Field evaluation of Newcastle disease immunisation by concurrent inactivated oil-emulsion and live B1 vaccines

Protection of broilers against Newcastle disease by hyperimmunisation of the dams

A flock of broiler parents was hyperimmunised against Newcastle disease (ND) by subcutaneous injection of an experimental high-potency inactivated oil emulsion (IOE) vaccine in order to achieve high and long-lasting passive protection in broilers. During the egg production period mean log2 HI ND titre of the parents slowly decreased from 11.6 at 26 weeks of age to 10.0 at 53 weeks of age. Titres of day-old progeny paralleled those of their parents. Mean protection of broilers against mortality following challenge with Herts 33 virus at the ages of 1, 2, 3 and 4 weeks was 86%, 73%, 54% and 44%, respectively. As compared with the current Dutch situation, application of the high-potency IOE vaccine will significantly increase antibody titres in parent flocks and the level and duration of passive protection in broilers. It is concluded that passive ND protection of broilers by hyperimmunisation of the dams is realisable from an economic point of view and is suitable for low-risk areas.

Immunity to Newcastle disease in fowl of different breeds, primarily vaccinated with commercial inactivated oil-emulsion vaccines: a laboratory experiment

Fowl were primarily vaccinated with commercial inactivated oil emulsion (IOE) Newcastle disease (ND) vaccines and immunity was established by both determination of haemagglutination inhibiting (HI) antibodies and by challenge, over periods similar to the economic life span of the birds. The effect of level of maternal antibodies, route of vaccine administration, and vaccine dose on the vaccination results were studied. In one experiment, immunity provoked by vaccination with IOE vaccine was compared with that obtained by vaccination with live vaccines. Vaccination by the subcutaneous route induced a significantly stronger HI response than intramuscular vaccination. Also the vaccine dose per bird and the level of maternal antibodies influenced the vaccination results. In both brown layer and White Leghorn (WL) hens a strong immunity was induced up to at least 45 and 78 weeks of age respectively, by vaccination with IOE vaccine at 6 weeks of age. Also WL hens primarily vaccinated with IOE vaccine at 70 weeks of age, responded with high levels of HI antibodies, which persisted for at least 39 weeks. However, immunity in meat type fowl vaccinated at 6 weeks of age was poor. Following subcutaneous vaccination of one-day-old broilers with high maternal antibody titres with one dose of IOE vaccine per bird, immunity during the fattening period was at an insignificantly lower level than in birds vaccinated with live vaccine at 7 days of age. Twofold vaccination with IOE vaccine at one day old and 18 weeks of age of meat type fowl with high maternal antibody titres provoked a moderate immunity up to at least 55 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

The serological response of chickens to oil emulsion vaccines containing the V4 strain of Newcastle disease virus

Experiments were conducted with vaccines containing the V4 strain of Newcastle disease virus (NDV). Both living aqueous vaccines and vaccines consisting of virus incorporated oil emulsion were used. The calculated dose of virus contained in the oil emulsion vaccine was 10(8.7) 50% embryo infectious doses (EID50) per bird dose. Haemagglutinin inhibition (HI) antibody levels of 8 are presumed protective. One-day-old chicks with low levels of maternal antibody were vaccinated intraocularly with 10(6.3)EID50 ol live vaccine, and concurrently with oil emulsion vaccine. Presumed protective levels of antibody were present at two weeks post vaccination and were maintained for at least seven weeks longer. When adult birds 15 weeks old with no previous exposure to NDV were vaccinated intraocularly with 10(6.7)EID50 per bird, protective levels of antibody were produced within a week. Unvaccinated birds put in contact with the vaccinated birds produced similar antibody levels within 14 days. Revaccination with oil emulsion vaccine after antibody levels had fallen resulted in a rapid response with high levels of antibody. When antibody-free adult commercial birds with an unknown history of exposure to NDV were vaccinated intramuscularly with oil emulsion vaccine, high antibody levels were produced for at least 21 weeks. Concurrent intraocular inoculation with 10(7.0)EID50 live virus did not enhance the response. Natural infection of unvaccinated birds occurred during the experiment. This was detected by the presence of HI antibody levels of short duration. When antibody-free commercial birds were inoculated intramuscularly with oil emulsion vaccine containing 10(6.0), 10(7.0), or 10(8.0)EID50 per bird dose, 100% of birds inoculated with the highest dose produced presumed protective levels of antibody within two weeks, as compared with a 5-week delay when using the 10(7.0)EID50 per bird dose.