One world--one health: the threat of emerging swine diseases. An Asian perspective

Phylogenetic analyses and antigenic characterization of foot-and-mouth disease virus PanAsia lineage circulating in China between 1999 and 2023

Foot-and-mouth disease (FMD) is one of the most important transboundary animal diseases caused by foot-and-mouth disease virus (FMDV), leading to significant economic losses worldwide. The first report of PanAsia lineage of FMDV in China was in 1999. Since 2011, 18 outbreaks attributed to PanAsia lineage viruses have been reported across 7 provinces or municipality in China. Phylogenetic analysis indicated that these PanAsia strains were clustered into three distinct clades (clade 1, clade 2, and clade 3), with nucleotide homology ranging from 91.4% to 100%. The outbreaks of FMD caused by clade 1 strains occurred around 1999 when this lineage was prevalent globally. Clade 2 strains dominated from 2011 to 2013, while clade 3 strains were prevalent during 2018-2019, sharing only 93% homology with clade 2 strains and 91% with clade 1 strains. Tracing analysis showed that these outbreaks represented 3 distinct introductions of PanAsia viruses into China. Virus neutralization tests (VNT) have demonstrated that current commercial vaccines are effective to protect susceptible animals against these strains (r1 > 0.3). However, the growing demand for livestock has promoted animal movement and encouraged the exchange of products, services, and materials between countries, thereby heightening the risk of exotic strain incursions. Therefore, it is imperative to reinforce border controls and limit animal movements among various Asian countries continually to reduce the risk of new transboundary diseases, such as FMD incursion. Additionally, PanAsia-2 strains need to be taken seriously to prevent its incursions, and the relevant vaccines against PanAsia-2 strains needs to be stockpiled in preparation for any possible incursion.

Genetic evolution and phylogenetic analysis of porcine epidemic diarrhea virus strains circulating in and outside China with reference to a wild type virulent genotype CHYJ130330 reported from Guangdong Province, China

During the last decade, porcine epidemic diarrhea virus has detrimental consequences on swine industry, due to severe outbreaks especially in the suckling piglets. In March 2013, an outbreak was reported on a commercial swine farm in Guangdong Province, Southern China. A wild-type PEDV strain named as CHYJ130330 was identified, complete genome was sequenced and deposited in GenBank (accession no. KJ020932). The molecular epidemiological including evolutionary characteristics and pathogenicity assessment were explored during this study with particular interest and focus to develop this candidate strain for new vaccine. The isolates from China pre- and post-2013 shared 96.5-97.2% and 97-99% nt identity respectively with wild-type CHYJ130330 strain which during experimental studies has demonstrated high virulence and 100% mortality in 104 TCID50 group piglets within 5 days. The 22 reference strains selected from other parts of the world shared 98-99% identity with our sequence except Chinese (CV777) and S. Korean (vir.DR13, SM98 and atten.DR13) strains sharing 96.8, 97.6, 96.6 and 97.1% identity respectively. The phylogenetic tree revealed most strains reported after 2013 in GII genogroup while the prototype (CV777), S.korean and earlier Chinese (JS2008, 85-7mutant, Atten.vaccine, SD-M, LZC and CH/S) were GI Group. The amino acid sequence of CHYJ130330 E and M protein is highly conserved while ORF3 and N protein having 9 and 17 amino acid substitutions respectively in comparison to CV777 strain. The comparison of full length genome and the structural proteins revealed variations signifying that PEDV variant strains are still the main source of outbreaks in spite of continuous vaccination and also explain the variable trend of large scale outbreaks during this decade as compared to sporadic tendency of disease found before 2010. It is evident from this study that Chinese strains display significant level of mixing with the strains reported from other countries. The strain CHYJ130330 was also adapted successfully to Vero cell line and has shown high virulence in piglets. The information/findings will be helpful to develop a strategy for control of PEDV and have also shown that CHYJ130330 strain has strong virulence and is a more popular clinical strain in recent years, which has the potential to be developed into PEDV vaccine.

Isolation and characterization of porcine epidemic diarrhea virus with a novel continuous mutation in the S10 domain

Porcine epidemic diarrhea virus (PEDV), which re-emerged in China in 2010, has caused severe economic losses to the global pig industry. In this study, a PEDV strain, designated PEDV WMB, was isolated from piglets with severe diarrhea on a pig farm in Henan Province of China. Whole-genome sequencing and analysis revealed that the PEDV WMB strain belongs to subtype G2c and has a unique continuous mutation in the S1⁰ antigenic epitope of the S protein. Moreover, the virus-neutralization (VN) test indicated that polyclonal antibodies against the S1⁰ protein of other G1 and G2 strains showed reduced VN reactivity to PEDV WMB. The pathogenicity of PEDV WMB was further investigated in 3 day-old piglets. PEDV infection-related clinical symptoms and morphological lesions were observed and confirmed by histopathological and immunohistochemical examination (IHC). These results illustrated that continuous mutation of the S1⁰ epitope might affect the immunogenicity or pathogenicity of PEDV, providing evidence of the need to monitor the genetic diversity of the virus and develop effective measures to prevent and control PEDV.

Based on the Results of PEDV Phylogenetic Analysis of the Most Recent Isolates in China, the Occurrence of Further Mutations in the Antigenic Site S1° and COE of the S Protein Which Is the Target Protein of the Vaccine

The continuous challenge of existing vaccine systems by porcine epidemic diarrhea virus (PEDV) variant strains in recent years, it caused significant economic losses in the global swine industry. A PEDV virulent strain CH/HLJBQL/2022 was successfully isolated in China in this study. A genome-wide based phylogenetic analysis suggests that CH/HLJBQL/2022 belongs to the GII subtype, and 96.3%–99.6% homology existed in the whole genomes of other strains. For the first time, simultaneous mutations of four amino acids were found in the highly conserved membrane (M) and nucleocapsid (N) proteins, as well as five amino acid mutations that differed from the vast majority of strains in the spike (S) protein. Mutations in the M and S proteins were found to produce coils with different angles by building 2D and 3D structural models. Epitope analysis indicated that the isolates produced specific changes and that the transmembrane function of the M protein had not been affected. In addition, typing markers exist during strain evolution, but isolates are using the fusion of specific amino acids from multiple variant strains to add additional features, as also demonstrated by protein alignments and 3D models of numerous subtype strains. These results suggest that aa mutations in the M and S proteins may have changed the structure and antigenic epitope of the isolates and PEDV is evolving again on the basis of variants that have been found to counteract the immune network of the new vaccine.

