Canine parvovirus in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Veterinary Studies in Virology at Massey University, Turitea, Palmerston North, New Zealand
Since the initial global emergence of canine parvovirus type 2 (CPV-2) in the early 1980s the
virus has continued to evolve in its new host. As a result, the original CVP-2 was replaced by
newly emerged subtypes designated CPV-2a and CPV-2b. Recently, a third antigenic subtype
CPV-2c has emerged in several countries. In New Zealand the evolution of CVP-2 has not
been monitored since its emergence in the early 1980s, largely because of the high efficacy of
the vaccines available on the market. This lack of monitoring of CPV-2 has left a dearth of
knowledge regarding the epidemiological features of CPV-2 in New Zealand. Hence, the aim
of this study was to determine what subtypes of CPV-2 circulate in New Zealand and to
investigate the phylogenetic relationships between CPV-2 from New Zealand and from other
parts of the world.
As part of this project, a virological survey was conducted across New Zealand. A total of 79
faecal samples were collected from dogs suspected to be infected with CPV-2, as judged by
submitting veterinarians. Of those, 70 tested positive for CPV-2 DNA. All but one of the
CPV-2 sequences were subtyped as CPV-2a. The remaining sequence was subtyped as CPV-
2, and most likely represented a vaccine strain of the virus. The majority (74.3%) of CPV-2
positive samples originated from dogs six months of age and younger, with 70% of samples
collected from dogs considered not fully vaccinated (unvaccinated dogs or those with only
single vaccination), a further 17% of samples originated from dogs with an unknown
Two separate phylogenetic analyses were performed. Seventy one CPV-2 positive sequences
originated from New Zealand (61 survey samples, six historic samples, two vaccine
sequences and one parvovirus sequence obtained from a cat) and the reference sequence were
trimmed to produce contiguous sequences of equal length. These 72 sequences were used to
investigate the genetic structure of CPV-2 within New Zealand. Haplotype network analyses
revealed that Cook-straight [i.e. Cook Strait] is not an effective geographical barrier to CVP-2 gene flow with
an equal distribution of genotypes in the North and South Islands. Translocation of the virus
between the islands is likely occurring by transportation of sub-clinically infected animals and
Additional CPV-2 VP2 sequences (n=95) originating from various countries were obtained
from the National Centre for Biotechnology Information (NCBI) database. The selection of 27
samples originating from New Zealand for which a full length contiguous sequence of VP-2
gene was available were aligned with sequences obtained from the NCBI database. The
resulting dataset of 123 CPV-2 sequences was used to assess the New Zealand CPV-2
sequences in the context of the worldwide radiation of CPV-2. Phylogenetic analyses of this
dataset revealed that New Zealand has a closed monophyletic population of CPV-2 sequences.
This suggests that CPV-2 is not being continuously introduced to New Zealand from
overseas, but has evolved following a limited number of introductions in the past.
Phylogenetic analysis also revealed that CPV-2 subtypes from around the world have
emerged independently of one another.
This work has contributed to our understanding of molecular epidemiology of CPV-2 in New
Zealand. The knowledge of predominant CPV-2 subtypes circulating in this country is
important for evidence driven recommendations with regard to CPV-2 vaccination.
Understanding of the genetic structure of the current CPV-2 circulating in New Zealand is
also crucial for timely recognition, detection and management of any novel antigenic subtypes
that may emerge in the future.