Study On Immunization Program For Inactivated Vaccine Against Foot-and-Mouth Disease In Sheep

In recent years, with the implementation of grazing policy by forestry department, the traditional sheep grazing feeding pattern has been gradually replaced by large-scale one. In order to ensure the healthy and sustainable development of sheep industry and safeguard the vital interests of broad masses of peasants, the research in this topic is carried out to study and establish a scientific and reasonable immunization program for inactivated vaccine against foot-and-mouth disease in sheep in line with the actual situation of Yanqing County.By conducting two experiments, vaccine products of good immune effect and cost-effective promotion are selected as objects to carry out immunization programs research. Experiment 1 is to compare the immune effect between combined immunodeficiency of single vaccines against Asian I-type, O-type foot-and-mouth disease and that of divalent ones. Experiment 2 is to study the immunization program for bivalent vaccines against Asian I-type, O-type foot-and-mouth disease.Experiment 1 selects 30 experimental animals which are divided into 3 groups with 10 as a group. Group 1 is for the combined immunodeficiency group of single vaccines against Asian I-type, O-type foot-and-mouth disease; Group 2 is for the divalent vaccines and Group 3 is as a blank control group. Immunity is carried out in accordance with the recommended immunization schedule by vaccine manufacturers, that is to test the maternal antibody at 7,14,21,28,34-day-old respectively;the first immunity is at 35 days old with the tracking test on 7,14,21,28 days after the first immunity. At 65-day-old, the second immunity is carried out with an interval of 30 days; the tracking test is on 7,14,21,28 days after the second immunity; and immunity is carried out every 6 months after the second immunization.O-type foot and mouth disease antibody titers are detected by a positive indirect hemagglutination test, and sub-I-Type foot-and-mouth disease antibody titers are detected by liquid-phase blocking ELISA test. The results show that:combined immunodeficiency group and the divalent group are of the same level basically in the maternal antibody testing and the tracking test after the second and third immunity, so the divalent vaccines are selected as objects to carry out immunization programs research.Experiment 2 selects 20 experimental animals which are divided into 2 groups with 10 as a group. Group 1 is the test group and Group 2 is the blank control group. The immunity time is determined according to the immune antibody level;when it is close to the threshold, carry out the first immunity; conduct an intensified immunity with an interval of 30 days;after that carry out other immunity according to the rise-and-fall situation of antibody. The results show that:test the maternal antibody level at 3,7,14,21,28,42,56 days old respectively; the level in Group 1 of divalent vaccines are relatively low, but the titer can protect the herd; at 56 days old O-antibody level has been basically close to the threshold, and the Asia-I Type antibody level is slightly lower than the threshold. With the combination of practice, the first immunity should be carried out at about 45-day-old; based on principles of immunology and vaccine recommended immunization program, carry out the second immunity 30 days after the first immunity;test the antibody level on Day 14,28,56,116 respectively after the second immunity;at Day 116, O-antibody level is still high,the Asian-I is close to the threshold, carry out the third immunity;test the antibody level on Day 28,56,116 respectively after the third immunity; at Day 116, O-antibody level is high,the Asian-I is close to the threshold,carry out the next immunity.In the two experiments, immune antibody of the blank control group has been of a downward trend until the antibodies disappear, and continue until the end of experiment. As this study has no attacking toxicity test conditions, it can only be judged accordingly that experimental animals are not infected with wild toxic;the immune effects of the vaccine are confirmed based on the antibody test results.Conclusion:Immunization program for Asia-I-O type divalent'vaccine of cows and sheep against foot-and-mouth disease procedures should be:carry out the first immunity at 45day-old with neck or buttocks intramuscular injection of 0.5ml immunization dose; carry out the booster immunization 30 days after the first immunity with 0.5ml dose; every 4 months after that carry out one immunity with 1ml immunization dose.