Abstract
Porcine circovirus type 2 (PCV2) is a globally spread pathogen controlled with generally highly efficacious vaccination protocols. In order to compare PCV2 detection profiles in farms with different vaccination statuses, serum (359) and fecal pools (351) and oral fluids (209) from four farms that do not vaccinate against PCV2 (NON-VAC) and from 22 farms that do vaccinate (VAC) were tested with quantitative real-time PCR. Additionally, nucleotide sequences of ORF2 of the virus were obtained from selected samples. Three genotypes, PCV2a, PCV2b, and PCV2d, were detected. Significant differences (p < 0.05) in PCV2 prevalence and quantities between the VAC and NON-VAC farms were evident. In five VAC farms, no viremia or shedding in feces was detected. On the other hand, in four VAC farms, the results were very similar to those from NON-VAC farms. No significant difference in PCV2 prevalence in oral fluids was observed between VAC and NON-VAC farms. An examination of viremia can be recommended for the detection of vaccination efficacy issues. The median of the PCV2 viral loads >6.0 log10 copies/mL in pooled sera from the vaccinated population should be considered a very strong indication that the vaccination protocol needs revision.
Highlights
Porcine circovirus type 2 (PCV2) is a member of the family Circoviridae, genus Circovirus, which contains small, non-enveloped viruses with a single-stranded circular DNA genome about 1.7–2.0 kb in size [1]
No significant difference in PCV2 prevalence in oral fluids was observed between VAC and NON-VAC
Farms), clinical signs resembling PCV2-associated diseases (PCVD) were observed in some pigs of different ages, but a proper laboratory investigation was not performed to confirm the cause of the disease
Summary
Porcine circovirus type 2 (PCV2) is a member of the family Circoviridae, genus Circovirus, which contains small, non-enveloped viruses with a single-stranded circular DNA genome about 1.7–2.0 kb in size [1]. It is a primary causative agent of PCV2-associated diseases (PCVD), which include systemic illness, enteritis, pneumonia, and reproductive failure [2]. Porcine circovirus type 2 causes subclinical disease without specific clinical signs, which is the most common PCV2 manifestation [2]. Porcine circovirus type 2 can be classified into several genotypes or clusters [5]. PCV2a, PCV2b, and PCV2d are widely spread, PCV2b and PCV2d are the most commonly found in diseased pigs nowadays [6,7]
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