A study of Newcastle disease vaccine virus in sprays and aerosols

Abstract

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.

Aerosol vaccination against newcastle disease: Virus inhalation and retention during vaccination

“…These differences are probably due to loss of virus by physical fallout and inactivation (Yadin and Orthel, 1978). The amount of virus per inhaled litre of air was 1.0 to 3.4 logs below the level expected from the titres of the virus suspensions (Tables 2 and 3).…”

“…A sample of each vaccine suspension was submitted for virus titration. Vaccination In each experiment 100 ml of virus suspension was nebulised in 20 seconds using the "Atomist" (Lowell, Michigan, U.S.A.) as described before (Yadin and Orthel, 1978) in a rectangular pen of 39m 3 volume without windows. During aerosol generation and for a period of 30 min thereafter ventilators were stopped and the air inlet and outlet were closed with plastic sheets.…”

“…Tenfold serial dilutions of the vaccine virus and impinger fluids were prepared and treated as described before (Yadin and Orthel, 1978). Titres were calculated according to Reed and Muench (1938) and expressed as logio of the median embryo infective dose (EID 50 ).…”

Spray drying of an attenuated live Newcastle disease vaccine virus intended for respiratory mass vaccination of poultry

“…These particles are well suited for primary respiratory vaccination of poultry where deposition in the lower airways should be avoided to prevent post-vaccination reactions in the more vulnerable lungs [3][4][5]. To obtain this, vaccination of 1-day-old chickens should be performed with particles larger than 20 m, as determined in a previous study [37].…”

“…A first problem is the broad droplet size distribution generated by the nebulizers currently used for liquid spray and aerosol vaccination: the presence of small, inhalable droplets in a coarse spray for primary vaccination often results in post-vaccination reactions [3][4][5] and a large fraction of non-inhalable droplets generated by fine aerosol nebulizers (e.g., 10-1000 m [6]) reduces the efficiency of secondary vaccinations. Furthermore, the efficiency of vaccines administered by spray or aerosol might be jeopardized due to the use of tap water for reconstitution (often containing virucidal agents, such as chlorines) [7], by large shear forces which are applied to the liquid in order to transform it into droplets [8] and most importantly, due to inactivation of the vaccine virus by evaporation of droplets after generation [3,5,9].…”