MULTIPLE CORRELATION ANALYSIS BETWEEN SCHISTOSOMIASIS EPIDEMICS AND ENVIRONMENTAL FACTORS ON THE BASIS OF EMPIRICAL STUDY IN THE ADMINISTRATIVE VILLAGES OF NANCHANG COUNTY

The purpose of this study was to explore the relationship between the schistosomiasis epidemicity and the social,economic,environmental factors in a typical schistosomiasis-epidemic area of the Poyang Lake region.We used simple correlation coefficient,partial correlation coefficient and multiple correlation coefficient,to study the correlations and the interrelationships among the number of infected persons and the five factors of 43 typical schistosomiasis epidemic administrative villages in Nanchang county,Jiangxi province.The five factors were divided into two portions,Infected Water Contact factors(including water contact index,lake border length and distance to the Poyang Lake)and Infected Water Distribution factors(including cattle stock,waters area).The previous studies of water contact index calculation were based on contact ways,contact frequency,the body area exposed and the lasting time without considering susceptible seasons,susceptible time and exposing spots.In the study,we tried to include these important elements into the computation of water contact index in forms of contact way,contact season,the number of contact days,contact time periods in a day,the number of the persons of different contact ways and contact spots.The lake border length and the waters area for each administrative village werederived from a TM image of the Poyang Lake region in June 2009;the distance to the Poyang Lake for each administrative village was measured by length of geometric center of village to the lake border;the cattle stock data was from a social-economic statistic of the Schistosomiasis Control Department of Nanchang county.The simple correlation coefficients between the number of infected persons and the selected 5factors reached 0.05 significance level,among which the water contact factors(including lake boundary length and water contact index)hadhighest correlation coefficients(0.747 and 0.813respectively);the partial correlation coefficients between either the number of infected persons and the water contact factors when fixing the Infected waters factors(including cattle stock,waters area and distance to the Poyang Lake),or the number of infected persons and the infected waters factors when fixing the water contact factors were lower than their simple correlation coefficients,implying there existed mutual interrelationship between the infected waters factors and the water contact factors;the multiple correlation coefficient between the number of infected persons and the whole 5factors was 0.948(P0.005),accounting for 79% of the total variance of the Number of infected persons.Conclusions can be drawn that the selected 5environmental factors were significantly correlated with the number of infected persons;the infected waters factors and the water contact factors were indispensable for epidemic occurrence and there are interrelationship between these 2group factors;the 5macro environmental factors can explain most variance of the number of infected persons.