Mixed treatment comparison meta-analysis of porcine circovirus type 2 (PCV2) vaccines used in piglets

A Chimeric Vaccine against Porcine Circovirus Type 2: Meta-Analysis of Comparative Clinical Trials

This meta-analysis compared the efficacy of a chimeric vaccine against porcine circovirus type 2 (PCV2) containing the genotypes PCV2a+b (Fostera® Gold PCV MH [FOS-G]), with commonly used vaccines being derived from genotype PCV2a, considering the following parameters: average daily gain (ADG), mortality and market classification as full value and cull. Data from seven hitherto unpublished comparative US field trials with FOS-G (two experimental challenges and five natural environmental studies) were provided by the manufacturer. A complementary literature review revealed a Korean study, which was considered separately in meta-analysis. Competitors were Circumvent® PCV-M (CV) and Ingelvac Circoflex® + Ingelvac Mycoflex® (IC + IM) in the US, and Porcilis® (POR) in Republic of Korea. Heterogeneity between experimental and environmental challenge studies in the US was not significant, justifying a combined analysis. Over the entire feeding period, ADG (11 comparisons), mortality (12 comparisons) and market classification were not significantly different between FOS-G and its competitor in the US setting. In the Korean study, however, ADG was higher in pigs vaccinated with FOS-G compared to POR, whereas mortality was not significantly different.

Maximizing value and minimizing waste in clinical trial research in swine: Selecting interventions to build an evidence base

Researchers conduct a trial to compare an intervention of interest to a comparison group. Initially, researchers should determine whether a trial is evaluating superiority, equivalence, or noninferiority. This decision will guide the choice of a placebo versus active comparison group. Interventions, as well as baseline management, should be comprehensively reported to allow replication or clinical application. It is necessary to build a body of evidence across multiple trials to apply evidence-based decision-making. To achieve this, at least one intervention in every trial should be an intervention that has been used in at least one previously published trial.

Revisiting Porcine Circovirus Disease Diagnostic Criteria in the Current Porcine Circovirus 2 Epidemiological Context

Current knowledge on porcine circovirus diseases (PCVD) caused by Porcine circovirus 2 (PCV-2) includes the subclinical infection (PCV-2-SI), systemic (PCV-2-SD) and reproductive (PCV-2-RD) diseases, and porcine dermatitis and nephropathy syndrome (PDNS). Criteria to establish the diagnosis of these conditions have not changed over the years; thus, the triad composed by clinical signs, lesions and viral detection in lesions are still the hallmark for PCV-2-SD and PCV-2-RD. In contrast, PCV-2-SI diagnosis is not usually performed since this condition is perceived to be controlled by default through vaccination. PDNS is diagnosed by gross and histopathological findings, and PCV-2 detection is not recognized as a diagnostic criterion. Molecular biology methods as a proxy for PCVD diagnoses have been extensively used in the last decade, although these techniques should be mainly considered as monitoring tools rather than diagnostic ones. What has changed over the years is the epidemiological picture of PCV-2 through the massive use of vaccination, which allowed the decrease in infectious pressure paralleled with a decrease in overall herd immunity. Consequently, the need for establishing the diagnosis of PCVD has increased lately, especially in cases with a PCV-2-SD-like condition despite vaccination. Therefore, the objective of the present review is to update the current knowledge on diagnostic criteria for PCVDs and to contextualize the interest of using molecular biology methods in the overall picture of these diseases within variable epidemiological scenarios of PCV-2 infection.

Non-antibiotic Approaches for Disease Prevention and Control in Nursery Pigs: A Scoping Review

Swine producers are encouraged to practice antibiotic stewardship by reducing their use of antibiotics belonging to classes of medical importance to humans. We conducted a scoping review of non-antibiotic approaches in the form of products or management practices that might prevent or control disease and thus reduce the need for antibiotics in nursery pigs. Our objectives were to systematically describe the research on this broad topic for the North American context, identify specific topics that could feasibly support systematic reviews, and identify knowledge gaps. A search of multiple databases identified 11,316 articles and proceedings for relevance screening. From these, 441 eligible clinical trials and observational studies were charted. The majority were clinical trials (94%). Study results from EU countries were mostly communicated through journal articles, whereas study results from the USA were mostly communicated through conference proceedings. Interventions and health outcomes were diverse. The two most frequent intervention categories were feed additives and piglet vaccines. The three most frequent outcomes reported were diarrhea, mortality, and indices of vaccine immunity. There were 13 specific topics comprising various feed additives and vaccines that might feasibly support systematic reviews. There were relatively few studies in which interventions were compared with antibiotic comparison groups and relatively few studies evaluating management practices.

