Development of a SYBR green I-based duplex real-time PCR assay for detection of pseudorabies virus and porcine circovirus 3

Advances in molecular epidemiology and detection methods of pseudorabies virus

Pseudorabies (PR), a highly contagious disease caused by the pseudorabies virus (PRV), represents a significant threat to the global swine industry. Despite the success of developed countries in controlling the PRV epidemic through swine pseudorabies eradication programs, wild boars, as a potential source of infection, still require sustained attention and effective control measures. Concurrently, there has been considerable global attention directed towards cases of PRV infection in humans. In consideration of the aforementioned factors, this paper presents a comprehensive review of recent developments in the PRV genome, epidemiology, vaccine research, and molecular detection methods. The epidemiology section presents an analysis of the transmission routes, susceptible animal groups, and geographic distribution of PRV, as well as an examination of the trend of the epidemic in recent years. In the field of vaccine research, the current development of genetically engineered vaccines is emphasized, and the immunogenicity and safety of vaccines are discussed. Moreover, the molecular detection techniques utilized to identify PRV, including immunological methods, nucleic acid detection methods, biosensors, and so forth, are presented in a systematic manner. Finally, this paper presents a comprehensive discussion of the current status of PRV-related research and offers insights into future directions, with the aim of providing a foundation for the scientific prevention and control of PRV.

A SYBR green I-based multiplex real-time PCR for simultaneous detection of pseudorabies virus, porcine circovirus 3 and porcine parvovirus

BACKGROUND

Pseudorabies virus (PRV), porcine parvovirus (PPV) and porcine circovirus 3 (PCV3) are common in swine farms in China. Single infection or co-infection with PRV, PPV and/or PCV3 was difficult to distinguish between their clinical symptoms and pathological changes. Therefore, a quick and accurate detection method is needed for epidemiological surveillance, disease management, import and export control.

METHODS

In the present study, we established a multiplex real-time PCR assay based on SYBR Green I for the simultaneous detection of PRV, PPV and PCV3 genomes.

RESULTS

PRV, PPV and PCV3 were distinguished in the same sample by their different melting temperatures (Tm), with melting peaks at 90 °C for PRV, 84 °C for PPV and 80 °C for PCV3, respectively, and other non-targeted swine pathogens did not exhibit specific melting peaks. The assay showed a high degree of linearity (R2≧0.995), and the detection limits were 4.76 copies/μL for PRV, 3.67 copies/μL for PPV, 3.07 copies/μL for PCV3 and 1.87 × 102 copies/μL for the three mixed plasmids, respectively. In this research, 81 clinical samples from pig farms in nine different regions of Guangdong Province were used to evaluate this new method. The detection rate of the multiplex real-time PCR assay was higher than that of the conventional PCR assay.

CONCLUSIONS

This multiplex real-time PCR assay could be used as a diagnostic tool that is rapid, sensitive and reliable for the detection of co-infection of PRV, PPV and PCV3 as well as for molecular epidemiological surveillance.

A pseudorabies outbreak in hunting dogs in Campania region (Italy): a case presentation and epidemiological survey

BACKGROUND

Pseudorabies is an infection of domestic and wild pigs that has occasionally been reported in dogs with fatal encephalitis. Hunting dogs are predisposed to pseudorabies exposure due to incorrect practices (administration of raw infected meat) or close contact with infected wild boars. This study described an outbreak of pseudorabies in two hunting dogs in the Campania region, southern Italy.

