A study of Newcastle disease vaccine virus in sprays and aerosols.

The administration of two commercial Newcastle disease (ND) vaccines to chickens by aerosol was studied. The size distribution of non-evaporating droplets, produced by different aerosol generators, was measured. Using one of the generators - the Atomist - the size distribution of particles evaporating to equilibrium was determined. The sedimentation of the dry particles was judged by repeating the measurement after 10 and 30 min. This was done with distilled water, tap water, saline, and 1% and 2% solutions of Casitone, with and without vaccine. The stability of the vaccine virus at 20 degrees C in an aerosol of distilled water was minimal at high relative humidities. Measurement of viral stability in aerosols of different diluents produced with the Atomist in small pens showed an initial loss of infectivity of between 1 and 3 log(10) median embryo infectious doses (EID50). Further loss of infectivity was between 0.2 and 3.4 log(10) EID50/ hour. Distilled water was the optimal diluent for these commercial ND vaccines.