A new PEDV strain CH/HLJJS/2022 can challenge current detection methods and vaccines

BACKGROUND

Porcine epidemic diarrhea virus (PEDV) variant strains cause great economic losses to the global swine industry. However, vaccines do not provide sufficient protection against currently circulating strains due to viral mutations. This study traced the molecular characteristics of the most recent isolates in China and aimed to provide a basis for the prevention and treatment of PEDV.

METHODS

We obtained samples from a Chinese diarrheal swine farm in 2022. Reverse transcription polymerase chain reaction and immunofluorescence were used to determine the etiology, and the full-length PEDV genome was sequenced. Nucleotide similarity was calculated using MEGA to construct a phylogenetic tree and DNASTAR. Mutant amino acids were aligned using DNAMAN and modeled by SWISS-MODEL, Phyre2 and FirstGlance in JMOL for protein tertiary structure simulation. Additionally, TMHMM was used for protein function prediction.

RESULTS

A PEDV virulent strain CH/HLJJS/2022 was successfully isolated in China. A genome-wide based phylogenetic analysis suggests that it belongs to the GII subtype, and 96.1-98.9% homology existed in the whole genomes of other strains. For the first time, simultaneous mutations of four amino acids were found in the highly conserved membrane (M) and nucleocapsid (N) proteins, as well as eight amino acid mutations that differed from the vast majority of strains in the spike (S) protein. Three of the mutations alter the S-protein spatial structure. In addition, typing markers exist during strain evolution, but isolates are using the fusion of specific amino acids from multiple variant strains to add additional features, as also demonstrated by protein alignments and 3D models of numerous subtype strains.

CONCLUSION

The newly isolated prevalent strain CH/HLJJS/2022 belonged to the GII subtype, and thirteen mutations different from other strains were found, including mutations in the highly conserved m and N proteins, and in the S1° and COE neutralizing epitopes of the S protein. PEDV is breaking through original cognitions and moving on a more complex path. Surveillance for PEDV now and in the future and improvements derived from mutant strain vaccines are highly warranted.

Prevention and Control of Porcine Epidemic Diarrhea: The Development of Recombination-Resistant Live Attenuated Vaccines

Porcine epidemic diarrhea (PED), causing up to 100% mortality in neonatal pigs, is a highly contagious enteric disease caused by PED virus (PEDV). The highly virulent genogroup 2 (G2) PEDV emerged in 2010 and has caused huge economic losses to the pork industry globally. It was first reported in the US in 2013, caused country-wide outbreaks, and posed tremendous hardship for many pork producers in 2013–2014. Vaccination of pregnant sows/gilts with live attenuated vaccines (LAVs) is the most effective strategy to induce lactogenic immunity in the sows/gilts and provide a passive protection via the colostrum and milk to suckling piglets against PED. However, there are still no safe and effective vaccines available after about one decade of endeavor. One of the biggest concerns is the potential reversion to virulence of an LAV in the field. In this review, we summarize the status and the major obstacles in PEDV LAV development. We also discuss the function of the transcriptional regulatory sequences in PEDV transcription, contributing to recombination, and possible strategies to prevent the reversion of LAVs. This article provides insights into the rational design of a promising LAV without safety issues.

Potential zoonotic swine enteric viruses: The risk ignored for public health

Swine could serve as a natural reservoir for a large variety of viruses, including potential zoonotic enteric viruses. The presence of viruses with high genetic similarity between porcine and human strains may result in the emergence of zoonotic or xenozoonotic infections. Furthermore, the globalization and intensification of swine industries exacerbate the transmission and evolution of zoonotic viruses among swine herds and individuals working in swine-related occupations. To effectively prevent the public health risks posed by zoonotic swine enteric viruses, designing, and implementing a comprehensive measure for early diagnosis, prevention, and mitigation, requires interdisciplinary a collaborative ''One Health" approach from veterinarians, environmental and public health professionals, and the swine industry. In this paper, we reviewed the current knowledge of selected potential zoonotic swine enteric viruses and explored swine intensive production and its associated public health risks.

Molecular characterization of porcine epidemic diarrhoea virus (PEDV) in Poland reveals the presence of swine enteric coronavirus (SeCoV) sequence in S gene

Porcine epidemic diarrhoea (PED) is a highly contagious enteric viral disease of pigs with a high morbidity and mortality rate, which ultimately results in huge economic losses in the pig production sector. The etiological agent of this disease is the porcine epidemic diarrhoea virus (PEDV) which is an enveloped, positive single-stranded RNA virus. The aim of this study was to perform molecular characterization of PEDV to identify the strains circulating in Poland. In this study, 662 faecal samples from 2015 to 2021 were tested with reverse transcription quantitative real-time PCR (RT-qPCR) and the results showed that 3.8% of the tested samples revealed a positive result for PEDV. A phylogenetic analysis of the complete genome and complete S gene sequences showed that Polish PEDV strains belonged to the G1b (S-INDEL) subgroup and were closely related to the European PEDV strains isolated from 2014 to 2019. Furthermore, RDP4 analysis revealed that the Polish PEDV strains harboured a recombinant fragment of ~400 nt in the 5' end of S gene with PEDV and swine enteric coronavirus (SeCoV) being the major and minor parents, respectively. Antigenic analysis showed that the aa sequences of neutralizing epitopes were conserved among the Polish PEDV strains. Only one strain, #0100/5P, had a unique substitution in the COE epitope. However, Polish PEDV strains showed several substitutions, especially in the COE antigen, as compared to the classical strain CV777. To the best of our knowledge, this is the first report concerning the molecular characterization of porcine epidemic diarrhoea virus strains, as well as the first phylogenetic analysis for PEDV in Poland.

