Virus Infection In Pigs Research Articles

Clinical and pathologic characterization of African swine fever virus infection in pigs in the Mekong Delta, Vietnam

African swine fever (ASF) is a highly infectious disease in pigs caused by the African swine fever virus (ASFV), which might result in 100% mortality. Pigs infected with ASFV might display different clinical and pathological features depending on virulence and host factors. This study aimed to determine features of clinical symptoms, macroscopic, and microscopic lesions of ASF in the Mekong Delta (MD), Vietnam during 2021–2022. The investigation was conducted following three fatal outbreaks of ASF in Hau Giang, Vinh Long, and Can Tho provinces, which are three central provinces out of thirteen in the MD. The spleen, lymph nodes, liver, kidney, and heart were collected from three infected pigs that displayed clinical symptoms of ASFV infection and confirmed the presence of ASFV by conventional PCR. The results indicated that infected pigs showed common clinical symptoms including high fever, anorexia, and moderate petechiae on the skin. Severe hemorrhage was observed in lymph nodes, spleen, kidneys, intestines, and gallbladders which were the main lesions during post-mortem examination. Microscopic lesions were characterized by lymphocytopenia, atrophy of lymphoid follicles in the immune system. However, distinct variations in clinical symptoms, macroscopic, and microscopic features among ASFV infection cases were not documented. This study provides a further understanding of the clinical presentation and pathological lesions caused by the ASFV strain circulating in the MD.

Gene editing of pigs to control influenza A virus infections

ABSTRACT Proteolytic activation of the haemagglutinin (HA) glycoprotein by host cellular proteases is pivotal for influenza A virus (IAV) infectivity. Highly pathogenic avian influenza viruses possess the multibasic cleavage site of the HA which is cleaved by ubiquitous proteases, such as furin; in contrast, the monobasic HA motif is recognized and activated by trypsin-like proteases, such as the transmembrane serine protease 2 (TMPRSS2). Here, we aimed to determine the effects of TMPRSS2 on the replication of pandemic H1N1 and H3N2 subtype IAVs in the natural host, the pig. The use of the CRISPR/Cas 9 system led to the establishment of homozygous gene edited (GE) TMPRSS2 knockout (KO) pigs. Delayed IAV replication was demonstrated in primary respiratory cells of KO pigs in vitro. IAV infection in vivo resulted in a significant reduction of virus shedding in the upper respiratory tract, and lower virus titers and pathological lesions in the lower respiratory tract of TMPRSS2 KO pigs as compared to wild-type pigs. Our findings support the commercial use of GE pigs to mitigate influenza A virus infection in pigs, as an alternative approach to prevent zoonotic influenza A transmissions from pigs to humans.

Exosomal ssc-miR-1343 targets FAM131C to regulate porcine epidemic diarrhea virus infection in pigs

The porcine epidemic diarrhea virus (PEDV) causes diarrhea in piglets, thereby causing very significant economic losses for the global swine industry. In previous studies, it has been confirmed that microRNAs (miRNAs) play an important role in the infection caused by PEDV. However, the precise molecular mechanism of miRNAs in the regulation of PEDV infection is still not fully understood. In the present study, we utilized miRNA-seq analysis to identify ssc-miR-1343 with differential expression between PEDV-infected and normal piglets. The expression of ssc-miR-1343 was detected in isolated exosomes, and it was found to be significantly higher than that in the controls following PEDV infection. The ssc-miR-1343 mimic was found to decrease PEDV replication, whereas the ssc-miR-1343 inhibitor was observed to increase PEDV replication, and ssc-miR-1343 was delivered by exosomes during PEDV infection. Mechanistically, ssc-miR-1343 binds to the 3′UTR region of FAM131C, down-regulating its expression, and FAM131C has been shown to enhance PEDV replication through simultaneously suppressing pathways associated with innate immunity. The ssc-miR-1343/FAM131C axis was found to upregulate the host immune response against PEDV infection. In conclusion, our findings indicate that the transport of ssc-miR-1343 in exosomes is involved in PEDV infection. This discovery presents a new potential target for the development of drugs to treat PEDV.

