Differentiation of a porcine reproductive and respiratory syndrome virus vaccine strain from North American field strains by restriction fragment length polymorphism analysis of ORF 5

Virology Swine Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, Ames, IA 50010, USA. The suitability of restriction fragment length polymorphism (RFLP) analysis for differentiating a porcine reproductive and respiratory syndrome virus (PRRSV) vaccine strain from other North American field strains was investigated. Open reading frame 5 nucleotide sequence data of the vaccine virus, its parent strain VR-2332, and 22 other strains of PRRSV included in this study indicated that 3 restriction enzyme gel patterns characterize the vaccine virus and the parent strain genotype. The combined 3 RFLP patterns differentiate the vaccine and parent virus from other PRRSV strains. This test will be a valuable tool in epidemiologic studies and will be useful in identifying individual strains in cases of multistrain PRRSV infections.