Is One Health a Viable Strategy in Animal Health Litigation: Evidence from Civil Lawsuits in China

Simple Summary

Strategic litigation launched to protect animal welfare worldwide branches out with several tactical themes: environmental protection, child abuse, veterinarian malpractice, product liability and quasi-family member. Currently, the litigation strategy themed in One Health has been observed in legal practice in Chinese mainland. Using 1520 zoonosis related civil lawsuit judgments, this study aimed to assess the effectiveness of this litigation strategy in animal health cases from Chinese mainland. It has been confirmed that using the litigation strategy themed in One Health results in more successful outcomes and larger damage awards, so there might be a practical value in using this strategy in animal welfare lawsuits.

Abstract

Several litigation strategies are used to gain support from courts in order to protect animals. While the emerging litigation strategy themed in One Health stimulates judicial protection in the animal health sector, little is known about whether and how such strategies are supported by courts. In this article, we investigate how animal welfare litigation strategies influence judge’s choices within their discretion. We argue that litigators equipped with the litigation strategy themed in One Health are placed in an advantageous position in animal health cases, but that this tendency varies markedly across zoonoses. Specifically, we suggest that litigators utilizing One Health’s litigation strategy are associated with higher probabilities to win, whereas normal litigators are not. Further, we propose that litigators equipped with the One Health litigation strategy are awarded more damages from judges. We test and find support for our predictions using a cross sectional dataset of civil lawsuit cases centering on the animal health industry in Chinese mainland. Our findings indicate that courts indeed were persuaded by the One Health litigation strategy, even when bound by the discretion rules. At the same time, we suggest that for advocates who would like to litigate for animal welfare in the animal health sector, the litigation strategy themed in One Health might have potentially positive implications.

Antiviral activity of portulaca oleracea L. extracts against porcine epidemic diarrhea virus by partial suppression on myd88/NF-κb activation in vitro

Porcine epidemic diarrhea virus (PEDV), especially variants, causes a highly contagious enteric disease which could give rise to huge economic losses in the swine industry worldwide. Portulaca oleracea L. has been reported to regulate intestine disease and involved in viral infections. However, the underlying mechanisms of Portulaca oleracea L. extracts against PEDV have not been fully elucidated. In this study, the antiviral effects and potential mechanisms of Portulaca oleracea L. extracts against PEDV were investigated in vitro. We first examined the inhibitory effects of different Portulaca oleracea L. extracts on the PEDV(JX-16 strain) in vitro and found that the water extract of Portulaca oleracea L.(PO)could significantly inhibit PEDV replication by 92.73% on VH cells and 63.07% on Vero cells. Furthermore, time-course analysis showed PO inhibited PEDV replication during the adsorption period of infectious cycle. Western blot and indirect immunofluorescence assay indicated that PO down-regulated the S protein expression in a dose-dependent manner. In addition, our results demonstrated the ability of PO to inhibit PEDV replication in VH cells by down-regulating the cytokine levels (TNF-α,IL-22 and IFN-α) and inhibiting the NF-κB signaling pathway activated by PEDV. Thus, Portulaca oleracea L extracts have potential utility in the preventive and therapeutic strategies for PEDV infection.

A serological survey and characterization of Getah virus in domestic pigs in Thailand, 2017-2018

Getah virus (GETV) is a mosquito-borne RNA virus belonging to the family Togaviridae, genus Alphavirus. GETV infection causes diarrhoea and death in piglets, and reproductive failure and abortion in sows. This study conducted a serological survey of GETV infection among domestic pig populations in Thailand. ELISA was used to analyse 1,188 pig serum samples collected from 11 provinces of Thailand during 2017-2018, with 23.1% of the samples being positive for anti-GETV antibodies. The positive ratio of anti-GETV antibodies was significantly higher in nursery (67.9%) and older stages (84.5%) of pigs than in finishing stage (14.2%). Furthermore, we successfully isolated GETV from one pig serum, designated as GETV strain GETV/SW/Thailand/2017, and determined the complete genome sequence (11,689 nt). Phylogenetic analysis demonstrated that our isolate was different from the recent GETV group spreading among pig populations in East Asia and formed a cluster with two GETV strains, namely YN12031 (China, 2015) and LEIV16275Mar (Far-East Russia, 2007). We concluded that two different GETV groups are currently spreading among pig populations in Asian countries.

A porcine epidemic diarrhea virus strain with distinct characteristics of four amino acid insertion in the COE region of spike protein

In recent years, a novel, highly virulent variant of porcine epidemic diarrhea virus (PEDV) has emerged, causing substantial economic losses to the pork industry worldwide. In this study, a PEDV strain named LNsy was successfully isolated in China. Phylogenetic analysis based on the whole genome revealed that PEDV LNsy belonged to the G2 subtype. For the first time, a unique four amino acids (4-aa) insertion was identified in the COE region of the spike (S) protein (residues 499-640), resulting in an extra alpha helix in the spatial structure of the COE region. To determine changes in virus-neutralization (VN) antibody reactivity of the virus, polyclonal antibodies (PAbs) against the S protein of different subtypes were used in a VN test. Both PAbs against the S protein of the G1 and G2 subtype showed reduced VN reactivity to PEDV LNsy. Further, recombination analyses revealed that PEDV LNsy was the result of recombination between PEDV GDS13 and GDS46 strains at the genomic breakpoints (nt 17,959-20,594 in the alignment) in the ORF1b gene of the genomes. Pathological examination showed gross morphological pathological changes in the gut, including significant villus atrophy and shedding of the infected piglets. These results indicated that a 4-aa insertion in the COE region of the S protein may have partly altered the profiles of VN antibodies and thus it will be important to develop vaccine candidates to resist wild virus infection and to monitor the genetic diversity of PEDV.

