In order to study the importance of an intact thymidine kinase (TK) gene for the vaccine strain of a southern African capripoxvirus, namely, lumpy skin disease virus (LSDV) (type SA-Neethling), a TK disruption recombinant was generated expressing the Escherichia coli beta-galactosidase (lacZ) reporter gene. A comparative growth study of the recombinant and wild-type (wt) LSDV in TK-positive primary and secondary cells and TK-negative secondary cells was performed. It was found that although recombinant and wt virus both grew in TK-positive cells without selection, the recombinant was unable to grow in TK-negative cells (with or without selection), indicating that TK activity is important, if not essential, for normal growth of LSDV.