Preparation And Efficacy Of The Inactivated Oil Emulsion Vaccine Against DRV

A new disease with high mortality in the breeding area of muscovy ducks in the south of china has broken out since 1997--- DRV infections which is usually called muscovy duck's "white spot liver disease" or "flower liver disease" with the infected rate of 20%-90%, mortality rate of 10%-30%, and the mortality would be more than 90% when stressed or co-infected . With the incubation period of one-day-old muscovy ducks inoculated with DRV so short (3～11 days), the easily infected age so young (1¹0days old),and young muscovy duck's immune system too immature to produce enough antibody to protect itself against disease, it's important to gain enough maternal antibody to prevent DRV infections for young muscovy duck. We tried to prepare an inactivated oil emulsion vaccine against DRV and use the vaccine to inoculate seed muscovy duck which may produce the maternal antibody through eggs to protect its offspring against DRV infections, in order to prevent and control the disease.The virus fluid was harvested after the YB strain of DRV was propagated in muscovy duck embryo fibroblasts cells(DEF), which was isolated and kept by our laboratory, of good antigencity and immunogenicity, and was used as seed virus. The virus fluid of high content had been inactivated by 0.3% formaldehyde solution and emulsified by oil emulsion adjuvants, whose TCID50 was for 10^-7.1934/0.1ml, then the inactivated oil emulsion vaccine against DRV came into being.An indirect enzymelinked immunosorbent assay (ELISA) was developed to detect the antibody valence of DRV. The antigen was prepared for ELISA by sodium sulfate centrifugation and precipitation and its virus protein content was up to 0.7355 mg /ml. Negative serum , positive serum (its agar gel precipitation titer is 1: 16), rabbit-duck serum (its AGP titer is 1: 128), HRP enzyme-labeled rabbit-duck IgG were also produced. The optimal reaction conditions were determined. It was shown that the diluting antigen to 1:30, the enzyme-labeled rabbit-duck serum to 1:50, the serum sample to 1:50 were their best working concentrations and the critical OD value was calculated as 0.5 between positive and negative. The highest-level extent of dilution of serum was determined to be its terminal point antibody titer if the diluted serum could produce positive reaction.The inactivated oil emulsion vaccine against DRV prepared was proved to be safe and had no adverse effects for muscovy ducks and couldn't change its immune efficacy after keeping in the refrigerator with 4 ℃ for 3 months. The seed muscovy ducks were vaccinated with the vaccine hypodermically at dosage of 1 ml/duck 10 days before they entered upon their periods for laying eggs . The antibody induced by the vaccine was examined by the indirect ELISA developed above at 0 ,14 d,28 d,42 d,60 d after vaccinated. The results showed that all the sera collected were positive at 14 d after...