Abrogation of PRRSV infectivity by CRISPR-Cas13b-mediated viral RNA cleavage in mammalian cells

CRISPR/Cas9 enables dsDNA viral genome engineering. However, the lack of RNA targeting activities limits the ability of CRISPR/Cas9 to combat RNA viruses. The recently identified class II type VI CRISPR/Cas effectors (Cas13) are RNA-targeting CRISPR enzymes that enable RNA cleavage in mammalian and plant cells. We sought to knockdown the viral RNA of porcine reproductive and respiratory syndrome virus (PRRSV) directly by exploiting the CRISPR/Cas13b system. Effective mRNA cleavage by CRISPR/Cas13b-mediated CRISPR RNA (crRNA) targeting the ORF5 and ORF7 genes of PRRSV was observed. To address the need for uniform delivery of the Cas13b protein and crRNAs, an all-in-one system expressing Cas13b and duplexed crRNA cassettes was developed. Delivery of a single vector carrying double crRNAs enabled the simultaneous knockdown of two PRRSV genes. Transgenic MARC-145 cells stably expressing the Cas13b effector and crRNA mediated by lentiviral-based transduction showed a robust ability to splice the PRRSV genomic RNA and subgenomic RNAs; viral infection was almost completely abrogated by the combination of double crRNAs simultaneously targeting the ORF5 and ORF7 genes. Our study indicated that the CRISPR/Cas13b system can effectively knockdown the PRRSV genome in vitro and can potentially be used as a potent therapeutic antiviral strategy.

Enhancement of antigen-specific humoral immune responses and protein solubility through conjugation of bacterial flagellin, Vibrio vulnificus FlaB, to the N-terminus of porcine epidemic diarrhea virus surface protein antigen S0

Porcine epidemic diarrhea (PED) is a highly contagious enteric swine disease. The large economic impact of PED on the swine industry worldwide has made the development of an effective PED vaccine a necessity. S0, a truncated region of the porcine epidemic diarrhea virus (PEDV) spike protein, has been suggested as a candidate antigen for PED subunit vaccines; however, poor solubility problems when the protein is expressed in Escherichia coli, and the inherent problems of subunit vaccines, such as low immunogenicity, remain. Flagellin has been widely used as a fusion partner to enhance the immunogenicity and solubility of many difficult-to-express proteins; however, the conjugation effect of flagellin varies depending on the target antigen or the position of the fusion placement. Here, we conjugated flagellin, Vibrio vulnificus FlaB, to the N- and C-termini of S0 and evaluated the ability of the fusion to enhance the solubility and immunogenicity of S0. Flagellin conjugation in the presence of the trigger factor chaperone tig greatly improved the solubility of the fusion protein (up to 99%) regardless of its conjugation position. Of importance, flagellin conjugated to the N-terminus of S0 significantly enhanced S0-specific humoral immune responses compared to other recombinant antigens in Balb/c mice. The mechanism of this phenomenon was investigated through in vitro and in vivo studies. These findings provide important information for the development of a novel PED vaccine and flagellin-based immunotherapeutics.

A descriptive study of on-farm biosecurity and management practices during the incursion of porcine epidemic diarrhea into Canadian swine herds, 2014

Porcine epidemic diarrhea virus (PEDV) emerged into Canada in January 2014, primarily affecting sow herds. Subsequent epidemiological analyses suggested contaminated feed was the most likely transmission pathway. The primary objective of this study was to describe general biosecurity and management practices implemented in PEDV-positive sow herds and matched control herds at the time the virus emerged. The secondary objective was to determine if any of these general biosecurity and farm management practices were important in explaining PEDV infection status from January 22, 2014 to March 1, 2014. A case herd was defined as a swine herd with clinical signs and a positive test result for PEDV. A questionnaire was used to a gather 30-day history of herd management practices, animal movements on/off site, feed management practices, semen deliveries and biosecurity practices for case (n = 8) and control (n = 12) herds, primarily located in Ontario. Data was analyzed using descriptive statistics and random forests (RFs). Case herds were larger in size than control herds. Case herds had more animal movements and non-staff movements onto the site. Also, case herds had higher quantities of pigs delivered, feed deliveries and semen deliveries on-site. The biosecurity practices of case herds were considered more rigorous based on herd management, feed deliveries, transportation and truck driver practices than control herds. The RF model found that the most important variables for predicting herd status were related to herd size and feed management variables. Nonetheless, predictive accuracy of the final RF model was 72%.

Pathogenicity and immunogenicity of a new strain of porcine epidemic diarrhea virus containing a novel deletion in the N gene

Since late 2010, highly virulent PEDV G2-genotype strains have emerged globally extracting heavy losses on the pork industries of numerous countries. We investigated the characteristics of a field strain of PEDV (PEDV strain SH) isolated from a piglet with severe diarrhea on a farm in Shanghai China. Whole genome sequencing and analysis revealed that the SH strain belonged to subtype G2b and has a unique 12-aa deletion (aa 399-410) including the antigenic epitope NEP-1C9 (aa 398-406) of the N protein. PEDV SH strain is highly pathogenic to challenged newborn piglets, resulting in 100 % morbidity and mortality. Pathological examination revealed significant villus atrophy in the jejuna of infected piglets. Mice inoculated with inactivated PEDV SH produced antibodies against the N protein, but no antibodies against the deletions. These results illustrated that deletion of the NEP-1C9 epitope had no effect on the immunogenicity or pathogenicity of PEDV, providing evidence of the necessity to monitor the genetic diversity of the virus. Our study also contributes to development of candidate for vaccines and diagnostics that could differentiate pigs seropositive due to vaccination by conventional strains from wild virus infection.

