Laboratory tests for comparing live lentogenic newcastle disease vaccines.

Eighteen Newcastle disease virus vaccines (B1, LaSota and AG68L) were evaluated using various test methods. The main parameters considered were potency (expressed as an end point titre), respiratory stress effect and immunisation in the presence of maternally derived antibody. Results using vaccines of different origins were compared and replicate testing used to estimate the significance of the results. It was concluded that there were differences between vaccines in immunising capacity, potency levels and stress effects. LaSota vaccines were found to be more varied, more heterogeneous and generally more immunogenic than the B1 vaccines, however, the AG68L vaccines were found to be more immunogenic than either the B1 or LaSota vaccines.