Keywords: NDV; Newcastle Disease Virus; rNDV; recombinant NDV; FFA; Fluorescent Focus Assay; VCGM; Vero Cell Growth Medium; DMEM; Dulbeco's Modified Eagle Medium; FBS; Fetal Bovine Serum; DPBS; Dulbeco's Phosphate Buffered Saline; PFU; Plaque Forming Unit; FFU;