Winter Weather Factors Impact On The Poyang Lake Region Marshland Snail

Schistosomiasis is one of major parasitic diseases in the south of China, seriously influencing people's health in endemic areas and hindering the development of social economy.Oncomelania hupensis is the only intermediate snail host of Schistosoma japonicum and temperature,as one of the most important environmental factors,directly and indirectly influences breeding and distribution of the snails.Winter temperature determines the survival of snails and average temperature in January in endemic areas is usually higher than 0℃;the durative low temperature is the main reason for the snails unable to live and propagate in the nothern part of China higher than 33°15′N.Temperature between 20℃and 30℃is suitable for the breeding of the snails.At present, more than 94%of the total areas of snail habitats in China locate in lake region of the Yangtze River.With the global warming,the same thing happens in China that brings warmer winters in the south.At the same time,climate warming has caused extreme accidents of weather situation.For example,the heavy snow appeared in Jiangxi in January,2008.Therefore,it is of significance to know about the impact of winter's climate factors on the marshlands of the Poyang Lake region.Land surface temperature(LST) has a closer relationship with the breeding of O.hupensis.With the development of remote sensing technique,it has been more and more applied in distilling LST.Thus on the basis of understanding the impact of temperature changes on the breeding of snails and the relationship between LST from remote rensing,we can apply remote sensing technology to forecast the distribution of snails on the land.Part 1:Endemic situation in experimental areasThere are three experimental areas,the first one is Yaobeicha marshland in Sanmen village,Poyang County in the mideast of the Poyang Lake area,the sencond one is Yangjiaping marshland in Binshan village,Jinxian County in the south of Poyang Lake area,and the third one is two neighbor marshlands,i.e., Majiawan and Zhuxi marshland in Zhuxi village,Xingzi County in the north of Poyang Lake area.The infection rate of residents in Zhuxi village was 3.46%,0.99%,2.25%and 1.90%in 2005,2006,2007and 2008,respectively.The infection rate of residents in Sanmen village was 1.68%,2.33%,0.92%and 0.68%in 2005,2006,2007 and 2008,respectively.The infection rate of residents in Binshan village was 1.23%,0.18%,0.69%and 0%in 2005,2006,2007 and 2008,respectively.No infected snails were found in the three pilot areas in 2007 and 2008.The density of living snail all declined significantly in 2005 and 2008.Part 2:The impact of winter climate' changes on snail habitats in the Poyang Lake region.We collected the climate data including temperature and rain fall of winter months containing December,January and February from 1998 to 2008 and tidied out relative climate variables.Then we carried on the correlative analysis among the climate variables and the variables of snails.In the pilot area of Xingzi,the density of snails showed a negative relationship with the days with the average temperature lower than 5.87℃,the days with average temperature below 0℃and the days with the lowest temperature below 0℃.In winter the density of snails has a positive relationship with the average temperature in January.Percentage of frames with living snail has a positive relationship with the average temperature in December and January.The density of infected snail and the percentage of infected snail both have a positive relationship with the total rain fall in winter.In the experimental area of Poyang County,the density of snails has a positive relationship with the highest temperature in December and average temperature in January.It was the same with the percentage of frames with living snails.The density of infected snails and the percentage of infected snails both had positive relationship with the highest temperature and average temperature in February.In the experimental area of Jinxian,the density of snail had a positive relationship with the average temperature in February.It indicates that the lower temperature in winter in the lake region, the lower density of snails and the percentage of frame with snails.With the higher average temperature in February,it is more suitable for snail to breed; also with that,more frequently,people and cattle begin to go to marshland,and as a result,a higher density of infected snails and a higher percentage of infected snails are shown.Part 3 Exploring the possibility of applying the LST product-MOD11A2 on predicting the situation of snail habitats.The free 8-day LST product-MOD11A2 downloaded from the NASA website,was firstly reprojected and then processed in ENVI.After that,four 8-day LST product-MOD11A2 in January came out the average LST in January.Due to the result in the second part:the density of snails having a positive relationship with the average temperature in January,we cut out the MOD11A2 with the region of investigating snails in Xingzi to get the average LST in January of Xingzi.The result of correlation analysis shows that LST also had a positive relationship with the density of snails with a bigger coefficient 0.929,higher than that between the average temperature and the density of snails in Xingzi,0.764.it suggests that LST retrieved from MOD11A2 can be applied on the mornitoring and predicting the habitat of O.hupensis in the regions that the true LST is difficult to obtain.