Prevalence and phylogenetic analysis of the current porcine circovirus 2 genotypes after implementation of widespread vaccination programmes in the USA

Abstract

To determine the prevalence of porcine circovirus 2 (PCV2) genotypes in the USA during 2010-2011, 5 years after widespread PCV2 vaccination, serum samples from clinically normal pigs that were PCV2 vaccinated (n51177), non-vaccinated (n5378) or of unknown vaccination status (n5120), and 100 lung samples from pigs diagnosed with PCV-associated disease (PCVAD) were tested. The presence of PCV2, PCV1, PCV1-2a and porcine parvovirus (PPV) DNA was determined by PCR. Determination of the PCV2 genotype was done by differential PCR and sequencing. The prevalence of PCV2a and PCV2b in serum samples was 7.7 % (129/1675) and 8.4 % (141/1675), respectively. PCV2a DNA was only detected in non-vaccinated pigs. For the 100 PCVAD pigs, the prevalence of PCV2a and PCV2b in lung tissues was 13.0 and 65.0 %, respectively. Partial PCV2 ORF2 sequences (9-563 nt) were obtained from 85 PCV2 DNA-positive samples (24 normal pigs and 61 PCVAD cases). Phylogenetic analysis revealed that 12.9 % (11/85) of the sequences belonged to the 2E clade and the PCV2a genotype and 87.1 % (74/85) belonged to the 1B clade and the PCV2b genotype. The alignment of putative PCV2 capsid amino acid sequences revealed possible recombination or mutation between PCV2a and PCV2b genotypes. Chimeric PCV1-2a was not detected in any of the samples and the prevalence rates of PCV1 and PPV were low. Our results suggest PCV2b is more prevalent than PCV2a in PCVAD cases and in vaccinated herds PCV2b circulation is common. The data generated in this study provide novel information on the distribution of PCV2 genotypes in vaccinated pig populations.

Association of concurrent porcine circovirus (PCV) 2a and 2b infection with PCV associated disease in vaccinated pigs

“…We found that the PCV2a and the PCV2b sequences were consistent with traditional PCV isolates similar to those previously reported in U.S. pigs Shen et al, 2012). Recombinations were not identified and the viral sequences were not different from those published previously indicating that the outbreak was not due to a novel PCV2 strain or the recently emerging mutant PCV2b Opriessnig et al, 2013).…”

“…The Fostera™ PCV vaccine (Zoetis) is an inactivated chimeric PCV1-2 vaccine. Even though currently PCV2b genotype is the predominant type infecting pigs worldwide (Gagnon et al, 2007;Dupont et al, 2008;Kim et al, 2011;Shen et al, 2012), all vaccines are based on the PCV2a genotype and have been shown to confer cross-protective immunity against PCV2b under experimental conditions (Fort et al, 2008;Opriessnig et al, 2009). An outbreak of PCVAD was observed in early finisher pigs in a PCV2 vaccinated, porcine reproductive and respiratory syndrome virus (PRRSV) positive, multisource wean-to-finish herd located in the United States.…”

Recognition of the Different Structural Forms of the Capsid Protein Determines the Outcome following Infection with Porcine Circovirus Type 2

“…PCV2 antigen in lung is associated with the onset of porcine respiratory disease complex (3,31). Further, Shen et al (38) showed that PCV2 DNA was more prevalent in the lung than in the serum of pigs with PCVAD. One interesting observation in this study was the presence of PCV2 antigen in the lung epithelium of the pigs in the Bac-CP group, even in the absence of viremia.…”

Complete Genome Sequence of a Novel Porcine Circovirus Type 2b Variant Present in Cases of Vaccine Failures in the United States

“…However, according to the new PCV2 genotype definition and nomenclature criteria (1, 7), all of these novel mutant PCV2 strains could be classified into genotype PCV2b, based on the phylogenetic analysis of the nucleotide sequence of ORF2 gene. Notably, in a previous large field investigation conducted in the United States during 2010 to 2011 in which 185 putative amino acid sequences of the PCV2 ORF2 were obtained, aligned, and compared, the novel mutant PCV2b sequence was not present (8).…”