Recombinant Chimeric Transmissible Gastroenteritis Virus (TGEV) - Porcine Epidemic Diarrhea Virus (PEDV) Virus Provides Protection against Virulent PEDV

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus causing high morbidity and mortality in porcine herds worldwide. Although both inactivated and live attenuated vaccines have been extensively used, the emergence of highly virulent strains and the recurrent outbreaks even in vaccinated farms highlight the need of effective vaccines. Engineering of genetically defined live attenuated vaccines is a rational approach for novel vaccine development. In this line, we engineered an attenuated virus based on the transmissible gastroenteritis virus (TGEV) genome, expressing a chimeric spike protein from a virulent United States (US) PEDV strain. This virus (rTGEV-RS-SPEDV) was attenuated in highly-sensitive five-day-old piglets, as infected animals did not lose weight and none of them died. In addition, the virus caused very minor tissue damage compared with a virulent virus. The rTGEV-RS-SPEDV vaccine candidate was also attenuated in three-week-old animals that were used to evaluate the protection conferred by this virus, compared with the protection induced by infection with a virulent PEDV US strain (PEDV-NVSL). The rTGEV-RS-SPEDV virus protected against challenge with a virulent PEDV strain, reducing challenge virus titers in jejunum and leading to undetectable challenge virus RNA levels in feces. The rTGEV-RS-SPEDV virus induced a humoral immune response specific for PEDV, including neutralizing antibodies. Altogether, the data indicated that rTGEV-RS-SPEDV is a promising vaccine candidate against virulent PEDV infection.

Decision-making in livestock biosecurity practices amidst environmental and social uncertainty: Evidence from an experimental game

Livestock industries are vulnerable to disease threats, which can cost billions of dollars and have substantial negative social ramifications. Losses are mitigated through increased use of disease-related biosecurity practices, making increased biosecurity an industry goal. Currently, there is no industry-wide standard for sharing information about disease incidence or on-site biosecurity strategies, resulting in uncertainty regarding disease prevalence and biosecurity strategies employed by industry stakeholders. Using an experimental simulation game, with primarily student participants, we examined willingness to invest in biosecurity when confronted with disease outbreak scenarios. We varied the scenarios by changing the information provided about 1) disease incidence and 2) biosecurity strategy or response by production facilities to the threat of disease. Here we show that willingness to invest in biosecurity increases with increased information about disease incidence, but decreases with increased information about biosecurity practices used by nearby facilities. Thus, the type or context of the uncertainty confronting the decision maker may be a major factor influencing behavior. Our findings suggest that policies and practices that encourage greater sharing of disease incidence information should have the greatest benefit for protecting herd health.

A newly isolated Chinese virulent genotype GIIb porcine epidemic diarrhea virus strain: Biological characteristics, pathogenicity and immune protective effects as an inactivated vaccine candidate

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A Chinese virulent genotype GIIb PEDV strain, CH/HNPJ/2017, was successfully separated and serially propagated in Vero cells.

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The biological characteristics and pathogenicity of PEDV strain CH/HNPJ/2017 were determined.

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The median pig diarrhea dose (PDD50) of Chinese PEDV strain was first determined.

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The immune protective effect of PEDV strain CH/HNPJ/2017 as vaccine candidates was also be evaluated.

Since October 2010, severe porcine epidemic diarrhea (PED) outbreaks caused by highly virulent PED virus (PEDV) strains have occurred continuously in the Chinese pig population and caused considerable economic losses. Although PEDV vaccines based on classical PEDV strains have been widely used in China in recent years, the morbidity and mortality in piglets remain high. Therefore, virulent genotype GII PEDV strains that are prevalent in the field should be isolated and used to develop next-generation vaccines. In the present study, a Chinese virulent genotype GIIb PEDV strain, CH/HNPJ/2017, was serially propagated in Vero cells for up to 90 passages. The S genes contained typical insertions and deletions that were also found in other recently isolated highly virulent PEDV strains from China and other countries and had two neighboring unique insertion mutations, which resulted in four amino acid changes in the S1 region of passages P10 and P60. Pig infection studies revealed that the CH/HNPJ/2017 strain was highly virulent in piglets, and the median pig diarrhea dose (PDD₅₀) was 7.68 log₁₀PDD₅₀/3 mL. Furthermore, the cell-adapted CH/HNPJ/2017 strain elicited potent serum IgG and neutralizing antibody responses in immunized pigs when it was used as an inactivated vaccine candidate. In addition, the pigs that received the experimental inactivated vaccines were partially protected (3/5) against subsequent viral challenge. In brief, these data indicate that the CH/HNPJ/2017 strain is a promising candidate for developing a safe and effective PEDV vaccine in the future.

A descriptive analysis of swine movements in Ontario (Canada) as a contributor to disease spread

In recent times, considerable efforts have been made to develop infrastructure and processes of tracing livestock movements. One of common use of this type of data is to assess the potential for spread of infections in source populations. The objectives of this research were to describe Ontario pig movements in 2015, and to understand the potential for disease transmission through animal movement on a weekly and yearly basis. Swine shipments from January to December 2015 represented 224 production facilities and a total of 5398 unique animal movements. This one-mode directed network of animal movements was then analyzed using common descriptive network measures. The maximum yearly (_y) weak component (WC_y) size and maximum weekly (_w) weak component size (WC_w) was 224 facilities, and 83 facilities, respectively. The maximum WC_w did not change significantly (p > 0.05) over time. The maximum strong component (SC) consisted of two facilities both on a weekly, and on a yearly basis. The size of the maximum ingoing contact chain on a yearly basis (ICC_y) was 173 nodes with one abattoir as the end point, and the maximum ICC_w consisted of 53 nodes. The size of the maximum outgoing contact chain (OCC_y) contained 79 nodes, with one sow herd as a starting point. The maximum OCC_w was 6 nodes. Regression models resulted in significant quadratic associations between weekly count of finisher facilities with betweenness >0 (p = 0.02) and weekly count of finisher facilities with in-degree and out-degree >0 (p = 0.01) and week number. Higher weekly counts of nursery and finisher facilities with betweenness >0 and in-degree and out-degree both >0 values occurred during summer months. All study facilities were connected when direction of animal movement was not taken into consideration in the yearly network. As such, yearly networks are potentially representative of infections with long incubation periods, subclinical infections, or endemic infections for which active control measures have not being taken. When the direction of animal movement was considered, such infection could still spread substantially and affect 35% of the study population (79/224). In the study population, finisher sites were proportionally and consistently most represented in WC_w (min = 51%, max = 78%), which reflects current Ontario herd demographics. However, abattoirs were over-represented when the number of facilities in the study population was taken into consideration. This, and the size of the maximum ICC_w both suggest that abattoirs could be, at least for some infectious diseases, suitable establishments for targeted sampling.

