Differentiation of wild- and vaccine-type canine parvoviruses by PCR and restriction-enzyme analysis

The polymerase-chain reaction (PCR) and restriction-fragment-length-polymorphism (RFLP) analysis were used to differentiate the wild- and vaccine-type of canine parvovirus (CPV) in Japan. The entire coding region of the CPV genome was enzymatically amplified, and the PCR products of three wild strains and four vaccine strains were analysed using RFLP assay. Then, two polymorphic regions in the VP1/VP2 gene were selected to generate strain-specific RFLP patterns. By using four restriction enzymes, wild and vaccine strains were clearly differentiated; only two vaccine strains, probably of the same origin, were indistinguishable from each other. The wild strains retained strain-specific RFLP patterns throughout in vitro passage, and there was no diversity of RFLP patterns among the different lots of vaccine strains. A total of 21 recent field samples were tested, showing RFLP patterns identical to those of a wild strain isolated in 1991. These results suggest that the PCR-RFLP analysis is a practical and reliable method of differentiating wild- and vaccine-type CPVs.