Based on the severity of pathogenicity, it is classified into four pathotypes as follows:
- Non-pathogenic or avirulent: does not cause any disease, such as the non-pathogenic strain of the V4 virus of genotype 1
- Lentogenic: low virulence, low mortality, loss of egg-like production and Lasota virus and B4 of genotype 2.
- Mesogenic: moderate severity, mortality up to 50%, reduction in egg production, high severity vulogenic, such as R2B virus.
- Velogenic: severe disease with high mortality
velogenic strains are divided into visceral velogenic (visceral organ orientation) and neurotropic (nervous orientation) strains in terms of tissue orientation.
such as the Newcastle G7 virus
Strains with intracerebral pathogenicity index (ICPI) ≥ 0.7 are defined as pathogenic strains according to the standards of the World Organization for Animal Health (OIE).
Velogenic strains cause embryo death in less than 60 hours, lentogenic NDV between 60 and 90 hours and lentogenic over 90 hours respectively.