A Study On The Suitability Of O.h.r. Yunnan Strain Snail

Objective:For the purpose of perfecting the theoretical foundation of O.h.r.yunnan strain and provding scientific evidence to control the prevalence schistosomiasis effectively. The thesis is designed to study the suitability extent of O.h.r.yunnan strain snail which is the only intermediate host of the snail under laboratory condition by testing the hibernation temperature and lethal temperatures in summer and winter of O.h.r.yunnan strain.Methods:To test the hibernation temperature, the lethal temperatures in summer and in winter of O.h.r.yunnan strain snail which were collected from the Yunnan mountainous regions, the experiment adopted the method of changing the temperature progressively. The the high amd low lethal temperatures and hibernation temperature was analysed by using method of linear regression to get the high and lethal temperature of LT50,and hibernation temperature ET50, and fitting logistic curve.Results:The lethal temperatures in summer:the snail began when the temperature reac-ed 37℃.the mortality of dry group and wet group is significantly high when the temper-ature reaced 40℃. Drying group snails and wet group snail were all died in the temperature of 43℃and 44℃.The lethal hyperthermy temperatures of 50% O.h.r.yunnan strain in dry and w-et environment was 40.041℃(95% of confidence interval from 39.424 to 40.680℃) and 41.230℃(95% of confidence interval from 40.430to 42.190℃), respectively.The logistic regression equations between temperature and mortality were: Yd=101/(1+e42.274-1.064X) (F=116.422,P<0.01);Yw=101/(1+e39.926-0.978X) (F=65.125,P<0.01).Hibernation temperature:Accorroding to the surrounding temper-ature declining to 13℃.the Activities of snal becomes less.and the closed snail more.as to 2℃, Percent of snails with close is 100%。As to about 11℃,part of snail begin to app-ear hibernation.as to 0℃, the Percent of snails in hibernation is 100%.The hibernation temperature of 50% O.h.r.yunnan strain snail was 5.312℃with the (95% of confidence interval from 4.771 to 5.832℃); The logistic regression equation between temperature under 13℃and hibernation rate of O.h.r.yunnan strain snail was Y=101/(1+e0.668x4.13) (F=415.383.P<0.01).55%moisture.non-immersion environment:Under the dry and wet environment when the temperature down to 0℃, the snail begin to die and the two group snail all die at the temperature of-7and-8 The lethal temperature of 50% O.h.r. yunnan strain snai was-2.794℃in dry environment (95% confidence interval from-3.024to-2.562℃), and-3.712℃in w et environment (95% confidence interval from-3.968 to-3.456℃); Yæ½®=101/(1+e0.975x+3.76) (F= 132.002, P< 0.001).their logistic regression equat ions could be expressed in Yd=101/(l+e1.029+2.987x) (F=347.84, P< 0.001)Yw=101/(1+e0.975x+3.76) (F=132.002, P<0.001). 75%moisture,inmersion enviroment:When the temp down to-1℃,the mortal in the d-ry and wet environmen,isl3.3% and 60.0%.(X2= 28.134, P<0.0001 The lethal temper-ature of 50% O.h.r.yunnan strain snai was-3.371℃in dry environment (confidence int-erval from-3.810to-2.929℃)å'Œ-1.085℃in wet environment (95% confidence interval from-2.203 to0.349℃).Conclusions:(I) The temperature of the beginning of the hibernation of O.h.r.yunnan strain snail is 12℃. (2) The survivability of O.h.r.yunnan strain snail at ultimate high and low temperatures is weaker in dry environment than in wet environment. (3) There is no difference in survivability between O.h.r.yunnan strain snail and O.h.hupensisi at ultimate high and low temperatures. (4) Humidity has a significant effect on the death rate of O.h.robertsoni if the temperature drops below 0℃.