Application of the turkey herpesvirus vaccine by the aerogenic route for the prevention of Marek's disease.

Recently in laboratory and field trials, birds were vaccinated with cell-free HVT vaccine by aerosol spray. In laboratory trials, birds vaccinated by aerosol spray were as well protected against challenge with virulent MD (GA isolate) as those vaccinated by subcutaneous inoculation. Birds were vaccinated with a sprayer (Spraying Systems Company, Wheaton, Illinois) which emits a particle size in which 90% are less than microns. The chicks were sprayed with 1,000 to 10,000 PFU per bird dose and remained in contact with the aerosol for 30-60 min. Turkey herpesvirus was isolated from the blood or kidney of these birds as early as 7 to 10 days postvaccination. In field trials approximately 300,000 birds have been vaccinated by aerosol spray with between 2,000 to 5, 000 PFU of cell-free HVT vaccine per chick. Chicks were sprayed while they were in the trays of the hatchers which still contained the dust and down which remained after hatching. Prior to spraying, the incoming and outgoing aid ducts were closed. The chicks were sprayed for 12-15 min with 250-300 ml of diluent, and after completion of spraying the chicks remained in contact with tha aerosol for an additional 5 to 8 min. In the birds vaccinated by aerosol spray the incidence of MD in the processing plant varied from 0.0% to 23.4%, while the incidence of MD in birds vaccinated by subcutaneous inoculation varied from 0.02 to 23.9%. Overall the incidence of MD in birds vaccinated by aerosol spray was essentially the same as those vaccinated by subcutaneous inoculation.