Effect of sampling site on the diagnosis of canine parvovirus infection in dogs using polymerase chain reaction

Molecular survey of canine parvovirus type 2: the emergence of subtype 2c in New Zealand

AIMS

To determine the genetic makeup of carnivore parvoviruses currently circulating in New Zealand; to investigate their evolutionary patterns; and to compare these viruses with those detected during the previous New Zealand-based survey (2009-2010).

METHODS

Faecal samples from dogs (n = 40) with a clinical diagnosis of parvovirus enteritis were voluntarily submitted by veterinarians from throughout New Zealand. In addition, one sample was collected from a cat with comparable clinical presentation. The samples were used for DNA extraction and PCR amplification of viral protein 2 (VP2) of canine parvovirus type 2 (CPV-2). All samples produced amplicons of the expected sizes, which were then sequenced. The viruses were subtyped based on the presence of specific amino acids at defined locations. In addition, VP2 sequences were analysed using phylogeny and molecular network analysis.

RESULTS

The majority (30/40; 75%) of CPV-2-infected dogs were younger than 6 months and 8/40 (20%) were aged between 9 months and 1 year. Most (39/41; 95%) parvoviruses were subtyped as CPV-2c, and one as the original CPV-2. The faecal sample from a cat was positive for feline panleukopenia virus. The majority (37/39; 95%) of New Zealand CPV-2c viruses were monophyletic. The remaining two New Zealand CPV-2c viruses clustered with Chinese and Sri Lankan CPV-2c viruses, separately from the main New Zealand clade.

CONCLUSIONS

There has been an apparent replacement of the CPV-2a viruses with CPV-2c viruses in New Zealand between 2011 and 2019. The source of the current CPV-2c viruses remains undetermined. The monophyletic nature of the majority of viruses detected most likely reflects a country-wide spread of the most successful genotype. However, an occasional introduction of CPV-2 from overseas cannot be excluded.

CLINICAL RELEVANCE

Current vaccines appear to be protective against disease caused by the CPV-2c viruses currently circulating in New Zealand. Vaccination and protection from environmental sources of CPV-2 until the development of vaccine-induced immunity remains the cornerstone of protection in young dogs against parvovirus enteritis. Ongoing monitoring of the genetic changes in CPV-2 is important, as it would allow early detection of variants that may be more likely to escape vaccine-induced immunity.

Integrative Analysis of Dog Serum-Derived CircRNA Expression and Disease Severity, Inflammatory and Cardiac Damage Biomarkers Related to Canine Parvoviral Enteritis

BACKGROUND

The tissue- and developmental stage-specific expression of circular RNAs (circRNAs) makes them promising disease biomarkers. CircRNAs play a crucial role in regulating inflammatory responses; however, their function in canine parvovirus (CPV) infection remains largely unexplored.

HYPOTHESIS

We hypothesized that circRNAs serve as biomarkers for disease severity, inflammation and organ damage in dogs with CPV.

MATERIALS AND METHODS

The study included six dogs with mild CPV, six with severe CPV and six healthy controls. Haematological and biochemical parameters were analysed from blood samples. CircRNA profiling in serum samples was conducted through high-throughput sequencing, followed by bioinformatic analysis to identify potential circRNA biomarkers. Associations between circRNAs and haematological/biochemical markers were examined.

RESULTS

The severe group exhibited significantly reduced leukocyte counts and elevated C-reactive protein (CRP) levels (p < 0.05). The mild group demonstrated higher levels of tumour necrosis factor-alpha (TNF-α), cardiac troponin I (cTnI) and creatine kinase myocardial band (CK-MB) (p < 0.05). Thus, the severe group experienced heightened inflammation, whereas the mild group demonstrated increased cardiac damage. Dogs with CPV expressed certain circRNAs differently (upregulated and downregulated), as revealed by gene ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analyses. Eighteen cicRNAs were identified as potential biomarkers. Bioinformatic and correlation analysis revealed that cfa_circ_6789, cfa_circ_6793, cfa_circ_6785, cfa_circ_6798, cfa_circ_6791, cfa_circ_6794 and cfa_circ_3119 could serve as biomarkers of inflammation and disease severity. Conversely, cfa_circ_3114, cfa_circ_3118, cfa_circ_3117, cfa_circ_3113, cfa_circ_3119, cfa_circ_1571, cfa_circ_6786 and cfa_circ_6794 were linked to cardiac damage.

CONCLUSIONS AND CLINICAL RELEVANCE

The identified circRNAs were actively involved in different stages of CPV infection and exhibited strong associations with disease onset and progression. They may play a key role in modulating infection pathogenesis while serving as potential biomarkers for inflammation and cardiac damage. This study is the first to investigate the role of circRNAs in CPV infection, providing novel insights into their diagnostic and prognostic potential.

Persistence of DNA from canine parvovirus modified-live virus in canine tissues

Canine parvovirus (CPV-2) modified-live virus vaccine strain can replicate in lymphoid tissues and intestinal mucosa after administration, being shed through canine faeces. Detection of vaccine strains has been reported in the bloodstream and faeces, potentially interfering with molecular diagnostic tests. The persistence of these strains in canine tissues has not yet been described. With this aim, canine tissues were tested during a molecular survey to screen for the presence of canine enteric viruses. Tissue samples from 165 dead dogs were tested by a conventional PCR assay. Positive samples and five commercial vaccines were subjected to sequence analysis. Vaccinal strains were detected and virus load was measured by using a set of real-time PCR assays using minor-groove binder (MGB) probes. Seventy-five dogs (45.4%) tested positive for CPV-2. Strains from 70 dogs were characterised as field variants. The presence of CPV sequences of vaccine origin was observed in the spleen, intestine, and mesenteric lymph nodes of five young dogs. Vaccinal strains were detected from 12 to 24 days after the last vaccine administration. Viral loads comprised between 6.3 × 10² and 9.95 × 10⁴ DNA copies/10 µl of template. This study confirms that CPV vaccinal strains can be detected in canine tissues after vaccination, so post-mortem diagnosis of CPV infection needs further molecular analyses to assess the viral type (vaccine or field strains). The present study updates the current information on the persistence of CPV vaccine strains in canine tissues and their possible interference with molecular assays.