A molecular survey and phylogenetic analysis of porcine circovirus type 3 using oral fluid, faeces and serum

Comparison of four clinical sample types for detection and investigation of PCV3 prevalence in the pig farrowing room

Porcine circovirus type 3 (PCV3) is a newly described circovirus that has been identified in pig populations across the globe. The virus is associated with multiple diseases including reproductive and systemic diseases. As effective vaccines are lacking, surveillance is crucial for PCV3 control, but there are currently, few side-by-side comparisons of the efficacy of different samples for the detection of PCV3. This study collected four sample types, including colostrum, udder skin wipes, placental umbilical cord blood, and processing fluid from 134 litters in a sow farm from July to September 2021 for PCV3 detection based on quantitative PCR tests. Udder skin wipes showed the highest detection rates (76.9%), while 71.6% of the processing fluid, 49.3% of the placental umbilical cord, and 29.1% of the colostrum samples were positive. Logistic regression analysis suggested that the detection rates of udder skin wipes and processing fluid were similar (odds ratio for processing fluid vs udder skin wipes was 0.76, 95% confidence interval (CI) 0.43-1.32), but the two tests were probably not identifying the same population as infected, as the agreement between the samples was only moderate (Gwet's AC1: 0.65). In this study, we were able to demonstrate that PCV3 was present in the farrowing room throughout the period from birth to weaning using udder skin wipes, although viral load decreased over time. The odds of PCV3 detection in colostrum from 2-parity sows was three times higher (95% CI 1.4-6.8) than that of primiparous sows, while the odds of PCV3 detection in sows with mummified fetuses was 2.7 times higher (95% CI 1.1-6.6) than sows with no mummified fetuses. In conclusion, these results indicate that udder skin wipes have high detection rates in infected animals over the whole period from birth to weaning and would thus be suitable samples for PCV3 surveillance in the farrowing rooms.

Revisiting Porcine Circovirus Infection: Recent Insights and Its Significance in the Piggery Sector

Porcine circovirus (PCV), a member of the Circoviridae family within the genus Circovirus, poses a significant economic risk to the global swine industry. PCV2, which has nine identified genotypes (a-i), has emerged as the predominant genotype worldwide, particularly PCV2d. PCV2 has been commonly found in both domestic pigs and wild boars, and sporadically in non-porcine animals. The virus spreads among swine populations through horizontal and vertical transmission routes. Despite the availability of commercial vaccines for controlling porcine circovirus infections and associated diseases, the continuous genotypic shifts from a to b, and subsequently from b to d, have maintained PCV2 as a significant pathogen with substantial economic implications. This review aims to provide an updated understanding of the biology, genetic variation, distribution, and preventive strategies concerning porcine circoviruses and their associated diseases in swine.

High Prevalence of Porcine Circovirus 3 in Hungarian Pig Herds: Results of a Systematic Sampling Protocol

Porcine circovirus type 3 (PCV3) is an emerging pathogen that has been reported worldwide in all ages of healthy and clinically ill pigs. The presence of this virus in Hungary has been confirmed in a commercial farm experiencing reproductive failures, but there were no data on the circulation of PCV3 in the country. Here we report the prevalence and the genetic diversity of PCV3 in Hungarian herds. To estimate the prevalence, 1855 serum samples, 176 oral fluid and 97 processing fluid samples were collected in a systematic, cross-sectional method from 20 large scale swineherds and tested by real-time qPCR. PCV3 was present in at least one type of diagnostic matrix in 19 out of the 20 (95%) pig farms. The highest detection rates were observed in the processing fluid samples (61%), but 41% of the oral fluid and 23% of the serum samples were positive. The virus was found in all age groups, and slightly more adult animals were infected than growing pigs, but the viral burden was lower amongst them. Phylogenetic analysis of nine complete genomes, obtained from either the sampled herds or organ samples of PCV3-positive carcasses, showed high nucleotide identity between the detected sequences, which all belonged to the PCV3a genotype. Our results indicate that PCV3 is widespread in Hungary, but in most cases, the virus seems to circulate subclinically, infecting all age groups and production phases without the presence of apparent clinical disease.

Phylogenetic analysis of porcine circovirus 3 circulating in Canadian pigs

Introduction

Porcine circovirus 3 (PCV3) has been detected in pigs worldwide and associated with several clinical signs.

Methods

To investigate the genetic diversity of PCV3 strains circulating in Canada, 44 PCV3 positive samples from Saskatchewan (2/44), Manitoba (2/44), Quebec (4/44), Alberta (11/44) and Ontario (25/44) submitted to diagnostic laboratories in Canada between 2019 and 2021 were sequenced and analyzed.

Results

Phylogenetic analysis of capsid genes showed that all of the 44 Canadian strains classified into PCV3a and segregated into seven lineages with common amino acid changes observed at A24V, R27K, N56D, T77S, Q98R, L150I (F) and R168K positions.

Conclusion

Future studies are required to determine whether the polymorphisms in capsid proteins, as revealed in this study, could be associated with differences in the pathogenicity or antigenicity of PCV3 strains. This is the first phylogenetic analysis of PCV3 strains among different provinces in Canada.

What do we know about porcine circovirus 3 (PCV3) diagnosis so far?: A review

Porcine circovirus 3 (PCV3) was first discovered in 2016, almost concomitantly by two groups of researchers in the United States. The novel case was reported in a group of sows with chronic reproductive problems with clinical presentation alike porcine dermatitis and nephropathy syndrome (PDNS), where metagenomic sequencing revealed a genetically divergent porcine circovirus designated PCV3. The discovery of PCV3 in a PDNS case, which used to be considered as part of PCVAD attributed to PCV2 (porcine circovirus 2), has garnered attention and effort in further research of the novel virus. Just when an infectious molecular DNA clone of PCV3 has been developed and successfully used in an in vivo pathogenicity study, yet another novel PCV strain surfaced, designated PCV4 (porcine circovirus 4). So far, PCV3 has been reported in domestic swine population globally at low to moderate prevalence, from almost all sample types including organ tissues, faecal, semen and colostrum samples. PCV3 has been associated with a myriad of clinical presentations, from PDNS to porcine respiratory disease complex (PRDC). This review paper summarizes the studies on PCV3 to date, with focus on diagnosis.