Dysfunction of Complementarity Determining Region 1 Encoded by T Cell Receptor Beta Variable Gene Is Potentially Associated with African Swine Fever Virus Infection in Pigs.

The beta T-cell receptor (TRB) expressed by beta T cells is essential for foreign antigen recognition. The TRB locus contains a TRBV family that encodes three complementarity determining regions (CDRs). CDR1 is associated with antigen recognition and interactions with MHC molecules. In contrast to domestic pigs, African suids lack a 284-bp segment spanning exons 1 and 2 of the TRBV27 gene that contains a sequence encoding CDR1. In this study, we used the African swine fever virus (ASFV) as an example to investigate the effect of deleting the TRBV27-encoded CDR1 on the resistance of domestic pigs to exotic pathogens. We first successfully generated TRBV27-edited fibroblasts with disruption of the CDR1 sequence using CRISPR/Cas9 technology and used them as donor cells to generate gene-edited pigs via somatic cell nuclear transfer. The TRBV-edited and wild-type pigs were selected for synchronous ASFV infection. White blood cells were significantly reduced in the genetically modified pigs before ASFV infection. The genetically modified and wild-type pigs were susceptible to ASFV and exhibited typical fevers (>40 °C). However, the TRBV27-edited pigs had a higher viral load than the wild-type pigs. Consistent with this, the gene-edited pigs showed more clinical signs than the wild-type pigs. In addition, both groups of pigs died within 10 days and showed similar severe lesions in organs and tissues. Future studies using lower virulence ASFV isolates are needed to determine the relationship between the TRBV27 gene and ASFV infection in pigs over a relatively long period.

Bacillus subtilis-597 induces changes in lung pathology and inflammation during influenza A virus infection in pigs

In recent years, it has become apparent that imbalances in the gastrointestinal system can impact organs beyond the intestine such as the lungs. Given the established ability of probiotics to modulate the immune system by interacting with gastrointestinal cells, our research aimed to investigate whether administering the probiotic strain Bacillus subtilis-597 could mitigate the outcome of influenza virus infection in pigs. Pigs were fed a diet either with or without the probiotic strain B. subtilis-597 for 14 days before being intranasally inoculated with a swine influenza A H1N2 strain (1 C.2 lineage). Throughout the study, we collected fecal samples, blood samples, and nasal swabs to examine viral shedding and immune gene expression. After seven days of infection, the pigs were euthanized, and lung and ileum tissues were collected for gene expression analysis and pathological examination. Our findings indicate that the administration of B. subtilis-597 exhibit potential in reducing lung lesions, possibly attributable to a general suppression of the immune system as indicated by reduced C-reactive protein (CRP) levels in serum, decreased expression of interferon-stimulated genes (ISGs), and localized reduction of the inflammatory marker serum amyloid A (SAA) in ileum tissue. Notably, the immune-modulatory effects of B. subtilis-597 appeared to be unrelated to the gastrointestinal microbiota, as the composition remained unaltered by both the influenza infection and the administration of B. subtilis-597.

Hematological and serum biochemical profiles of a natural African swine fever virus infection in pigs.

African swine fever (ASF) is a contagious viral disease that affects pigs of all ages, inducing hemorrhagic fever with high mortality and severe threat to pig production. This study investigated the hematological and serum biochemical abnormalities associated with a natural ASF infection in pigs. A total of 100 serum samples of pigs from piggery suspected of ASFV infection were screened for antibodies by ELISA. Thirty‑two blood samples from serologically positive pigs and 32 negative pigs were undergo to hematological and serum biochemical analyses following standard procedures. The results showed that the mean values of the red blood cell (RBC) count, total white blood cell (TWBC) count, absolute lymphocyte count, absolute monocyte count, serum total protein (TP) and globulin were significantly (p < 0.05) lower while the mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), absolute neutrophil count and serum gamma glutamyl transferase (GGT) were significantly (p < 0.05) higher in the infected than the healthy pigs. There were no significant differences (p > 0.05) in the mean values of the packed cell volume (PCV), hemoglobin concentration, absolute eosinophil count, cholesterol, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities between the infected and healthy pigs. Hence, natural ASFV infection may have caused alterations in the hematological and serum biochemical parameters in the infected pigs. The generated data could complement the existing laboratory diagnostic techniques such as polymerase chain reaction, direct fluorescence antibody test, indirect fluorescent antibody test and ELISA in the diagnosis of ASF in pigs.