CASE PRESENTATION

Two hunting dogs were hospitalized after a hunting trip, with fever, itching, and self-inflicted lesions. Laboratory tests showed mild anemia and marked leukocytosis. Despite conservative therapy, both animals died 48 h after the presentation of symptoms. One of the carcasses was sent to the Department of Veterinary Medicine and Animal Production in Naples to confirm the suspicion of pseudorabies. DNA was extracted from different matrices and used as a template for real-time PCR to detect PRV. Several samples (brain, cerebellum, brainstem, lung, and liver) tested positive. Subsequent sequence analyses of glycoprotein E from DNA extracted from the brain stem revealed a sequence similarity to those described in previous cases of pseudorabies in dogs in Italy, France and Belgium. One month after the outbreak, blood samples were collected from 42 dogs belonging to the same hunting team and from 245 dogs (cohort population) living in the Campania region. All samples were tested with two commercial ELISAs to detect seroconversion against glycoproteins B and E. A seroprevalence of 19% was observed in the hunting team affected by the outbreak, while only 0.8% was observed in the regional dog population.

CONCLUSIONS

The data reported in this study demonstrate potential exposure to PRV by dead-end hosts, particularly hunting dogs. The sequencing results indicated the homogeneity of PRV strains circulating in the different Italian regions.

Detection of selected pathogens in reproductive tissues of wild boars in the Campania region, southern Italy

Monitoring disease among wildlife is critical to preserving health in both domestic animals and wildlife, and it becomes much more critical when the diseases cause significant economic damage to the livestock industry or threaten public health. Given the continuous increase in populations and its role as a reservoir for several infections, wild boar (Sus scrofa) requires special attention regarding disease surveillance and monitoring. In this study, we investigated the molecular prevalence of selected pathogens in the wild boar population of Campania, southern Italy. The prevalence of pathogens causing reproductive problems in pigs (Sus domesticus), including porcine parvovirus (PPV), porcine circovirus types 2 and 3 (PCV-2 and PCV-3), pseudorabies virus (PRV), Coxiella burnetii, and Brucella suis, was evaluated by testing the reproductive organs collected from 63 wild boars with polymerase chain reaction. The most common pathogens were PPV (44.4%) and two porcine circoviruses (14.3%). PRV and C. burnetii, on the other hand, showed a significantly lower prevalence (1.6%). No reproductive organs tested were positive for B. suis. Risk factor analysis revealed a correlation between age and PCV-2 positivity, with animals less than 12 months old having significantly higher prevalence rates.Our findings suggest that wild boars hunted in the Campania region harbour several infections potentially transmissible to other mammals' reproductive tracts. Furthermore, our results emphasized the importance of strict adherence to biosecurity protocols on domestic swine farms, especially on free-range farms, to avoid interactions between domestic and wild animals.

First molecular detection and genetic characterization of porcine circovirus 4 in the Gansu Province of China

Since its initial discovery in the Hunan province of China, genomic DNA of porcine circovirus 4 (PCV4) has been detected in pigs across multiple provinces in China, as well as in South Korea. However, the prevalence of porcine circovirus type 4 in Gansu Province, China, remains unknown. To address this gap, we undertook an extensive study where we gathered 121 clinical samples displaying diverse clinical manifestations from pig farms in Gansu Province between 2022 and 2023. Employing a real-time fluorescence quantification method, we identified the presence of PCV4 genome. Out of the 121 clinical samples analyzed, 13 samples tested positive for PCV4, resulting in a positive rate of 10.74% (13/121). This finding confirms the presence of PCV4 in pig farms within Gansu Province, China. Furthermore, we successfully sequenced and analyzed the complete genomes of two distinct PCV4 strains, comparing them with 60 reference sequences archived in the GenBank database. The results revealed a high nucleotide homology (98.2-98.8%) between the strains obtained in this study and the PCV4 reference strains, indicating a relatively low evolutionary rate of the PCV4 genome. Phylogenetic analysis revealed that two strains in this study belong to PCV4a and PCV4c. As far as we know, this study marks the inaugural report on the molecular identification and genomic attributes of PCV4 in Gansu Province, China, offering valuable insights for devising preventive and control strategies against this emerging virus.

