marshland was also higher than that at the snail-breeding marshland. In the water-rising season, the pH value at the non-snail marshland exceeded the suitable range for the growth of snails (6.8 to 7.8). CONCLUSIONS: In the Eastern Dongting Lake area, the high concentration of F－ and pH of water may be responsible for the natural extinction of O. hupensis snails.

[Evolution and evaluation of schistosomiasis prevention and control institutions in China].

Schistosomiasis is one of a few endemic and infectious diseases, which are controlled by the specific prevention and control institutions in China. Through the review of historical data, this paper describes the construction, continuation and changes of schistosomiasis prevention and control institutions in different historical periods and systems, and analyzes and evaluates its historical function, contribution and status.

[Measures and achievements of schistosomiasis control in the Yangtze River Basin].

This paper reviewed the prevention and control of schistosomiasis in the Yangtze River Basin in three stages, centered on the measures and achievements. It pointed out the key work of prevention and control which are infectious source control and effective surveillance at present stage. It will be beneficial to schistosomiasis control in China.

[Knowledge of schistosomiasis in traditional Chinese medicine].

Schistosomiasis is a modern disease name, but it has been widespread in ancient China and exists in a specific form in traditional Chinese medicine (TCM) . The purpose of the paper is to make clear the existing form of schistosomiasis in TCM and infer the prevalence of schistosomiasis in ancient China. The paper focuses on the period when great progress was made on schistosomiasis by TCM, and sums up the understanding of TCM toward schistosomiasis in this period. By studying and analyzing the literature of schistosomiasis in this period, the paper tries to find out the representative Chinese medicine symptom description and TCM "other name" of schistosomiasis, so as to accurately judge whether the relevant description in ancient TCM books and historical documents can provide scientific basis for schistosomiasis. It is important to understand the prevalence and cognition of schistosomiasis in ancient China.

[Temporal and spatial distribution of Schistosoma infection of population and its risk factors in Eastern Dongting Lake area in 2012 and 2014].

OBJECTIVE: To investigate the temporal and spatial distribution of Schistosoma infection of population and its risk factors in Eastern Dongting Lake area in 2012 and 2014, so as to provide the reference for formulating effective intervention measures. METHODS: Junshan District was selected as a study field in Eastern Dongting Lake area. The method of spatial autocorrelation analysis was applied to analyze the change of spatial distribution of Schistosoma infection in Junshan District in 2012 and 2014. The spatial regression model was fitted to detect the risk factors for human infection. RESULTS: The livestock infection rate in 2013 was lower than that in 2011. The average infection rate of schistosome was reduced to 0.55% in 2014. The spatial autocorrelation existed on the distribution of schistosomiasis in Junshan District in both 2012 and 2014 and 4 high incidence villages were identified. The results of the spatial error model showed that the prevalence of human infection was positively correlated with the infection rate of the livestock and the area of the susceptible environment in 2012. The spatial lag model showed that the prevalence of human schistosomiasis was positively correlated with the area of the susceptible environment, but not with the infection rate of livestock. CONCLUSIONS: The measures involving grazing prohibition and phasing out cattle and sheep are remarkably effective and should continue on the basis of the current spatial distribution of schistosomiasis in this area.

[Research on living status of Oncomelania hupensis in autumn and winter and its correlates in Eastern Dongting Lake area].

OBJECTIVE: To explore the dynamic changes of Oncomelania hupensis snail densities in autumn and winter and the relationship between hydrological and meteorological factors and snail growth and decline. METHODS: From Octobers to Decembers of 2007 to 2014, a bottomland close to eastern Dongting Lake was selected as the study field. The snails and elevation of the points were surveyed, and the hydrological and meteorological data were collected. The snail densities and death rates of every month were calculated. The meteorological and hydrological data were described, and the relationship between the snail densities and associated factors were fitted by the multiple regression model. RESULTS: The snail density was highest in October 2012 (41.88 per 0.1 m2) and lowest in November 2008 (1.23 per 0.1 m2). The snail mortality was highest in November 2008 (73.72%) and lowest in October 2012 (1.09%). The multiple regression model found a linear relationship between hydrological and meteorological factors and snail densities. The correlation coefficient between the prediction of ln (snail density) and its measurements by using this model was 0.927 (P = 0.001). CONCLUSIONS: The average minimum temperature in January and time of starting flood have an obvious influence on the snail densities in autumn and winter.

[Distribution features of wild feces in schistosomiasis endemic areas in Jiangling County, Hubei Province].

OBJECTIVE: To understand the spatial distribution characteristics of wild feces in schistosomiasis endemic areas of Jiangling County, Hubei Province and further explore the source of infection efficiently, so as to provide the evidence for the development of corresponding monitoring and response technology. METHODS: In 2011, the fresh wild feces were investigated every two months in the selected 15 villages by the severity of historical endemic in Jiangling County. The schistosome miracidium hatching method was used to test the schistosome infection of the wild feces. The descriptive analysis and spatial analysis were used for the description of the spatial distribution of the wild feces. RESULTS: Totally 701 wild feces samples were collected with the average density of 0.055 6/100 m2, and the positive rate of the wild feces was 11.70% (82/701). The results of the regression analysis showed a positive spatial correlation between the positive rate of wild feces and the rate of human infection, the area with infected Oncomelania hupensis and the number of fenced cattle, and the corrected R2 of the model was 0.58. CONCLUSIONS: The infection rate of wild feces is positively correlated with the rate of human infection, area with infected O. hupensis and number of fenced cattle in space in Jiangling County, so the prevention and control measures could be conducted according to the spatial distribution of the positive wild feces.

