Field Experiences with Newcastle Vector Vaccines in the US

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Abstract

Newcastle Disease (ND) is caused by lentogenic viruses in the U.S. This fortunate fact has historically allowed U.S. poultry producers to successfully control this respiratory disease using inexpensive and mildly reactive B1B1 strain live NDV vaccines applied in combination with modified live IBV vaccines. Thus the recent introduction of HVT vector vaccines for control of NDV represented a unique challenge for U.S. poultry producers: how to best economically evaluate a ND vector vaccine in a poultry production system with inherently mild NDV disease challenge?

For one large U.S. broiler producer the answer to this question was to conduct simultaneous large scale field trials in three broiler complexes located in two different geographic areas. Live B1B1 NDV (control) and HVT vector NDV (trial) vaccines were exclusively used during alternate placement weeks continuously for over six months to provide a contemporary side by side comparison of performance results inclusive of both winter and summer growing conditions. Identical modified live Mass/Ark IBV vaccines were administered to both control and trial placement groups to keep NDV vaccine the only variable between the groups.

Two trial complexes were located in a poultry growing area considered to have high overall disease challenge (Delmarva Peninsula) and one trial complex was located in North Carolina where disease challenge is thought to be low. Trial complexes on Delmarva included both 6.50 lb (49d) and 8.25 lb (60d) bird size growing programs while the NC complex included 8.75 lb (63d) birds only.

Performance parameters compared in the trial included two week mortality, growing mortality, weight gain per day, adjusted feed conversion and condemnations. Results were calculated and evaluated weekly. Differences between treatment groups and seasonal trends were observed in some trial complexes. At the conclusion of the trials HVT vector NDV vaccination programs were adopted in two of the three trial complexes.

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