Efficacy of a type 2 PRRSV modified live vaccine (PrimePac™ PRRS) against a Thai HP-PRRSV challenge

The Chinese highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) has caused a severe threat to the pig population in Southeast Asian countries. The purpose of this study was to investigate the efficacy of a type 2 PRRSV modified live vaccine (PrimePac™ PRRS, lineage 7) against a Thai HP-PRRSV (10PL01, lineage 8). Three-week-old PRRSV-free pigs were randomly assigned into three groups. Vaccinated challenged group (group 1, n = 16) was immunized with PrimePac™ PRRS vaccine at 3 weeks old. The unvaccinated challenged group (group 2, n = 16) was injected with PBS at 3 weeks old, and unvaccinated unchallenged group (group 3, n = 10) was served as a negative control. At 9 weeks old, all groups, except the negative control group, were challenged with the Thai HP-PRRSV. All pigs were monitored daily during 10 days post-infection (dpi) and were necropsied at 10 and 17 dpi. The results revealed that vaccinated challenged pigs showed significantly lower (p < 0.05) mean rectal temperatures, clinical respiratory scores, lung lesion scores, and levels of virus load in serum and lung tissue compared with the unvaccinated challenged pigs. Moreover, vaccinated challenged pigs exhibited PRRSV-specific serum neutralizing antibodies at the end of the experiment. Our findings indicated that the studied type 2 PRRSV vaccine provided partial protection against the Thai HP-PRRSV infection based on the body temperature, levels of viremia, and the severity of lung lesions. These results demonstrated that partial protection of PrimePac™ PRRS vaccine might be useful for controlling HP-PRRSV infection in the endemic area.

A new and efficient culture method for porcine bone marrow-derived M1- and M2-polarized macrophages

BACKGROUND

Macrophages play an important role in the innate immune system as part of the mononuclear phagocyte system (MPS). They have a pro-inflammatory signature (M1-polarized macrophages) or anti-inflammatory signature (M2-polarized macrophages) based on expression of surface receptors and secretion of cytokines. However, very little is known about the culture of macrophages from pigs and more specific about the M1 and M2 polarization in vitro.

METHODS

Porcine monocytes or mononuclear bone marrow cells were used to culture M1- and M2-polarized macrophages in the presence of GM-CSF and M-CSF, respectively. Surface receptor expression was measured with flow cytometry and ELISA was used to quantify cytokine secretion in response to LPS and PAM₃CSK₄ stimulation. Human monocyte-derived macrophages were used as control.

RESULTS

Porcine M1- and M2-polarized macrophages were cultured best using porcine GM-CSF and murine M-CSF, respectively. Cultures from bone marrow cells resulted in a higher yield M1- and M2-polarized macrophages which were better comparable to human monocyte-derived macrophages than cultures from porcine monocytes. Porcine M1-polarized macrophages displayed the characteristic fried egg shape morphology, lower CD163 expression and low IL-10 production. Porcine M2-polarized macrophages contained the spindle-like morphology, higher CD163 expression and high IL-10 production.

CONCLUSION

Porcine M1- and M2-polarized macrophages can be most efficiently cultured from mononuclear bone marrow cells using porcine GM-CSF and murine M-CSF. The new culture method facilitates more refined studies of porcine macrophages in vitro, important for both porcine and human health since pigs are increasingly used as model for translational research.

Inferring the evolution of the major histocompatibility complex of wild pigs and peccaries using hybridisation DNA capture-based sequencing

The major histocompatibility complex (MHC) is a key genomic model region for understanding the evolution of gene families and the co-evolution between host and pathogen. To date, MHC studies have mostly focused on species from major vertebrate lineages. The evolution of MHC classical (Ia) and non-classical (Ib) genes in pigs has attracted interest because of their antigen presentation roles as part of the adaptive immune system. The pig family Suidae comprises over 18 extant species (mostly wild), but only the domestic pig has been extensively sequenced and annotated. To address this, we used a DNA-capture approach, with probes designed from the domestic pig genome, to generate MHC data for 11 wild species of pigs and their closest living family, Tayassuidae. The approach showed good efficiency for wild pigs (~80% reads mapped, ~87× coverage), compared to tayassuids (~12% reads mapped, ~4× coverage). We retrieved 145 MHC loci across both families. Phylogenetic analyses show that the class Ia and Ib genes underwent multiple duplications and diversifications before suids and tayassuids diverged from their common ancestor. The histocompatibility genes mostly form orthologous groups and there is genetic differentiation for most of these genes between Eurasian and sub-Saharan African wild pigs. Tests of selection showed that the peptide-binding region of class Ib genes was under positive selection. These findings contribute to better understanding of the evolutionary history of the MHC, specifically, the class I genes, and provide useful data for investigating the immune response of wild populations against pathogens.

