Viral supernatant from passage 5 (CEL5), CEL10, CEL15, CEL20, CEL25, CEL30 and CEL35 were determined for titration by 50% tissue culture infective dose (TCID50) as described by Reed and Muench [1938]. Supernatant was diluted for 10 folds serial dilution and inoculated onto fresh CEL cells in 96 wells plate and monitored daily for CPE. Virus titre was calculated and expressed as TCID50/mL.