[Marek's disease--characterization of the VUB-70 strain in vivo].

In the course of serial passaging of the strain of Marek's disease (MD) (VUB-70) in White Leghorns the author investigated the morbidity, mortality, development of the MD-specific changes, and the effect of sex on these indices, for the purpose of characterization of the biological properties of an isolated strain of MD in vivo. The incubation period lasted from 41 to 46 days p. inf. on the first day of life. Pullets showed greater sensitiveness towards infection not only through higher morbidity and mortality, but also due to a larger number of tumorous changes. In MD-positive animals the same proportion of macroscopic and microscopic changes was found. The average occurrence of Marek's disease amounted to 74.4 p. c. On the basis of the biological properties in vivo the VUB-70 strain was characterized as a medium pathogenic strain of the acute form of Marek's disease.