Abstract: 　AIM:To explore the detection rate and the levels of natural antibodies to cercarial antigen(CA),juvenile antigen(JA),adult worm antigen (AWA) and soluble egg antigen(SEA),respectively,derived from Schistosoma japoncum in Microtus fortis distributed in Dongting Lake area.METHODS:The antibodies in wild Microtus fortis (WMF),laboratory bred Microtus fortis (BMF)and laboratory bred Microtus fortis 15 days after S.japonicum infection (BMF i15 ) were detected by indirect ELISA and a comparison of the antibody levels between Microtus fortis including WMF,BMF,BMF i15 and albino mice without infection (AM), 15 days after infection(AM i15 ) and 42 days after infection (AM i42 ) was made.RESULTS:The positive rates of detection for anti JA Ab in WMF and BMF were 94.6%and 94.4%,respectively,followed by 85.5%and 83.3 % for anti AWA Ab,58.1% and 59.4% for anti SEA Ab,and 14.3% and 13.9% for anti CA Ab.The levels of antibodies to the above four antigens in BMF i15 increased significantly, the detection rates being 100% for anti JA Ab and anti AWA Ab, 84.4% for anti SEA Ab and 65.6% for anti CA Ab.The levels of antibodies in WME, BMF and BMF i15 had the similar trend(JA>AWA>SEA>CA),and those in BMF i15 to CA,JA,AWA and SEA increased by 1.9,2.2,2.1 and 1.5 folds,respectively,when compared with BMF.CONCLUSION:Natural antibodies to Schistosoma japonicum were found in wild and labortory bred Microtus fortis .The levels of antibodies in BMF i15 to four above antigens were apparently higher than those in AM i15 .

Key words: Microtus fortis, Schistosoma japonicum, natural antibody