Interleukin-1 receptor antagonist: an early immunomodulatory cytokine induced by porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) infection poorly induces pro-inflammatory cytokines (IL-1, IL-6 and TNF-α) and type I IFN production during the early phase of infection. Our microarray analysis indicated strong upregulation of the IL1RA gene in type 2 PRRSV -infected monocyte-derived dendritic cells. Interleukin-1 receptor antagonist (IL-1Ra) is an early inhibitory cytokine that suppresses pro-inflammatory cytokines and T-lymphocyte responses. To investigate the induction of IL-1Ra by PRRSV, monocyte-derived dendritic cells were cultured with type 2 PRRSV or other swine viruses. PRRSV increased both IL1RA gene expression and IL-1Ra protein production in the culture. The enhanced production of IL-1Ra was further confirmed in PRRSV-cultured PBMC and PRRSV-exposed pigs by flow cytometry. Myeloid cell population appeared to be the major IL-1Ra producer both in vitro and in vivo. In contrast to the type 2 PRRSV, the highly pathogenic (HP)- PRRSV did not upregulate IL1RA gene expression in vitro. To determine the kinetics of PRRSV-induced IL1RA gene expression in relation to other pro-inflammatory cytokine genes, PRRSV-negative pigs were vaccinated with a commercially available type 2 modified-live PRRS vaccine or intranasally inoculated with HP-PRRSV. In modified-live PRRS vaccine pigs, upregulation of IL1RA, but not IL1B and IFNA, gene expression was observed from 2 days post- vaccination. Consistent with the in vitro findings, upregulation of IL1RA gene expression was not observed in the HP-PRRSV-infected pigs throughout the experiment. This study identified IL-1Ra as an early immunomodulatory mediator that could be involved in the immunopathogenesis of PRRSV infections.

Porcine epidemic diarrhea in China

Porcine epidemic diarrhea (PED) is a contagious intestinal disease caused by Porcine epidemic diarrhea virus (PEDV) that characterized by vomiting, diarrhea, and dehydration. PEDV was first identified in the 1980s in China, and since then, it has become one of the most common viral causes of diarrhea. In October 2010, a large-scale outbreak of PED caused by a PEDV variant occurred in China, resulting in tremendous economic losses. This review presents a comprehensive description of PEDV history, prevalence, molecular features, and prevention and control strategies in China.

Positive immunomodulatory effects of heterologous DNA vaccine- modified live vaccine, prime-boost immunization, against the highly-pathogenic PRRSV infection

Porcine reproductive and respiratory syndrome virus (PRRSV) infection is one of the most important swine pathogens, and causes a major economic impact worldwide. Recently, a new variant type 2 PRRSV, highly pathogenic PRRSV (HP-PRRSV) has emerged and continued to circulate in Southeast Asia region. Currently, commercially available PRRSV vaccines, modified live PRRS vaccines (MLV) are not able to provide complete protection against HP-PRRSV and been reported to induce negative immunomodulatory effects. Interestingly, a novel DNA vaccine was developed and successfully used to improve PRRSV-specific immune responses following MLV vaccination. To investigate the efficacy of a heterologous DNA-MLV prime-boost immunization against the HP-PRRSV infection, an experimental vaccinated-challenged study was conducted. Two-week-old, PRRSV-seronegative, crossbred pigs (5-8 pigs/group) were allocated into 5 groups. At day -14 (D-14), the treatment group (DNA-MLV) was immunized with a DNA vaccine encoding PRRSV-truncated nucleocapsid protein (pORF7t), followed by a commercial modified live type 2 PRRS vaccine (MLV) at D0. The other groups included the group that received PBS at D-14 followed by MLV at D0 (MLV), pORF7t at D-14 (DNA), PBS at D0 (PBS) and the negative control group. At D42, all groups, except the negative control group, were challenged with HP-PRRSV (strain 10PL1). The results demonstrated that pigs that received MLV, regardless of the DNA priming, exhibited less clinical signs and faster viral clearance. Following HP-PRRSV challenge, the DNA-MLV group exhibited improved PRRSV-specific immunity, as observed by increased neutralizing antibody titers and PRRSV-specific IFN-γ production, and reduced IL-10 and PRRSV-specific Treg productions. However, neither the prime-boost immunization nor the MLV was able to induce complete clinical protection against HP-PRRSV infection. In conclusion, improved immunological responses, but not clinical protection, were achieved by DNA-MLV prime-boost immunization. This study highlights the potential use of heterologous prime-boost vaccination regimen, where DNA can be incorporated with other vaccine candidates, for improving anti-PRRSV immunity that may eventually lead induction of complete PRRSV protection.

Efficacy of Fostera® PRRS modified live virus (MLV) vaccination strategy against a Thai highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) infection

Recently, the Chinese highly pathogenic porcine reproductive and respiratory syndrome virus (PRRSV) (HP-PRRSV) belonging to lineage 8 causes severe symptom with high morbidity and high mortality rates to the Asian pig industry. A recent study showed that pigs immunized with Fostera® PRRS modified live virus (MLV) of lineage 8 could provide a degree of protection against a Vietnamese HP-PRRSV infection. It should be noted that PRRSV commonly found after weaning causes porcine respiratory disease complex (PRDC). Vaccination strategy should be evaluated in each farm scenario. Eighty-one PRRSV-free piglets obtained from a PRRS-free herd were divided into two experiments with the major difference of infection timing after vaccination, 42 days in experiment 1 (n = 42) and 28 days in experiment 2 (n = 39). Each experiment had similar protocol containing three groups including a negative control, unvaccinated challenged, and vaccinated challenged groups. Pigs in vaccination groups were immunized with Fostera® PRRS MLV vaccine at 3 weeks of age. Then, unvaccinated challenged and vaccinated challenged groups were intranasally inoculated with a Thai HP-PRRSV (10PL01). Vaccinated challenged pigs showed significantly lower levels of mean rectal temperatures, clinical severity, lung lesion scores, and viral titers in serum and lung tissue compared to the unvaccinated challenged pigs (p < 0.05). Vaccinated challenged pigs had higher survival rate than those of unvaccinated challenged pigs in both experiments. It should be noted that pigs challenged 42 days after vaccination showed a better performance than pigs challenged 28 days after vaccination. In conclusion, Fostera® PRRS MLV vaccine was able to improve the survival rate against the Thai HP-PRRSV infection in both 42- and 28-day vaccination-to-infection protocols.