[Cost-effectiveness of comprehensive schistosomiasis control strategy with focus on cattle and sheep removal in Junshan District, Yueyang City].

OBJECTIVE: To evaluate the cost-effectiveness of comprehensive schistosomiasis control measures with focus on total removal of cattle and sheep in Juanshan District, Yueyang City. METHODS: The schistosome infection status of human, cattle, sheep and Oncomelania hupensis snails and costs of control measures were gathered during the period of 2006 to 2016. The costs for different periods and cost-effectiveness ratios were calculated. RESULTS: The prevalence of schistosome infection in residents in the pilot villages decreased from 3.44% in 2006 to 0 in 2016. The annual costs of schistosomiasis prevention and control were 4 708 500 yuan from 2006 to 2008, 5 094 700 yuan from 2009 to 2012 and 9 522 700 yuan from 2013 to 2016. The cost-effectiveness analysis showed that the average annual cost of reduction in the residents'infection rate by 1% were 79 500 yuan from 2006 to 2008, 101 200 yuan from 2009 to 2012, and 95 200 yuan from 2013 to 2016, respectively. CONCLUSIONS: The comprehensive schistosomiasis control strategy with focus on cattle and sheep removal in Junshan District is cost effective which could be extended to other lake and marshland schistosomiasis endemic areas.

[Pattern analysis of tempo-spatial distribution of schistosomiasis in marshland epidemic areas in stage of transmission control].

OBJECTIVE: To investigate the tempo-spatial patterns of schistosomiasis in Jiangling County, Hubei Province, so as to identify the risk areas and provide the scientific evidence in following intervention plans for marshland epidemic areas in the stage of transmission control. METHODS: The schistosomiasis epidemiological data in Jiangling County from 2009 to 2013 together with the related geographical information were collected and analyzed. The tempo-spatial distribution patterns were analyzed by the spatial autocorrelation analysis and spatial clustering analysis. RESULTS: The human infection rate was decreased from 2.15% in 2009 to 0.63% in 2013, which was the historically low level. The results of tempo-spatial analysis showed that there were spatial clustering effects in human schistosomiasis infection for each of the years. The values of spatial autocorrelation index Moran's I were statistically significant. Eighteen and thirty-five clusters were detected by using SatScan and FlexScan software, respectively. CONCLUSIONS: From 2009 to 2013, the schistosomiasis endemic situation in Jiangling County presented a decline trend and reached the historical low level. The identified spatial clustering areas should be targeted as the prioritized areas for schistosomiasis control.

[Investigation on prevalence and risk factors of HIV/AIDS and Schistosoma japonicum, Ascaris lumbricoides and Trichuris trichiura infections in a rural community of southwestern China].

OBJECTIVE: To investigate the prevalence and risk factors of helminthic infections including Schistosoma japonicum, Ascaris lumbricoides and Trichuris trichiura and human immunodeficiency virus (HIV), and find out the association among them in a rural community of southwestern China. METHODS: A community-based cross sectional study was conducted. One town was selected randomly; the infections of S.japonicum, A.lumbricoides and T.trichiura were detected with the modified Kato-Katz thick smear method and HIV infection with the diagnostic Test Kit among all residents. A questionnaire survey was conducted to investigate the related risk factors. RESULTS: Among the participants, the infection rates of HIV, S.japonicum, A.lumbricoides and T.trichiura were 2.33%, 2.05%, 13.47% and 30.59% respectively; 7.08% (31/438) were infected with both A.lumbricoides and T.trichiura; 0.23% (1/438) were co-infected with HIV and A.lumbricoides, and the same with HIV and T.trichiura. The multivariate logistic regression analysis showed that sex (male, OR=3.26, 95% CI：0.97, 10.95) and drug abuse (OR=72.86, 95% CI：18.51, 286.76) were significantly associated with HIV infection. Home toilet was negatively related to A.lumbricoides infection (OR=0.52, 95% CI：0.27, 0.98) and T.trichiura infection (OR=0.48, 95% CI：0.28, 0.80). Compared with the people in Villages Four, the people living in Village One were at a higher risk for A.lumbricoides infection (OR=3.14, 95% CI：1.35, 7.27), and compared with the people living in Village Four, the people living in Village Two and Village Three were more likely to be infected with T.trichiura (OR=3.73, 95% CI：1.92, 7.26; OR=4.53, 95% CI：2.12, 9.68). The people aged between 11 and 20 years had a higher T.trichiura infection risk than the people aged more than 50 years (OR = 3.72, 95% CI：1.59, 8.67). There was a significant association between A.lumbricoides and T.trichiura infections (OR = 3.11, 95% CI：1.63, 5.93). There was no association between S.japonicum infection and related factors above mentioned. CONCLUSIONS: The infection rates of HIV, S.japonicum, A.lumbricoides and especially T.trichiura were rather high in this area, and therefore, the prevention and treatment of these diseases should be strengthened. Further studies on the relationship between HIV and the infections of helminths, especially S.japonicum are needed.