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

Abstract

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 × 10 2 and 9.95 × 10 4 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. Supplementary Information The online version contains supplementary material available at 10.1007/s11259-022-10008-7.

Molecular epidemiology of canine parvovirus type 2 in Sicily, southern Italy: A geographical island, an epidemiological continuum

“…Within the CPV-2b variant, strain 2019PA26796 showed the highest nucleotide identity (99.89%) with CPV-2b strains previously detected in Sicily in 2018 (accession number MT981027 [ 33 ]; and in 2020 (ON479068 [ 32 ]; strain 2019RG11304 with CPV-2b strains (99.94%) detected in Apulia (another region in southern Italy) in 2013 (MH491875; [ 12 ]) and in Emilia-Romagna (north-eastern Italy) in 2016 (MK348102; [ 13 ]); strain 2022PA15678idMeF showed the highest identities with CPV-2b strains detected on January 2022 in Sicily (100%; ON677437; [ 15 ]) and in July 2021 in Hungary (99.94%; ON733252; [ 35 ]). Although these latter strains, based on the VP2-426 residue, have been typed as CPV-2b, according to the phylogeny and the analysis of other aa residues, they could be considered as Asian CPV-2c likely revertant strains, showing how genotyping based exclusively on residue 426 is reductive.…”

“…Notably, vaccine-derived CPV-2 strains were detected in 1–3 samples per year, ranging between 1 and 9% of the positive samples. The occasional occurrence of vaccinal CPV-2 strains, as already observed [ 32 ], underlines the need to molecularly characterize the identified viruses, in order to discriminate between field and vaccinal strains since PCR-positive results are not necessarily indicative of an active infection by a field strain.…”

“…According to sequence motifs identified in a previous study [ 32 ], all eight sequences classified as original CPV-2 type were considered as vaccinal strains. Sequences typed as CPV-2a, CPV-2b, or CPV-2c according to the amino acid residue discriminating the CPV-2 variants (VP2-426), were further characterized and grouped according to their amino acid sequences.…”

Use of rapid immunochromatographic tests and PCR for the detection of vaccine viruses (CPV, CDV CAV) in faeces and conjunctival sac swabs of vaccinated dogs

“…In contrast, vaccine parvovirus genetic material can be detected by PCR in canine faeces and tissues up to 28 days after the vaccination (13,24).…”