Fast and sensitive differential diagnosis of pseudorabies virus-infected versus pseudorabies virus-vaccinated swine using CRISPR-Cas12a

IMPORTANCE

Pseudorabies virus (PRV) causes high mortality and miscarriage rates in the infected swine, and the eradication policy coupled with large-scale vaccination of live attenuated vaccines has been adopted globally against PRV. Differential diagnosis of the vaccinated and infected swine is highly demanded. Our multienzyme isothermal rapid amplification (MIRA)-Cas12a detection method described in this study can diagnose PRV with a superior sensitivity comparable to the quantitative PCR (qPCR) and a competitive detection speed (only half the time as qPCR needs). The portable feature and the simple procedure of MIRA-Cas12a make it easier to deploy for clinical diagnosis, even in resource-limited settings. The MIRA-Cas12a method would provide immediate and accurate diagnostic information for policymakers to respond promptly.

The Significance and Importance of dPCR, qPCR, and SYBR Green PCR Kit in the Detection of Numerous Diseases

Digital PCR (dPCR) is the latest technique that has become commercially accessible for various types of research. This method uses Taq polymerase in a standard polymerase chain reaction (PCR) to amplify a target DNA fragment from a complex sample, like quantitative PCR (qPCR) and droplet digital PCR (dd- PCR). ddPCR may facilitate microRNA (miRNA) measurement, particularly in liquid biopsy, because it has been proven to be more effective and sensitive, and in this method, ddPCR can provide an unprecedented chance for deoxyribonucleic acid (DNA) methylation research because of its capability to increase sensitivity and precision over conventional PCR-based methods. qPCR has also been found to be a valuable standard technique to measure both copy DNA (cDNA) and genomic DNA (gDNA) levels, although the finding data can be significantly variable and non-reproducible without relevant validation and verification of both primers and samples. The SYBR green quantitative real-time PCR (qPCR) method has been reported as an appropriate technique for quantitative detection and species discrimination, and has been applied profitably in different experiments to determine, quantify, and discriminate species. Although both TaqMan qRT-PCR and SYBR green qRT-PCR are sensitive and rapid, the SYBR green qRT-PCR assay is easy and the TaqMan qRT-PCR assay is specific but expensive due to the probe required. This review aimed to introduce dPCR, qPCR, SYBR green PCR kit, and digital PCR, compare them, and also introduce their advantages in the detection of different diseases.

Pathogenicity and immune modulation of porcine circovirus 3

Porcine circoviruses (PCVs) are members of the genus Circovirus of the family Circoviridae, and four species of PCVs have been discovered and named PCV1-PCV4, respectively. With the first report of PCV3 in America in 2016, the pathogenic variant was found to be associated with various clinical features, called porcine circovirus associated disease (PCVAD), including multisystemic inflammation, porcine dermatitis and nephropathy syndrome (PDNS), reproductive disorders, respiratory or digestive disorders. Increasing experimental data have shown that PCV3 is widespread around the world, but the failure of virus isolation and propagation has put obstacles in the way of PCV3 research. Moreover, a large number of reports demonstrate that PCV3 usually co-infects with other pathogens in pigs. Thus, whether PCV3 alone causes clinical manifestations needs to be fully discussed. In addition, the host cell immune response was activated during PCV3 infection, and PCV3-encoded proteins may regulate immune responses to facilitate its replication. An in-depth understanding of PCV3 pathogenesis and immune regulation strategies is critical for PCVAD prevention. In this review, the advances in pathogenicity and innate immune modulation of PCV3 were summarized, which could deepen the understanding of this virus and PCV3-related diseases.

