湖羊小反刍兽疫母源抗体消长规律及其对羔羊首免日龄的影响

Fluctuation of maternally derived antibody against peste des petits ruminants(PPR)in Hu sheep and its influence to the age of first immunization of lambs

为了评估湖羊小反刍兽疫母源抗体消长情况及其对羔羊首次疫苗免疫接种效果的影响,采用商品化小反刍兽疫病毒阻断ELISA抗体检测试剂盒检测健康母羊产羔当天的母羊血清中、产后不同时间初乳和乳中以及所产羔羊不同时间血清中小反刍兽疫抗体水平;并选取2批羔羊,分别于羔羊21日龄和42日龄或50日龄时,免疫接种小反刍兽疫活疫苗(Clone 9株),监测免疫后不同时间的抗体水平。结果表明:羔羊吮吸初乳后抗体迅速转阳,到49日龄抗体阳性率几乎均为100%,但抗体滴度缓慢下降;母羊乳汁中抗体阳性率5 d时接近70%,7—10 d时抗体阳性率分别为42.9%和53%;母羊生产当天的血清抗体水平与其初乳和乳中抗体水平及其所产羔羊的母源抗体水平均呈正相关(r值分别为0.866±0.128和0.933±0.058)。羔羊免疫试验表明,免疫接种后21 d内,组间的抗体水平无差异,但21—28 d时,A组(50日龄免疫组)及C组(42日龄免疫组)的抗体水平较高,显著优于21日龄免疫组(B组、D组)。湖羊母羊一次免疫接种小反刍兽疫活疫苗后,其所产羔羊母源抗体保护水平至少可维持49 d以上,且母羊生产当天的血清抗体水平与其初乳和乳中抗体水平及其所产羔羊的母源抗体水平均呈正相关;在存在母源抗体的情况下,羔羊过早免疫接种疫苗会严重干扰疫苗接种后的免疫抗体水平及持续时间,故羔羊免疫应根据母源抗体监测情况调整羔羊首免日龄,以保证免疫效果。

To evaluate the fluctuation of maternally derived antibody(MDA)against peste des petits ruminants(PPR)and its influence to antibody levels of lambs vaccinated for the first time,the commercial PPR ELISA kit was used to detect the level of PPR antibody in the blood of healthy pregnant ewes on the day of lambing,colostrum and milk at different time postpartum,and in the serum of their lambs at different time.Two batches of lambs which were randomly selected and not immunized with PPR vaccine were immunized with PPR live vaccine(clone 9 strain)at 21 and 42∕50 days of age,respectively,and the levels of PPR antibody were monitored at different time after immunization.The results showed that the antibody level of lambs quickly turned positive after sucking colostrum,and the antibody positive rate was almost 100%at 49 days of age.The titer of PPR antibody in ewe milk decreased with time,reaching 70%on day 5,and the positive rates of PPR antibody were 42.9%and 53%on day 7 to day 10,respectively.Further analysis showed that the serum antibody levels of breeding ewes on the day of production were positively correlated with antibody levels in colostrum and milk,as well as MDA levels of corresponding lambs produced(r values were 0.866±0.128 and 0.933±0.058,respectively).The lamb immunization test showed that there were no differences in antibody levels between groups within 21 days after immunization,but at 21—28 days,antibody level of group A(50 days of age immunization group)and group C(42 days of age immunization group)were higher,which were significantly better than age of 21 immune groups(group B and group D).The MDA protection level of lambs produced by Hu sheep ewes immunized with PPRV could be maintained for at least 49 days,and the serum antibody levels of breeding ewes on the day of production were positively correlated with antibody levels in colostrum and milk and MDA levels of corresponding lambs produced.In the presence of MDA,premature immunization of lambs with this live vaccine will seriously interfere with the level and duration of immune antibodies after vaccination.Therefore,the first immunizing day age of lambs should be adjusted timely according to the monitoring level of maternally derived antibody to ensure the immune effect.