Isolation from Turkeys of a Cell-Associated Herpesvirus Antigenically Related to Marek's Disease Virus

SUMMARY Cytopathic herpesviruses ( hvt ) were isolated in chick kidney and duck embryo fibroblast cell cultures from blood and kidneys of turkeys from 3 flocks in Indiana and Georgia. In vitro characteristics of these isolates were similar and included highly cell-associated infectivity, syncytial-type cytopathology, type A intranuclear inclusion bodies, inhibition of plaque formation by 5-bromodeoxyuridine (5- budr ), and presence of herpesvirus-type particles. The hvt isolates were serologically identical but were distinguishable from other viruses previously isolated from turkeys. The virus was nonpathogenic for both turkeys and chickens through 8 weeks; however, recovery of virus and presence of precipitating antibody indicated that both hosts were susceptible to infection. The hvt could be differentiated from virulent and attenuated isolates of Marek's disease herpesvirus ( mdhv ), but results of agar gel precipitin, fluorescent antibody, and neutralization studies revealed a substantial antigenic relationship between hvt and mdhv .