Characterization of a gE/gI/TK gene-deleted pseudorabies virus variant expressing the Cap protein of porcine circovirus type 2d

Porcine circovirus type 2 (PCV2) plays a key role in the etiology of PCV2-associated disease (PCVAD), and its predominant strain is PCV2d which is not completely controlled by most commercially available vaccines against PCV2a strains. Pseudorabies (PR) caused by pseudorabies virus (PRV) variants re-emerged in Bartha-K61 vaccine-immunized swine herds in late 2011, which brought considerable losses to the global pig husbandry. Therefore, it is significantly important to develop a safe and effective vaccine against both PCV2d and PRV infection. In the present study, the PCV2d ORF2 gene was amplified by PCR, and cloned into the BamHI site of PRV transfer plasmid pG vector to obtain the recombinant transfer plasmid pG-PCV2dCap-EGFP. Subsequently, it was transfected into ST cells infected with the three gene deleted PRV variant strain NY-gE-/gI-/TK- to generate a recombinant virus rPRV NY-gE-/gI-/TK-/PCV2dCap+/EGFP+, and then the EGFP gene was knocked out to harvest the rPRV NY-gE-/gI-/TK-/PCV2dCap+ using gene-editing technology termed CRISPR/Cas9 system. The recombinant virus rPRV NY-gE-/gI-/TK-/PCV2dCap+ had similar genetic stability and proliferation characteristics to the parental PRV as indicated by PCR and one-step growth curve test, and the expression of Cap was validated by Western blot. In animal experiment, higher PCV2-specific ELISA antibodies and detectable PCV2-specific neutralizing antibodies could be elicited in mice immunized with rPRV NY-gE-/gI-/TK-/PCV2dCap+ compared to commercial PCV2 inactivated vaccine. Moreover, the recombinant virus rPRV NY-gE-/gI-/TK-/PCV2dCap+ significantly reduced the viral loads in the hearts, livers, spleens, lungs, and kidneys in mice following a virulent PCV2d challenge. Mice immunized with rPRV NY-gE-/gI-/TK-/PCV2dCap+ developed comparable PRV-specific humoral immune responses and provided complete protection against a lethal PRV challenge. Together, the rPRV NY-gE-/gI-/TK-/PCV2dCap+ recombinant strain has strong immunogenicity.

First molecular detection and genetic analysis of porcine circovirus 4 in the Southwest of China during 2021–2022

Porcine circovirus 4 (PCV4) was identified in 2019 as a novel circovirus species and then proved to be pathogenic to piglets. However, there is a lack of its prevalence in the Southwest of China. To investigate whether PCV4 DNA existed in the Southwest of China, 374 samples were collected from diseased pigs during 2021–2022 and detected by a real-time PCR assay. The results showed that the positive rate of PCV4 was 1.34% (5/374) at sample level, and PCV4 was detected in two of 12 cities, demonstrating that PCV4 could be detected in pig farms in the Southwest of China, but its prevalence was low. Furthermore, one PCV4 strain (SC-GA2022ABTC) was sequenced in this study and shared a high identity (98.1–99.7%) with reference strains at the genome level. Combining genetic evolution analysis with amino acid sequence analysis, three genotypes PCV4a, PCV4b, and PCV4c were temporarily identified, and the SC-GA2022ABTC strain belonged to PCV4c with a specific amino acid pattern (239V for Rep protein, 27N, 28R, and 212M for Cap protein). Phylogenetic tree and amino acid alignment showed that PCV4 had an ancient ancestor with mink circovirus. In conclusion, the present study was the first to report the discovery and the evolutionary analysis of the PCV4 genome in pig herds of the Southwest of China and provide insight into the molecular epidemiology of PCV4.

Pseudorabies Virus: From Pathogenesis to Prevention Strategies

Pseudorabies (PR), also called Aujeszky’s disease (AD), is a highly infectious viral disease which is caused by pseudorabies virus (PRV). It has been nearly 200 years since the first PR case occurred. Currently, the virus can infect human beings and various mammals, including pigs, sheep, dogs, rabbits, rodents, cattle and cats, and among them, pigs are the only natural host of PRV infection. PRV is characterized by reproductive failure in pregnant sows, nervous disorders in newborn piglets, and respiratory distress in growing pigs, resulting in serious economic losses to the pig industry worldwide. Due to the extensive application of the attenuated vaccine containing the Bartha-K61 strain, PR was well controlled. With the variation of PRV strain, PR re-emerged and rapidly spread in some countries, especially China. Although researchers have been committed to the design of diagnostic methods and the development of vaccines in recent years, PR is still an important infectious disease and is widely prevalent in the global pig industry. In this review, we introduce the structural composition and life cycle of PRV virions and then discuss the latest findings on PRV pathogenesis, following the molecular characteristic of PRV and the summary of existing diagnosis methods. Subsequently, we also focus on the latest clinical progress in the prevention and control of PRV infection via the development of vaccines, traditional herbal medicines and novel small RNAs. Lastly, we provide an outlook on PRV eradication.