Influence of the Fermented Feed and Vaccination and Their Interaction on Parameters of Large White/Norwegian Landrace Piglets

The aim of this study was to evaluate the influence of fermented with a newly isolated lactic acid bacteria (LAB) strains combination (Lactobacillus plantarum LUHS122, Lactobacillus casei LUHS210, Lactobacillus farraginis LUHS206, Pediococcus acidilactici LUHS29, Lactobacillus plantarum LUHS135 and Lactobacillus uvarum LUHS245) feed on non-vaccinated (NV) and vaccinated with Circovac porcine circovirus type 2 vaccine (QI09AA07, CEVA-PHYLAXIA Co. Ltd. Szállás u. 5. 1107 Budapest, Hungary) piglets' blood parameters, gut microbial composition, growth performance and ammonia emission. The 36-day experiment was conducted using 25-day-old Large White/Norwegian Landrace (LW/NL) piglets, which were randomly divided into four groups with 100 piglets each: S_nonV-non-vaccinated piglets fed with control group compound feed; S_V-vaccinated piglets fed with control group compound feed; RF_nonV-non-vaccinated piglets fed with fermented compound feed; RF_V-vaccinated piglets fed with fermented compound feed. Samples from 10 animals per group were collected at the beginning and end of the experiment. Metagenomic analysis showed that fermentation had a positive impact on the Lactobacillus prevalence during the post-weaning period of pigs, and vaccination had no negative impact on microbial communities. Although a higher amount of Lactobacillus was detected in vaccinated, compared with non-vaccinated groups. At the end of experiment, there was a significantly higher LAB count in the faeces of both vaccinated compared to non-vaccinated groups (26.6% for S_V and 17.2% for RF_V), with the highest LAB count in the S_V group. At the end of experiment, the S_V faeces also had the highest total bacteria count (TBC). The RF_V group had a 13.2% increase in total enterobacteria count (TEC) at the end of experiment, and the S_V group showed a 31.2% higher yeast/mould (Y/M) count. There were no significant differences in the average daily gain (ADG) among the groups; however, there were significant differences in the feed conversion ratios (FCR) between several groups: S_V vs. S_nonV (11.5% lower in the S_V group), RF_V vs. RF_nonV (10.2% lower in the RFnonV group) and S_V vs. RF_V (21.6% lower in the S_V group). Furthermore, there was a significant, very strong positive correlation between FCR and TEC in piglets' faeces (R = 0.919, p = 0.041). The lowest ammonia emission was in RF_V group section (58.2, 23.8, and 47.33% lower compared with the S_nonV, S_V and RF_nonV groups, respectively). Notably, there was lower ammonia emission in vaccinated groups (45.2% lower in S_V vs. S_nonV and 47.33% lower in RF_V vs. RF_nonV). There was also a significant, very strong positive correlation between ammonia emission and Y/M count in piglets' faeces at the end of the experiment (R = 0.974; p = 0.013). Vaccination as a separate factor did not significantly influence piglets' blood parameters. Overall, by changing from an extruded soya to cheaper rapeseed meal and applying the fermentation model with the selected LAB combination, it is possible to feed piglets without any undesirable changes in health and growth performance in a more sustainable manner. However, to evaluate the influence of vaccination and its interaction with other parameters (feed, piglets' age, breed, etc.) on piglets' parameters, additional studies should be performed and methods should be standardised to ensure the results may be compared.

Porcine circoviruses: current status, knowledge gaps and challenges

Circoviruses (CV) include some of the smallest viruses known. They were named after their circularly arranged single-stranded DNA genome with a gene encoding a conserved replicase protein on the sense strand. Circoviruses are widely distributed in mammals, fish, avian species and even insects. In pigs, four different CVs have been identified and named with consecutive numbers based on the order of their discovery: Porcine circovirus 1 (PCV1), Porcine circovirus 2 (PCV2), Porcine circovirus 3 (PCV3) and most recently Porcine circovirus 4 (PCV4). PCVs are ubiquitous in global pig populations and uninfected herds are rarely found. It is generally accepted that PCV1 is non-pathogenic. In contrast, PCV2 is considered an important, economically challenging pathogen on a global scale with comprehensive vaccination schemes in place. The role of PCV3 is still controversial several years after its discovery. Propagation of PCV3 appears to be challenging and only one successful experimental infection model has been published to date. Similarly to PCV2, PCV3 is widespread and found in many pigs regardless of their health history, including high health herds. PCV4 has only recently been discovered and further information on this virus is required to understand its potential impact. This review summarizes current knowledge on CVs in pigs and aims to contrast and compare known facts on PCVs.

Scoping Reviews, Systematic Reviews, and Meta-Analysis: Applications in Veterinary Medicine

Evidence-based decision making is a hallmark of effective veterinary clinical practice. Scoping reviews, systematic reviews, and meta-analyses all are methods intended to provide transparent and replicable ways of summarizing a body of research to address an important clinical or public health issue. As these methods increasingly are being used by researchers and read by practitioners, it is important to understand the distinction between these techniques and to understand what research questions they can, and cannot, address. This review provides an overview of scoping reviews, systematic reviews, and meta-analysis, including a discussion of the method and uses. A sample dataset and coding to conduct a simple meta-analysis in the statistical program R also are provided. Scoping reviews are a descriptive approach, designed to chart the literature around a particular topic. The approach involves an extensive literature search, following by a structured mapping, or charting, of the literature. The results of scoping reviews can help to inform future research by identifying gaps in the existing literature and also can be used to identify areas where there may be a sufficient depth of literature to warrant a systematic review. Systematic reviews are intended to address a specific question by identifying and summarizing all of the available research that has addressed the review question. Questions types that can be addressed by a systematic review include prevalence/incidence questions, and questions related to etiology, intervention efficacy, and diagnostic test accuracy. The systematic review process follows structured steps with multiple reviewers working in parallel to reduce the potential for bias. An extensive literature search is undertaken and, for each relevant study identified by the search, a formal extraction of data, including the effect size, and assessment of the risk of bias is performed. The results from multiple studies can be combined using meta-analysis. Meta-analysis provides a summary effect size, and allows heterogeneity of effect among studies to be quantified and explored. These evidence synthesis approaches can provide scientific input to evidence-based clinical decision-making for veterinarians and regulatory bodies, and also can be useful for identifying gaps in the literature to enhance the efficiency of future research in a topic area.

