Protection against hemorrhagic enteritis and Newcastle disease in turkeys by embryo vaccination with monovalent and bivalent vaccines.

The feasibility of embryo vaccination against Hemorrhagic enteritis (HE) and Newcastle disease (ND) in specific-pathogen-free turkey embryos was studied. Turkey eggs were injected with marble spleen disease virus (MSDV) at embryonation day (ED) 24, and tissues of poults hatching from virus-injected eggs were examined for MSDV. The virus was detected in spleen, intestine, liver, and bursa between 4 to 10 days postinoculation (PI). The peak titer of MSDV was present in the spleen at 6 days PI. Poults hatching from eggs injected with MSDV produced antibodies to the virus and resisted a challenge with virulent hemorrhagic enteritis virus (HEV) at 4 weeks of age. The B1 strain of NDV (NDV-B1) injected in turkey eggs at ED 24 killed the embryos. NDV-B1 modified by treatment with ethylmethane sulfonate (NDV-B1-EMS) was not lethal for turkey embryos. Poults hatching from eggs injected at ED 24 with NDV-B1-EMS developed antibodies to NDV and were protected from challenge exposure with virulent NDV at 4 weeks of age. Poults from eggs inoculated at 24 ED with a bivalent vaccine containing MSDV and NDV-B1-EMS developed antibodies to both viruses and were resistant to challenge with both virulent viruses. The study showed that SPF turkeys may be immunized by in ovo injection of live viral vaccines.