Inactivated oil-emulsion (OE) Newcastle disease (ND) and avian influenza (AI) vaccines were injected into 18-day-old white rock (WR) and white 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 concentrations. Serum hemagglutination-inhibition (HI) titers were first detected in chickens at 2 wk posthatch. Protection against morbidity and mortality was demonstrated in all of 10 chickens vaccinated as embryos and challenged with viscerotropic velogenic ND virus at 53 days of age and also in all of eight in ovo- vaccinated chickens challenged with highly pathogenic AI virus at 34 days of age. All of five unvaccinated control chickens for each respective ND- and AI-vaccinated group died. In pooled groups from successive hatches, the hatchability of WR or WL embryos injected with 100 microliters of vaccine was not significantly different (P > 0.05) from unvaccinated hatchmate controls when needle gauges of 22, 20, and 18 were used. Seroconversion rates of chickens vaccinated as embryos ranged from 27% to 100% with ND vaccination and 85% to 100% for AI vaccination. For ND, geometric mean HI titers of chickens per vaccine group ranged from 11 to 733, and in pooled groups, the range was 49 to 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 AI OE vaccines if the vaccines are prepared with sufficient antigen and administered properly.

Animals↗

PubMedDate not supplied

Molecular characterization of the hemagglutinin gene and oral immunization with a waterfowl-origin avian influenza virus.

Vaccination against highly pathogenic (HP) subtypes of avian influenza (AI) virus in poultry has been prohibited in the United States. Recently, policy has been changed to potentially allow use of inactivated vaccines in emergency programs to control HP H5 and H7 AI. Vaccination with inactivated virus against non-highly pathogenic AI viruses has been allowed in the U.S. turkey industry since 1979 (1) but requires expensive handling of individual birds for parenteral inoculation. Oral immunization would provide a less expensive method to protect commercial poultry from AI. Prime candidates for oral vaccines are waterfowl-origin (WFO) isolates, which have a tropism for the alimentary tract. One WFO isolate, A/mallard/Ohio/556/1987 (H5N9) (MOh87), was characterized by determining the complete nucleotide sequence of its hemagglutinin (HA) gene. The HA protein of this isolate possessed a deduced amino acid sequence nearly identical to the consensus amino acid sequence for all published H5 genes, indicating that it has potential as a broadly effective vaccine. Experimental results demonstrated measurable serum antibody responses to orally delivered live and inactivated preparations of MOh87. Oral vaccination also protected chickens from diverse, lethal H5 AI virus challenge strains and blocked cloacal shedding of challenge virus.

Administration, Oral↗