| Objective and significance:The Duck tembusu virus?DTMUV?infection in China in2010 is a newly emerged infectious disease of ducks characterized by a sudden drop in egg production and hemorrhagic ovarian inflammation.Currently,inactivated and attenuated live vaccine used in preventing of the emerging disease both showed certain degree of protection against the DTMUV.However,there are many controversies between them on the safety and efficacy for duckling practical use.Aiming at this condition,the safety and efficacy of DTMUV live vaccine and inactivated vaccine were compared and analyzed respectively in this paper,To provide reference for the use of vaccine in the prevention and control of the disease.Methods:Safety and efficacy evaluation of a attenuated vaccine e and inactivated vaccine were characterized with jinding duckling.Sixteen 7-day-old ducklings and sixteen4-week-old ducks were immunized respectively with 3 batches of live vaccine and 3batches of inactivated vaccine at the doses of 0.5ml for each group,while the control group were set as well.The safety of inactivated and live vaccines were evaluated by clinical symptom observation such as weight change,pathological examination after 1 or 2weeks,and histopathological observation such as tissues of brain,liver,and spleen.According to the instructions,routine immunization?intramuscular 0.5 ml for pimary immunization and14 days after that for boost immunization?were carried out on 7-day-old duck and4-week-old duck respectively with 3 batches of live vaccine and 3 batches of inactivated vaccine.Control group without vaccine immunization was set up.Sera were collected from all ducks at 28 days after boost immunization,and duck Tembusu virus HI antibody were detected.Meanwhile,all ducks were challenged intramuscularly with 0.5ml of 100 DID50?50%duck infection dose?of duck tembusu virus.Sera were collected from all ducks on 2days post inoculation and used for virus isolation.All ducks were necropsied at 7 days after virus challange for observation of pathological changes.The protective efficacy of inactivated vaccine and attenuated vaccine against ducklings was studied by histopathological observation.Results:To the safe test of the vaccine,the results showed that,there was a significant difference in weight of ducks between live vaccine immunization group and inactivated vaccine immunization group?P<0.05?,and the geometric mean value is less than the inactivated vaccine group.The histopathological examination showed that many lesions can be viewed in the ducks immunized with live vaccine:the spleen was obviously enlarged,the red pulp was congested and some of the lymphocytes were necrotic,the lymphocytes were necrotic and disintegrating in the white pulp.The liver was slightly enlarged and khaki,the liver cells were fatty degeneration,and the perivascular inflammation was obvious;the brain tissue appeared slight edema and some small blood vessels appeared.Lymphocytic tubes were formed around the kidneys and slight inflammatory cell infiltration was seen in the kidneys.There were no visible lesions but slight fatty degeneration of liver in the ducks of inactivated vaccine group and control group.To the efficacy test of the vaccine,the results showed that,on 2 and 4 weeks post immunization,the titer of HI antibody of live vaccine group was not also higher than that of inactivated vaccine group but earlier,while the inactivated vaccine group can also produce a high level of antibody.The protective rate against the challenge of DTMUVof live vaccine group can reach 91.3%,which higher than 76.48%of the inactivated vaccine group.Conclusion:Immunization of live vaccine on ducklings can induce a certain degree of their immune system injury and lack of growth,whereas no visible pathological changes could be observed in inactivated vaccine group.Immunization of live vaccine induced earlier and higher antibody response than that of inactivated vaccine,furthermore,live vaccine can also provide higher protection rate against the challenge of DTMUV. |
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