title: Aerosol vaccination against Newcastle disease: factors affecting the serological response in chickens.
abstract: The effects of vaccine diluent and virus concentration on the immune response following aerosol vaccination against Newcastle Disease (ND) were studied. Four diluents (saline, tap water, distilled water and 2% casitone in distilled water) were used with various concentrations of LaSota strain virus. At low virus concentrations 2% casitone produced a higher HI antibody response than the other diluents. However, when the virus was administered in concentrations exceeding 7.4 +/- 0.4 logioEID50/m3, the recommended field dosage, virus suspensions in 2% casitone, distilled water and non-chlorinated tap water produced similar responses. The effect of virus concentration on the immune response was studied in 12- to 14-week-old chickens with or without residual immunity. Tenfold dilutions of ND virus of the LaSota strain were applied intratracheally or by aerosol and haemagglutination inhibition titres measured 2 and 4 weeks later. The dose producing an antibody response in 50% of the chickens was calculated both after intratracheal application and after aerosol vaccination. After intratracheal application doses of 0.9 log(10) EID50 and 1.8 log(10)EID50 were required to obtain a 50% response in specific pathogen free chickens and chickens with residual immunity respectively. When the virus was applied by aerosol 5.0 and 6.0 to 7.0 log(10)EID50/m3 were required to produce a 50% response in chickens without and with residual immunity, respectively.
authors.affiliation: Poultry Department, Central Veterinary Institute, Doom, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Yadin