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

Thumbnail Image
Open Access Location
Journal Title
Journal ISSN
Volume Title
Massey University
The Author
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 vaccination history. 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 fomites. 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.
Canine parvovirus, Dog diseases, Infectious diseases in dogs, Molecular epidemiology, Research Subject Categories::VETERINARY MEDICINE::Veterinary epidemiology