High prevalence of acute hepatitis E virus infection in pigs in Dutch slaughterhouses

Hepatitis E is caused by hepatitis E virus (HEV), one of the causes of acute viral hepatitis. Domestic pigs are considered as the main reservoir of HEV-3. The recently reported high prevalence of HEV in liver- and meat products on the Dutch market warranted a cross-sectional prevalence study on HEV infection among 5–6 months old pigs slaughtered in the Netherlands (n = 250). For this, liver, caecum content and blood samples were analyzed for the presence of genomic HEV RNA by RT-PCR. In addition, a serological test was performed to detect HEV IgG. Background information was retrieved on the corresponding farms to evaluate potential risk factors for HEV at pig slaughter age.HEV IgG was detected in sera from 167 pigs (67.6 %). HEV RNA was detected in 64 (25.6 %) caecum content samples, in 40 (16.1 %) serum samples and in 25 (11.0 %) liver samples. The average level of viral contamination in positive samples was log10 4.6 genome copies (gc)/g (range 3.0–8.2) in caecum content, log10 3.3 gc/ml (range 2.4–5.9) in serum and log10 3.2 gc/0.1 g (range 1.7–6.2) in liver samples. Sequence analyses revealed HEV-3c only. Ten times an identical strain was detected in two or three samples obtained from the same pig. Each animal in this study however appeared to be infected with a unique strain. The presence of sows and gilts and welfare rating at the farm of origin had a significant effect (p < 0.05) on the distribution over the four groups representing different stages of HEV infection based on IgG or RNA in caecum and/or serum. The observed proportion of tested pigs with viremia (16 %) was higher than in other reported studies and was interestingly often observed in combination with a high number of HEV genome copies in liver and caecum content as detected by RT-qPCR. Data provided will be useful for risk assessment for food safety of pork products, will provide baseline data for future monitoring of HEV infections in pigs and new thoughts for mitigation strategies.

Cross-Species Transmission of Rabbit Hepatitis E Virus to Pigs and Evaluation of the Protection of a Virus-like Particle Vaccine against Rabbit Hepatitis E Virus Infection in Pigs.

We investigated the cross-species transmission of rabbit hepatitis E virus (rb HEV) to pigs and evaluated the cross-protection of a swine (sw) HEV-3 virus-like particle (VLP) vaccine against rb HEV infection in pigs. Twelve 4-week-old conventional pigs were divided into negative control (n = 3), positive control (rb HEV-infected, n = 4), and vaccinated (vaccinated and rb HEV-challenged, n = 5) groups. The vaccine was administered at weeks 0 and 2, and viral challenge was conducted at week 4. Serum HEV RNA, anti-HEV antibody, cytokine, and liver enzyme levels were determined. Histopathological lesions were examined in abdominal organs. Viral RNA was detected and increased anti-HEV antibody and alanine aminotransferase (ALT) levels were observed in positive control pigs; liver fibrosis, inflammatory cell infiltration in the lamina propria of the small intestine and shortened small intestine villi were also observed. In vaccinated pigs, anti-HEV antibody and Th1 cytokine level elevations were observed after the second vaccination; viral RNA was not detected, and ALT level elevations were not observed. The results verified the cross-species transmission of rb HEV to pigs and cross-protection of the sw HEV-3 VLP vaccine against rb HEV infection in pigs. This vaccine may be used for cross-protection against HEV infection in other species.

Prevalence of Bovine Viral Diarrhea Virus Infections in Pigs on Jeju Island, South Korea, from 2009-2019 and Experimental Infection of Pigs with BVDV Strains Isolated from Cattle.

