Effect of preventing clinical Marek's disease (MD) was compared among frozen vaccine prepared from the low virulent C2 strain originated from MD herpes virus (MDHV) developed by the Osaka University Microbiological Disease Laboratory, frozen and freezedried vaccines prepared from the Ol strain of HV of turkey (HVT), and frozen vaccine tentatively prepared from HVT originated from sonie overseas laboratory.
Commercial White Leghorn chicks were used. When examined by the indirect fluorescent antibody technique, they had an anti-MDHV FA titer of 1: 1590 and an anti-HVT FA titer or 1: 470. They were inoculated intraperitoneally with vaccine at one day of age and challenged by the same route at 3 weeks of age. Chicks inoculated with the same vaccine were held in the same house separately from chicks inoculated with any other vaccine. Results were judged histopathologically in all the birds at about 20 weeks of age. In conclusion, there were no differences in the effect of prevention among the four vaccines. Besides, it was confirmed that a freeze-dried vaccine prepared from cell-free HVT showed a satisfactory effect even when inoculated into chicks possessing a ratherhigh level of maternal antibody.
