MDV genome copy number in blood cells and feather tips of chickens. The rRB-1B EGFP22 or rRB-1B virus (1500 pfu) was inoculated intramuscularly in 1 week-old White Leghorn B13/B13 chickens (Experiment 2). Wing vein blood and axillary tract feathers were collected at different times post-infection. For all samples, DNA was extracted and examined for ICP4 and iNos by qPCR. A. % of ICP4-positive chickens after blood examination by qPCR over time. B. Viral loads (MDV genome copy number per million cells) in blood per chicken during the course of infection, with means curves for ICP4-positive birds. C. % of ICP4-positive chickens after feather tips examination by qPCR over time. D. Mean ± SEM viral loads in feather tips per group over time.