High levels of vTR are dispensable for MDV cytolytic replication in vivo. Total DNA isolated from whole blood samples taken at days 4, 7, 11, 14, 21, 28, 35 and 42 p.i. from chickens infected with vPchTR+/+, vPvTR+/+ or the parental vRB-1B were used for qPCR analysis of the viral ICP4 gene and a host gene (iNOS). Mean viral loads are given as copies of ICP4 per 1 × 106 copies of chicken iNOS. No statistically significant differences in viremia levels were observed between groups infected with vPchTR+/+, vPvTR+/+ or vRB-1B. Graphs represented the means of 13 chickens per group and standard deviations are given (error bars).