No evidence for a role of modified live virus vaccines in the emergence of canine parvovirus

In this study the early evolution and potential origins of canine parvovirus (CPV) were examined. We cloned and sequenced the VP2 capsid protein genes of three German CPV strains isolated in 1979-1980, as well as two feline panleukopenia virus (FPV) vaccine viruses that were previously shown to have some restriction enzyme cleavage sites in common with CPV. Other partial VP2 gene sequences were obtained by amplifying CPV DNA from paraffin-embedded tissues of dogs which were early parvovirus disease cases in Germany in 1978-1979. Sequences were analysed with respect to their evolutionary relationships to other CPV and FPV isolates. Those analyses did not support the hypothesis that CPV emerged as a variant of an FPV vaccine virus. Neither did they reveal ancestral sequences among the very early CPV isolates examined. Other possible sources for the origin of CPV are examined, including the involvement of viruses from wild carnivores.