On Jeju Island, South Korea, pigs have not been vaccinated against classical swine fever (CSF) since 1999. Analysis of bovine viral diarrhea virus (BVDV) isolated from pigs on Jeju Island between 2009 and 2019 identified five BVDV-1a strains and one BVDV-1b strain. These BVDV types were shown to be the same types as BVDV strains isolated from neighboring cow farms. BVDV antibody-positive pigs (both BVDV-1 and -2) were also detected at 54 of 168 pig farms during this period. In pig infection experiments using BVDV-1a and -2a strains isolated from neighboring cow farms, BVDV-1a was detected in the blood of one of four pigs infected at both 6 and 35 days post-infection (dpi) and in the blood of two of the four pigs at 28 dpi. Pigs showed higher anti-BVDV-1 titers (5.5 ± 1.5 log2) at 35 dpi. BVDV-2a was detected in the blood of one of four pigs infected with this virus at 28 dpi only, and lower antibody titers (2.75 ± 0.75 log2) were seen in these pigs at 35 dpi. While BVDV infection is not particularly pathogenic in pigs, it is still important to monitor porcine BVDV infections due to a differential diagnosis of CSFV.

Survey of Japanese encephalitis reactor on pigs in north Sulawesi

Several studies have shown that pigs are considered as the main reservoir of Japanese encephalitis virus transmission in Indonesia, in addition to having isolated Japanese encephalitis virus in pigs, pigs are also the type of livestock that is most often reported to contain Japanese encephalitis antibodies with a relatively high infection rate. This study aims to determine the spread and magnitude of Japanese encephalitis virus infection in pigs by detecting the presence of Japanese encephalitis antibodies using the Competitive Enzyme Linked Immuno Assay (C-ELISA). By knowing the spread of Japanese encephalitis virus infection in pigs in North Sulawesi Province, it can indirectly be used as an indicator of the possible threat of Japanese encephalitis virus transmission to humans, especially if the location of pig farms is close to residential areas. The results of serological examination using the Competitive ELISA method on 50 samples of porcine serum in 3 districts/cities, 30% of Japanese encephalitis reactors (15 samples were positive). The JE reactor in pigs in Minahasa Regency is the highest (43.8%) compared to Tomohon City (29.4%) and South Minahasa Regency (17.6%). The proximity of pigs to humans can be seen from the location of the settlements adjacent to the location of pig farms. Pigs located in Minahasa Regency which are close to settlements are the highest risk factors for the transmission of the Japanese Encephalitis virus.

Serological evidence of hepatitis E virus infection in pigs from Northern Bulgaria.

The purpose of the present study was to investigate pigs in Northern Bulgaria for serological evidence of hepatitis E virus (HEV). Sera from 225 individuals from three industrial farms were tested for anti‑HEV IgG antibodies. The overall HEV seroprevalence was 36% (81/225); weaners 6.8% (5/74); fattening pigs 38.7% (29/75) and in sows 61.8% (47/76). Compared to weaners, HEV positivity was higher in fattening pigs and sows: OR = 8.70 (95% CI: 3.14‑24.12) and OR = 22.37 (95% CI: 8.07‑61.96), respectively. These data confirm that HEV is endemic in pigs throughout Bulgaria, and can be a Public Health problem due to the transmission of HЕV to humans through the consumption of pork meat and pork products.

Immune Responses to Pandemic H1N1 Influenza Virus Infection in Pigs Vaccinated with a Conserved Hemagglutinin HA1 Peptide Adjuvanted with CAF®01 or CDA/αGalCerMPEG.

This study aimed to evaluate the immune response and protection correlates against influenza virus (IV) infection in pigs vaccinated with the novel NG34 HA1 vaccine candidate adjuvanted with either CAF®01 or CDA/αGalCerMPEG (αGCM). Two groups of six pigs each were vaccinated intramuscularly twice with either NG34 + CAF®01 or NG34 + CDA/αGCM. As controls, groups of animals (n = 6 or 4) either non-vaccinated or vaccinated with human seasonal trivalent influenza vaccine or NG34 + Freund’s adjuvant were included in the study. All animal groups were challenged with the 2009 pandemic (pdm09) strain of H1N1 (total amount of 7 × 106 TCID50/mL) via intranasal and endotracheal routes 21 days after second vaccination. Reduced consolidated lung lesions were observed both on days three and seven post-challenge in the animals vaccinated with NG34 + CAF®01, whereas higher variability with relatively more severe lesions in pigs of the NG34 + CDA/αGCM group on day three post-infection. Among groups, animals vaccinated with NG34 + CDA/αGCM showed higher viral loads in the lung at seven days post infection whereas animals from NG34 + CAF®01 completely abolished virus from the lower respiratory tract. Similarly, higher IFNγ secretion and stronger IgG responses against the NG34 peptide in sera was observed in animals from the NG34 + CAF®01 group as compared to the NG34 + CDA/αGCM. NG34-vaccinated pigs with adjuvanted CAF®01 or CDA/αGCM combinations resulted in different immune responses as well as outcomes in pathology and viral shedding.

