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. 2015 Aug 12;5:13038. doi: 10.1038/srep13038

Table 1. Pathogenicity of wild-type and HN-mutated viruses in SPF embryonated chicken eggs and chickens.

Virus Inline graphic Inline graphic IVPI§
rG7- wt 44 1.7 2.4
rG7- P93A 56 1.56 0.76
rG7- L94A 60 1.18 0.58

Inline graphicMean death time (MDT) pathotype definition: virulent strains, <60 h; moderately virulent strains, 60 to 90 h; avirulent strains, >90 h.

Inline graphicIntracerebral pathogenicity index (ICPI) is the criterion to classify the virulence of NDV isolates as recommended by the OIE. Pathotype definition: virulent strains, 1.5 to 2.0; moderately virulent strains, 0.7 to 1.5; avirulent strains, 0.0 to 0.7.

§Intravenous pathogenicity index (IVPI): velogenic strains yield values greater than 2.0, while avirulent strains approach 0.0.