The Probiotic Attributes and Anti-pseudorabies Virus Evaluation of Lactobacillus Isolates

The emergence of pseudorabies virus (PRV) variants brings serious harm to the swine industry, and its effective treatments are limited at present. As one of the probiotics, the Lactobacillus species have beneficial characteristics of regulating the balance of intestinal flora, inhibiting the growth of pathogenic bacteria and viruses' proliferation, and improving self-immunity. In this study, Lactobacillus plantarum HN-11 and Lactobacillus casei HN-12 were selected and identified through morphology observation, Gram stain microscopy, 16S rRNA sequencing analysis, and specific amplification of the recA gene and pheS gene. All tested isolates exhibited rapid adaptation to the different conditions, excellent acid, and bile tolerance, and sensitivity to Salmonella, Staphylococcus aureus, and Escherichia coli. The antibiotic susceptibility assay displayed the isolates sensitive to most antibiotics and resistant to Lincomycin and Norfloxacin. Moreover, the supernatants of HN-11 and HN-12 inhibited PRV proliferation in ST cells. The results of animal experiments showed that supplementing the challenged mice with the supernatants of Lactobacillus isolates in advance delayed the course of the disease. PRV was detected in the heart, liver, spleen, lung, kidney, and brain tissues of dead mice in the test groups, and its copies in the lungs were significantly decreased compared with the control mice (P < 0.05). These findings proved the advantages of L. plantarum and L. casei as potential probiotic cultures, which could provide a basis for its application in microecological preparations and functional formulations.

Isolation and Phylogenetic Analysis of Reemerging Pseudorabies Virus Within Pig Populations in Central China During 2012 to 2019

To understand the biological characteristics of the reemerging pseudorabies virus (PRV) strains, a total of 392 tissue samples were collected from diseased pigs during reemerging PR outbreaks between 2012 and 2019 on farms in central China where swine had been immunized with Bartha-K61 and 51 (13. 01%) were positive for the gE gene by PCR. Sixteen PRV strains were isolated and caused clinical symptoms and death in mice. Subsequently, gE, gC, gB, and gD complete genes were amplified from the 16 PRV isolates and sequenced. Phylogenetic analysis based on these four gene sequences shows that the 16 PRV isolates were more closely related to the Chinese PRV variants (after 2012) but genetically differed from early Chinese PRV isolates (before 2012). Sequence analysis reveals that PRV isolates exhibited amino acid insertions, substitutions, or deletions compared with early Chinese PRV isolates and European–American PRV strains. In addition, this is the first report that eight isolates (8/16) in this study harbor a unique amino acid substitution at position 280 (F to L) of the gC protein, and six isolates have an amino acid substitution at position 338 (A to V) of the gD protein compared with the Chinese PRV variants. The emulsion containing inactivated PRV NY isolate could provide complete protection against the NY isolate. This study might enrich our understanding of the evolution of reemerging PRV strains as well as pave the way for finding a model virus to develop a novel vaccine based on reemerging PRV strains.

Recent Progress on Epidemiology and Pathobiology of Porcine Circovirus 3

The recently discovered porcine circovirus 3 (PCV3) belongs to the Circovirus genus of the Circoviridae family together with the other three PCVs, PCV1, PCV2, and PCV4. As reported, PCV3 can infect pig, wild boar, and several other intermediate hosts, resulting in single or multiple infections in the affected animal. The PCV3 infection can lead to respiratory diseases, digestive disorders, reproductive disorders, multisystemic inflammation, and immune responses. Up to now, PCV3 infection, as well as the disease caused by PCV3, has been reported in many swine farms worldwide with high positive rates, which indicates that the virus may be another important pathogen in the swine industry. Therefore, we reviewed the current progress on epidemiology and pathobiology of PCV3, which may provide the latest knowledge of the virus and PCV3-related diseases.

