Use of marker vaccines in IBR eradication programs is widely accepted since it allows for protection of the animals against the disease while adding the possibility of differentiating vaccinated from infected animals.The aim of the present study was the development and evaluation of safety and efficacy of a glycoprotein E-deleted ( gE - ) BoHV-1 marker vaccine strain ( BoHV-1gEgal ) generated by homologous recombination , replacing the viral gE gene with the - galactosidase ( gal ) gene .