| virulence of infectious laryngotracheitis viruses: comparison of modified-live vaccine viruses and north carolina field isolates. | virulence of six modified-live (ml) infectious laryngotracheitis (ilt) vaccine viruses was compared with that of 11 field isolates (indistinguishable from vaccine viruses by dna restriction endonuclease analyses) by intratracheal exposure of 4-week-old, specific-pathogen-free chickens. virulence of ilt viruses was based on an intratracheal pathogenicity index, mortality, and tracheal lesions. intratracheal pathogenicity indices for ml vaccine viruses ranged from 0.0 to 0.14, while those for fiel ... | 1990 | 2157386 |
| restriction endonuclease analysis of infectious laryngotracheitis viruses: comparison of modified-live vaccine viruses and north carolina field isolates. | six modified-live (ml) infectious laryngotracheitis (ilt) vaccine viruses, three reference strains, and 18 field isolates were compared by restriction endonuclease analysis of their dna. viral dna digestion patterns were established for vaccine viruses using restriction endonucleases psti, bamhi, kpni, and hindiii. using these enzymes, five of six ml vaccine viruses had identical restriction endonuclease cleavage patterns. vaccine viruses had distinct patterns compared with ilt virus reference s ... | 1989 | 2546530 |