Detecting Marek's Disease Herpesvirus: Evaluation of Biological Systems

Abstract

Systems were evaluated for isolating and identifying Marek's disease herpesvirus (MDHV) from purposely contaminated samples of poultry virus vaccines. The sensitivity and specificity of duck embryo fibroblasts (DEF) and chick kidney (CK) cell cultures for detecting MDHV were compared with the inoculation of embryonated eggs and day-old chicks. Duck embryo fibroblast cell cultures were more sensitive for detecting MDHV and less susceptible to the cytopathogenic effect (CPE) of vaccine viruses than either CK cell cultures or embryonated eggs. The inoculation of day-old chicks appeared less sensitive than DEF cell cultures when infection was determined by culture of kidneys or by use of a radial diffusion test for MDHV feather follicle antigen at 14 days postinoculation. At 21 days postinoculation, chicks appeared as sensitive as DEF cell cultures when infection was determined by kidney culture and more sensitive than cell cultures when the radial diffusion test was employed to determine infected birds. Inoculation of chicks was the only satisfactory method for isolating MDHV from samples of avian pox virus vaccines. Fluorescent-antibody (FA) staining confirmed the identity of MDHV isolates made in DEF cell cultures. The FA procedure was used to examine 28 samples of commercial virus vaccines for MDHV. This virus was not detected as a contaminant in any of the samples.