Risk and Mitigation of African Swine Fever Virus in Feed.

Simple SummaryAfrican swine fever is the most significant disease threat to swine globally, and recent introductions into previously negative countries has heightened the risk for disease spread. Without an effective vaccine or treatment, the primary objective of negative countries is to prevent African swine fever virus infection in pigs. Significant quantities of feed ingredients used for swine diets are traded worldwide and may be imported from countries with African swine fever. If feed ingredients are contaminated with the virus, they can serve as potential routes for the introduction and transmission of African swine fever virus. This review provides information on the risk of African swine fever virus in feed and the mitigation strategies that may help protect the global swine population from introduction and spread through feed.Since the 2013 introduction of porcine epidemic diarrhea virus into the United States (U.S.), feed and feed ingredients have been recognized as potential routes for the introduction and transmission of foreign animal diseases of swine. Feed ingredients for swine diets are commodities traded worldwide, and the U.S. imports thousands of metric tons of feed ingredients each year from countries with circulating foreign animal diseases. African swine fever (ASF) is the most significant foreign animal disease threat to U.S. swine production, and the recent introduction of ASF into historically negative countries has heightened the risk for further spread. Laboratory investigations have characterized the stability of the ASF virus (ASFV) in feed ingredients subjected to transoceanic shipment conditions, ASFV transmissibility through the natural consumption of plant-based feed, and the mitigation potential of certain feed additives to inactivate ASFV in feed. This review describes the current knowledge of feed as a risk for swine viruses and the opportunities for mitigating the risk to protect U.S. pork production and the global swine population from ASF and other foreign animal diseases.

Evidence of Zika Virus Infection in Pigs and Mosquitoes, Mexico.

Evidence suggests that pigs seroconvert after experimental exposure to Zika virus and are potential sentinels. We demonstrate that pigs are also susceptible to natural Zika virus infection, shown by the presence of antibodies in domestic pigs in Yucatan, Mexico. Zika virus RNA was detected in 5 species of mosquitoes collected inside pigpens.

Preliminary screening of intestinal barrier genes associated with porcine epidemic diarrhea virus infection in pigs

To screen intestinal barrier genes associated with porcine epidemic diarrhea virus (PEDV) infection, in the present study we first detected PEDV-infected piglets ( Sus scrofa ) with intestinal damage using quantitative real-time PCR (qPCR) and hematoxylin and eosin (HE) staining. Then, we used qPCR to identify expression differences of intestinal barrier genes between the PEDV-infected and control groups. The results showed that the expression levels of most genes were significantly different between the two groups. Hierarchical clustering and correlation [...]

Reply to commentary on Serological evidence of Japanese encephalitis virus infection in pigs in a low human incidence state, Goa, India

Reply to commentary on Serological evidence of Japanese encephalitis virus infection in pigs in a low human incidence state, Goa, India

A unique feature of swine ANP32A provides susceptibility to avian influenza virus infection in pigs.

Both the replication and transcription of the influenza virus are catalyzed by the viral polymerase complex. The polymerases of most avian influenza A viruses have poor performance in mammalian cells, which is considered to be one of the important species barriers. Pigs have been long considered as important intermediate hosts for interspecies transmission of the avian influenza virus, because of their susceptibility to infection with both avian and mammalian influenza viruses. However, the molecular basis of influenza polymerase adaptation in pigs remains largely unknown. ANP32A and ANP32B proteins have been identified as playing fundamental roles in influenza virus replication and host range determination. In this study, we found that swine ANP32A (swANP32A), unlike swine ANP32B or other mammalian ANP32A or B, shows stronger supporting activity to avian viral polymerase. Knockout of ANP32A in pig cells PK15 dramatically reduced avian influenza polymerase activity and viral infectivity, suggesting a unique feature of swANP32A in supporting avian influenza viral polymerase. This species-specific activity is mapped to two key sites, 106V and 156S, in swANP32A. Interestingly, the amino acid 106V is unique to pigs among all the vertebrate species studied, and when combined with 156S, exhibits positive epistasis in pigs. Mutation of 106V and 156S to the signature found in ANP32As from other mammalian species weakened the interaction between swANP32A and chicken viral polymerase, and reduced polymerase activity. Understanding the molecular basis of ANP32 proteins may help to discover new antiviral targets and design avian influenza resistant genome edited pigs.