Electrochemical investigations for COVID-19 detection-A comparison with other viral detection methods

Virus-induced infection such as SARS-CoV-2 is a serious threat to human health and the economic setback of the world. Continued advances in the development of technologies are required before the viruses undergo mutation. The low concentration of viruses in environmental samples makes the detection extremely challenging; simple, accurate and rapid detection methods are in urgent need. Of all the analytical techniques, electrochemical methods have the established capabilities to address the issues. Particularly, the integration of nanotechnology would allow miniature devices to be made available at the point-of-care. This review outlines the capabilities of electrochemical methods in conjunction with nanotechnology for the detection of SARS-CoV-2. Future directions and challenges of the electrochemical biosensors for pathogen detection are covered including wearable and conformal biosensors, detection of plant pathogens, multiplexed detection, and reusable biosensors for on-site monitoring, thereby providing low-cost and disposable biosensors.

Prevalence and genetic analysis of porcine circovirus type 2 (PCV2) and type 3 (PCV3) between 2018 and 2020 in central China

Porcine circovirus type 2 (PCV2) is the causative agent of porcine circovirus-associated diseases (PCVAD), causing substantial economic losses to the swine industry worldwide. PCV3, as a recently discovered virus, is associated with porcine dermatitis, nephropathy syndrome, reproductive failure, congenital tremors, and other clinical symptoms. To further investigate the epidemic profile and genetic diversity of the two viruses, a total of 198 samples from swine at various growth stages suspected for PCVAD on 55 different pig farms between 2018 and 2020 were analyzed for presence of PCV2 and PCV3 by using a multiplex real-time PCR assay. Among the 198 samples, 113 (57.07%) and 72 (36.36%) were positive for PCV2 and PCV3 respectively, and 39 (19.7%) were positive for PCV2 and PCV3 co-infection. Subsequently, whole genome sequences of 34 PCV2 and 19 PCV3 strains were obtained from 30 and 19 clinical samples, respectively. Of these, 8 PCV2 strains belonged to PCV2a, 10 belonged to PCV2b and 16 belonged to PCV2d, indicating PCV2d was the predominant PCV2 genotype circulating in central China. Furthermore, co-infection of different PCV2 genotype strains was identified in three samples (JZ-4, KF-2 and JY-1), and a cross-recombination was found in the ORF2 region of the sequenced 13 PCV2d strains whose putative parental strains were LN6/1999 (MF278777) and MEX/41238/2014 (KT795287) strains. The phylogenetic analysis of PCV3 showed high nucleotide identity (>98%) among sequences obtained in this study and reference sequences. These data will aid our understanding of the molecular epidemiology and evolution of PCV2 and PCV3.

Comparative immunopathogenesis and biology of recently discovered porcine circoviruses

