TABLE 1.
Pathogenicity of parental and chimeric viruses in embryonated eggs and in chicks
| Virus | MDT (h)a | ICPIb |
|---|---|---|
| rLaSota | 117 | 0.00 |
| rLaSota-VP1 | 144 | 0.00 |
| Modified rNDV | 108 | 0.00 |
| Modified rNDV-VP1 | 135 | 0.00 |
a
The mean embryo death time (MDT) is the mean time (h) for the minimum lethal dose of virus to kill all of the inoculated embryos. For pathotype definition, virulent strains had an MDT of <60 h, intermediately virulent strains had an MDT of 60 to 90 h, and avirulent strains had an MDT of >90 h.
b
Pathogenicity of NDV in 1-day-old SPF chicks was evaluated by the ICPI assay. For pathotype definition, virulent strains had an ICPI of 1.5 to 2.0, intermediately virulent strains had an ICPI of 0.7 to 1.5, and avirulent strains had an ICPI of 0.0 to 0.7.