Objectives: Canine parvovirus 2 (CPV-2) is a well-recognized cause of acute haemorrhagic enteritis in dogs worldwide. The antigenic differences between CPV subtypes are a consequence of amino-acid substitutions in several loci in the viral capsid protein VP2. These changes are thought to be associated with the antigenicity, host range and pathogenicity of the virus. The aim of the current study was to identify which CPV-2 subtypes currently circulate among dogs in New Zealand, and to investigate the evolutionary patterns of contemporary field CPV-2 viruses.
Methods: Faecal samples were collected from 79 dogs with suspected CPV-2 infection over the period of 13 months, and tested for the presence of CPV-2 DNA by PCR. The amplicons were sequenced and assigned to specific CPV-2 subtypes. In addition to the contemporary survey samples, 3 vaccine strains of CPV-2 and 9 archival CPV-2 isolates were included in the study. In addition, selected CPV-2 sequences with good quality sequence data were used to investigate the genetic structure of CPV-2 within New Zealand, as well as in the context of the worldwide radiation of CPV-2.
Results: Of 70 CPV-2 positive samples, 69 were subtyped as CPV-2a and one as CPV-2. A majority of CPV-2 positive samples were collected from not-fully vaccinated puppies ≤ 6 months of age, underscoring the importance of puppy vaccination for prevention of CPV-2 gastroenteritis. The haplotype network produced from New Zealand CPV-2 sequences showed little or no structure when assessed based on location, vaccination status or age of the animals sampled. International haplotype network indicated that, unlike CPV-2 from other countries, the population of CPV-2 in New Zealand appeared to be monophyletic. Hence, our data suggest that the on-going introduction of CPV-2 from other countries is not a common occurrence in New Zealand [1].