Real-Time PCR Detection Patterns of Porcine Circovirus Type 2 (PCV2) in Polish Farms with Different Statuses of Vaccination against PCV2

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.

Development and validation of a real-time PCR for the detection and quantification of porcine circovirus type 2

Porcine circovirus type 2 (PCV2) is a spherical and non-enveloped virus belonging to the genus Circovirus of the Circoviridae family with a single stranded circular DNA genome. This virus, already detected worldwide, has been associated to several diseases and was implicated as the etiological agent of a disease named postweaning multisystemic wasting syndrome. Several methods have been described for the detection of PCV2, being real-time PCR the most simple and reliable. As far as we know, all the real-time PCR systems described until now are based on ORF2 gene, that exhibit the highest variability. This paper reports the development and validation of a real-time PCR targeted to ORF1 and based on a TaqMan probe for the detection of porcine circovirus type 2 DNA in swine samples. Due to the lack of PCV1 samples, the ability of the test to discriminate between PCV1 and PCV2 positive samples was evaluated in silico. Estimations of 100% specificity and 100% sensitivity were obtained based on the qPCR results with panel of 81 swine samples (known PCV2-positive (n = 50); known PCV2-negative (n = 17); samples positive to other common swine viral pathogens (n = 13) and one sample from a BFDV-positive parrot (n = 1)). Intra- and inter-assay coefficients of variation obtained with three positive samples of different viral charges in five replicates or in five independent assays were below the acceptance threshold. The limit of detection determined with a recombinant plasmid containing the amplicon, led to conclude that this assay can detect at least three plasmid copies.

Porcine Circovirus Type 2 (PCV2) Vaccines in the Context of Current Molecular Epidemiology

Porcine circovirus type 2 (PCV2) is an economically important swine pathogen and, although small, it has the highest evolution rate among DNA viruses. Since the discovery of PCV2 in the late 1990s, this minimalistic virus with a 1.7 kb single-stranded DNA genome and two indispensable genes has become one of the most important porcine pathogens, and presently is subjected to the highest volume of prophylactic intervention in the form of vaccines in global swine production. PCV2 can currently be divided into five different genotypes, PCV2a through PCV2e. It is well documented that PCV2 continues to evolve, which is reflected by changes in the prevalence of genotypes. During 2006, commercial vaccines for PCV2 were introduced on a large scale in a pig population mainly infected with PCV2b. Since 2012, the PCV2d genotype has essentially replaced the previously predominant PCV2b genotype in North America and similar trends are also documented in other geographic regions such as China and South Korea. This is the second major PCV2 genotype shift since the discovery of the virus. The potential increase in virulence of the emergent PCV2 genotype and the efficacy of the current vaccines derived from PCV2a genotype against the PCV2d genotype viruses has received considerable attention. This review attempts to synthesize the understanding of PCV2 biology, experimental studies on the antigenic variability, and molecular epidemiological analysis of the evolution of PCV2 genotypes.

Serum acute phase response induced by different vaccination protocols against circovirus type 2 and Mycoplasma hyopneumoniae in piglets

The purpose of this study was to compare the acute phase reaction (APR) induced by different vaccination protocols used against Porcine Circovirus (PCV) type-2 and Mycoplasma hyopneumoniae (M.hyo), studying two acute phase proteins (APPs) and changes in rectal temperature (RT). In addition, the possible influence of the time of vaccination and breed were analysed. In the first experiment, 40 commercial crossbred piglets were vaccinated, on the day of weaning, with FLEXcombo® (group A, n=20) or Porcilis PCV® and Stellamune® One (group B, n=20). The second experiment was performed on two farms, on which 40 commercial crossbred piglets or 40 Iberian piglets were vaccinated, 7days post-weaning. On each farm one group (A, n=20) was vaccinated with FLEXcombo® and another group (B, n=20) with Porcilis® PCV-M.hyo. Blood samples were taken before, 24h and 48h after vaccination, and RT were recorded before and 8h after vaccination. Significantly higher increases in group B in RT (P<0.01) and APPs concentrations (P<0.01) were recorded at several sampling times after vaccination compared with group A. The vaccines that produced greater increases in RT also produced higher APPs increases but no influence of the day of vaccination or of the breed were found. Therefore, serum APPs concentrations differed according to the vaccine used, which may be useful, along with RT, for choosing the vaccine or protocol that produces APR of lower magnitude.