IN OVO VACCINATION OF CHICKEN EMBRYOS WITH EXPERIMENTAL NEWCASTLE-DISEASE AND AVIAN INFLUENZA OIL-EMULSION VACCINES

Inactivated oil-emulsion (OE) Newcastle disease (ND) and avian influen za (AI) vaccines were injected into 18-day-old white rock (WR) and whi te leghorn (WL) chicken embryos to evaluate their immunologic efficacy and their effects on hatchability. Embryonating eggs were inoculated at 1.5 inches depth with various vaccine volumes and antigen concentra tions. Serum hemagglutination-inhibition (HI) titers were first detect ed in chickens at 2 wk posthatch. Protection against morbidity and mor tality was demonstrated in all of 10 chickens vaccinated as embryos an d challenged with viscerotropic velogenic ND virus at 53 days of age a nd also in all of eight in ovo-vaccinated chickens challenged with hig hly pathogenic AI virus at 34 days of age. ALL of five unvaccinated co ntrol chickens for each respective ND-and AT-vaccinated group died. In pooled groups from successive hatches, the hatchability of WR or WL e mbryos injected with 100 mu l of vaccine was not significantly differe nt (P > 0.05) from unvaccinated hatchmate controls when needle gauges of 22, 20, and 18 were used. Seroconversion rates of chickens vaccinat ed as embryos ranged from 27% to 100% with ND vaccination and 85% to 1 00% for AI vaccination. For ND, geometric mean HI titers of chickens p er vaccine group ranged from 11 to 733, and in pooled groups, the rang e was 49 ro 531. Titers for AI vaccine groups ranged from 156 to 1178. This study demonstrated that acceptable hatchability, seroconversion rates, and protective immunity can be attained with in ovo inoculation of ND or AT OE vaccines if the vaccines are prepared with sufficient antigen and administered properly.