Inactivated vaccine for protection against duck virus enteritis

Immunogenicity of inactivated tissue-culture-derived duck enteritis virus (DEV) vaccines was evaluated in white Pekin and mallard ducks. DEV from a Lake Andes outbreak was propagated in chicken embryo fibroblast cells, inactivated with beta-propiolactone, and emulsified with Freund's adjuvant (FA), multiple-oil emulsion (MOE), or Squalane-pluronic L121 (L121). White Pekin and mallard ducklings were vaccinated at 2 or 3 wk of age, respectively. Challenge at 2 wk postvaccination with a virulent DEV isolated from a Long Island outbreak indicated that inactivated Lake Andes (ILA) vaccine mixed with any of the above adjuvants conferred protection, even with a single-dose inoculation. Antibody responses to vaccination, as determined by indirect enzyme-linked immunosorbent assay, showed that ILA virus with FA induced an early production of antibodies similar to that induced by commercially available modified live virus (MLV) vaccine. However, the mean anti-duck virus enteritis (DVE) IgG titers determined by multiple samplings during the first 35 days postvaccination showed titers from ILA virus with FA to be at least 10 times higher than those induced by MLV vaccine. The highest antibody titers were induced by ILA mixed with FA followed by ILA mixed with the MOE and L121. The results of this study indicated that inactivated vaccine is as efficacious as modified live vaccine in enhancing protection against virulent DEV in waterfowl.