The present disclosure relates methods and compositions useful for prevention of porcine reproductive and respiratory syndrome virus (PRRSv) in animals, including animals of the species Sus scrofa. The present teachings relate to swine wherein at least one allele of a CD163 gene has been inactivated, and to specific methods and nucleic acid sequences used in gene editing to inactivate the CD163 gene. Swine wherein both alleles of the CD163 gene are inactivated are resistant to porcine reproductive and respiratory syndrome virus (PRRSv). Elite lines comprising homozygous CD163 edited genes retain their superior properties.