Porcine circoviruses are important pathogens of production swine. Porcine circovirus type 1 (PCV1) is non-pathogenic, and discovered as a contaminant of a porcine kidney cell line, PK-15. The discovery of pathogenic variant, PCV2, occurred in the late 90s in association with post-weaning multi-systemic wasting disease syndrome (PMWS), which is characterized by wasting, respiratory signs and lymphadenopathy in weanling pigs. A new PCV type, designated as PCV3, was discovered in 2016, in pigs manifesting porcine dermatitis and nephropathy syndrome (PDNS), respiratory distress and reproductive failure. Pathological manifestations of PCV3 Infections include systemic inflammation, vasculitis and myocarditis. A fourth PCV type, PCV4, was identified in 2020 in pigs with PDNS, respiratory and enteric signs. All the pathogenic PCV types are detected in both healthy and morbid pigs. They cause chronic, systemic infections with various clinical manifestations. Dysregulation of the immune system homeostasis is a pivotal trigger for pathogenesis in porcine circoviral infections. While the study of PCV3 immunobiology is still in its infancy lessons learned from PCV2 and other circular replication-associated protein (Rep)-encoding single stranded (ss) (CRESS) DNA viruses can inform the field of exploration for PCV3. Viral interactions with the innate immune system, interference with dendritic cell function coupled with the direct loss of lymphocytes compromises both innate and adaptive immunity in PCV2 infections. Dysregulated immune responses leading to the establishment of a pro-inflammatory state, immune complex associated hypersensitivity, and the necrosis of lymphocytes and immune cells are key features of PCV3 immunopathogenesis. A critical overview of the comparative immunopathology of PCV2 and PCV3/4, and directions for future research in the field are presented in this review.

A novel paper biosensor based on Fe3O4@SiO2-NH2and MWCNTs for rapid detection of pseudorabies virus

In this study, a novel paper biosensor based on Fe₃O₄@SiO₂-NH₂magnetic polymer microspheres and multi walled carbon nanotubes (MWCNTs) for rapid detection of pseudorabies virus (PRV) was first developed. Fe₃O₄@SiO₂-NH₂were functionalized with PRV antibody and doped in cellulose nitrate paper to fabricate the magnetic paper biosensor with good magnetic response and biocompatibility. Using MWCNTs to build conductive network of sensors, PRV antigen binds specifically to the immunomagnetic microspheres on the sensor, and the resulting immune complex changes the magnetic domain structure of the sensor and the structural gap of MWCNTs, causing the magnetic property and impedance change. TEM and EDS characterization proved that the biosensor was successfully doped with Fe₃O₄@SiO₂-NH₂and effectively recognized PRV. Under optimized conditions, the impedance variation was found to be linearly related to the logarithm value of PRV concentrations in the range of 10-1 mg ml^-1, with the detection limit of 10 ng ml^-1. This paper biosensor demonstrated advantages of portability, high sensitivity and specificity, providing a valuable method for early control of PRV.

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.

Pseudorabies (Aujeszky's disease) virus DNA detection in swine nasal swab and oral fluid specimens using a gB-based real-time quantitative PCR

In this study, the detection of PRV DNA in nasal swab (n = 440) and oral fluid (n = 1,545) samples collected over time from experimentally PRV vaccinated and/or PRV inoculated pigs (n = 40) was comparatively evaluated by real-time PCR. Serum samples (n = 440) were tested by PRV gB/gE blocking ELISAs (Pseudorabies Virus gB Antibody Test Kit and Pseudorabies Virus gpI Antibody Test Kit, IDEXX Laboratories, Inc., Westbrook, ME) to monitor PRV status over time. Following exposure to a gE-deleted modified live vaccine (Ingelvac® Aujeszky MLV, Boehringer Ingelheim, Ridgefield, CT) and/or a wild-type virus (3 CR Ossabaw), PRV gB DNA was detected in oral fluid specimens in a pattern similar to that of nasal swabs. For quantitative analyses, PRV PCR quantification cycle (Cq) results were re-expressed as "efficiency standardized Cqs (ECqs)" as a function of PCR efficiency using plate-specific positive amplification controls. ROC analyses of the PRV gB PCR ECqs results showed a similar performance of the PRV gB PCR for nasal swab and oral fluid specimens (area under the ROC curve = 85 % vs 83 %) and, based on an ECq cutoff of 0.01 a diagnostic specificity of 100 % and diagnostic sensitivities for oral fluid and nasal swab specimens of 53 % (95 % CI: 43 %, 62 %) and 70 % (95 % CI: 55 %, 83 %), respectively. Thus, the results described herein demonstrated the detection of PRV gB DNA in swine oral fluid and supported the use of this specimen in PRV diagnosis and surveillance.