The dilemma of rare events: Porcine epidemic diarrhea virus in North America

Porcine epidemic diarrhea virus (PEDV) has been recognized as a swine pathogen for 40 years, but until 2013 had not been detected in the Western Hemisphere. From originally causing a relatively mild and sporadic disease, PEDV has been more recently associated with severe outbreaks of diarrheal disease in Asia, and subsequently North America. PEDV shares some important characteristics with two major pandemic viruses (porcine reproductive and respiratory virus; porcine circovirus type 2) of pigs that have high rates of mutation and high host specificity, and appear to have been present in the swine virome for decades prior to emerging to cause severe clinical disease. A unique feature of the PEDV in North America has been the implication of feed as a vehicle for transmission, with particular concerns related to ingredients of porcine origin. The importance of relatively rare events in contributing to both the emergence and transmission of PEDV is discussed in relation to approaches for managing the associated risks.

Porcine epidemic diarrhea: a review of current epidemiology and available vaccines

Porcine epidemic diarrhea virus (PEDV), an Alphacoronavirus in the family Coronaviridae, causes acute diarrhea, vomiting, dehydration, and high mortality rates in neonatal piglets. PEDV can also cause diarrhea, agalactia, and abnormal reproductive cycles in pregnant sows. Although PEDV was first identified in Europe, it has resulted in significant economic losses in many Asian swine-raising countries, including Korea, China, Japan, Vietnam, and the Philippines. However, from April 2013 to the present, major outbreaks of PEDV have been reported in the United States, Canada, and Mexico. Moreover, intercontinental transmission of PEDV has increased mortality rates in seronegative neonatal piglets, resulting in 10% loss of the US pig population. The emergence and re-emergence of PEDV indicates that the virus is able to evade current vaccine strategies. Continuous emergence of multiple mutant strains from several regions has aggravated porcine epidemic diarrhea endemic conditions and highlighted the need for new vaccines based on the current circulating PEDV. Epidemic PEDV strains tend to be more pathogenic and cause increased death in pigs, thereby causing substantial financial losses for swine producers. In this review, we described the epidemiology of PEDV in several countries and present molecular characterization of current strains. We also discuss PEDV vaccines and related issues.

Comparison of serum and oral fluid antibody responses after vaccination with a modified live (MLV) porcine reproductive and respiratory syndrome virus (PPRSV) vaccine in PRRS endemic farms

Porcine reproductive and respiratory syndrome (PRRS) is a disease that is both highly contagious and of great economic importance in Malaysia. Therefore, reliable and improved diagnostic methods are needed to facilitate disease surveillance. This study compared PRRSV antibody responses in oral fluid versus serum samples following PRRS modified live (MLV) vaccination using commercial antibody ELISA kits (IDEXX Laboratories, Inc.). The study involved two pig farms located in Perak and Selangor, Malaysia. Both farms were vaccinated with PRRS MLV 1 month prior to sample collection. Thirty-five animals were used as subjects in each farm. These 35 animals were divided into 7 different categories: gilts, young sows, old sows, and four weaner groups. Oral fluid and serum samples were collected from these animals individually. In addition, pen oral fluid samples were collected from weaner groups. The oral fluid and serum samples were tested with IDEXX PRRS Oral Fluid Antibody Test Kit and IDEXX PRRS X3 Antibody Test Kit, respectively. The results were based on sample to positive ratio (S/P ratio of the samples). Results revealed a significant and positive correlation between serum and oral fluid samples for both farm A (p = 0.0001, r = 0.681) and farm B (p = 0.0001, r = 0.601). In general, oral fluids provided higher S/P results than serum, but the patterns of response were highly similar, especially for the sow groups. Thus, the use of oral fluids in endemic farms is effective and economical, particularly for large herds. In conclusion, the authors strongly recommend the use of oral fluids for PRRS monitoring in endemic farms.

Scientific Opinion on porcine epidemic diarrhoea and emerging porcine deltacoronavirus

In the last decade, many porcine epidemic diarrhoea (PED) outbreaks have been reported by several countries in Asia whereas only a few Member States of the European Union (EU) have reported PED clinical cases and/or PED virus (PEDV)-seropositive animals. This alphacoronavirus was first reported in the USA in May 2013, followed by rapid spread throughout the country and outbreaks reported by several countries in the Americas. The recent PEDV-EU isolates have high level of sequence identity to PEDV-Am isolates. Based on nucleotide sequencing, multiple variants of PEDV are circulating in Europe, the Americas and Asia but any difference in virulence and antigenicity is currently unknown. Serological cross-reactivity has been reported between PEDV isolated in Europe and in the Americas; however no data regarding cross-protection are available. The impact of different PEDV strains is difficult to compare between one country and another, since impact is dependent not only on pathogenicity but also on factors such as biosecurity, farm management, sanitary status or herd immune status. However, the clinical signs of PEDV infections in naive pigs are similar in different countries with mortalities up to 100% in naive newborn piglets. The impact of recently reported PED outbreaks in Asia and the USA seems to be more severe than what has been described in Europe. Infected animals, faeces, feed and objects contaminated with faeces are matrices that have been reported to transmit PEDV between farms. Infectious PEDV has been detected in spray-dried porcine plasma (SDPP) in one study but the origin of the infectious PEDV in SDPP is not clear. Detection of porcine deltacoronavirus (PDCoV) has been reported in a few countries but only limited testing has been done. Based on the currently available information, it seems that PDCoV would have a lower impact than PEDV.