Pulmonary inflammatory response to influenza virus infection in pigs is regulated by DAP12 and macrophage M1 and M2 phenotypes

We delineated the expression of DAP12 (DNAX-Activating Protein) and its associated receptors, TREM-1, TREM-2 and MDL-1 in pig alveolar monocyte/macrophages (AMM) that have attained M1 or M2 phenotypes. Pig AMM stimulated in vitro with IFN-γ and IL-4 induced the expression of M1 (TNFα and iNOS) and M2 (ARG1 and no MMR) phenotypic markers, respectively. In influenza virus infected pigs at seven days post-infection, in addition to substantial modulations in the M1 and M2 markers expression, DAP12, TREM-1 and MDL-1 were downregulated in AMM. Thus, DAP12 signaling promoted the anti-inflammatory pathway in AMM of influenza virus infected pigs.

Serological evidence of Japanese encephalitis virus infection in pigs in a low human incidence state, Goa, India

Japanese encephalitis (JE) is a mosquito-borne zoonosis caused by Japanese encephalitis virus (JEV). It is a leading cause of encephalitis in humans especially children in Asia. Aquatic wading birds are the reservoirs and pigs serve as amplifying hosts for JEV. Humans and horses are dead-end hosts. JE is endemic in several states of India. Goa, a small state on the west coast of India, had witnessed JE outbreaks in the past and as on date human JE cases are reported sporadically. Although human JE cases are well documented in Goa, the status of JEV exposure of pigs has not been well documented. Hence the present study was undertaken with an objective of identifying JEV exposure in the pig population of Goa state in the light of declining human JE cases. To achieve the objective, between January 2017 and May 2019, serum samples from 666 pigs were screened using enzyme-linked immunosorbent assay (ELISA) for the detection of anti-JEV IgG. The apparent prevalence of anti-JEV IgG in pigs was found to be 7.1 % (95 % confidence interval 5.3 %–9.3 %) and true prevalence was 4.6 % (95 % confidence interval 2.7 %–7.1 %). The seroprevalence of JE recorded in pigs of Goa state was low compared to other endemic states in India, which may also be one of the reasons for the lower prevalence of human JE cases in Goa state. Univariate analysis revealed that the age of the pigs and district did not significantly influence the JE seroprevalence in pigs of Goa state. However, in multivariable logistic regression, the North Goa district was found to significantly (p = 0.017) influence the JE seroprevalence in pigs. The study identified that JEV is still circulating in the Goan pig population and hence constant vigil is required to monitor the intensity of JEV circulation in pigs. Besides forewarning possible human outbreaks in the locality, evidence of JEV exposure in pig population provides valuable data on the magnitude and extent of geographical spread.

Predicting vaccine effectiveness in livestock populations: A theoretical framework applied to PRRS virus infections in pigs.

Vaccines remain one of the main tools to control infectious diseases in domestic livestock. Although a plethora of veterinary vaccines are on the market and routinely applied to protect animals against infection with particular pathogens, the disease in question often continues to persist, sometimes at high prevalence. The limited effectiveness of certain vaccines in the field leaves open questions regarding the required properties that an effective vaccine should have, as well as the most efficient vaccination strategy for achieving the intended goal of vaccination programmes. To date a systematic approach for studying the combined effects of different types of vaccines and vaccination strategies is lacking. In this paper, we develop a theoretical framework for modelling the epidemiological consequences of vaccination with imperfect vaccines of various types, administered using different strategies to herds with different replacement rates and heterogeneity in vaccine responsiveness. Applying the model to the Porcine Reproductive and Respiratory Syndrome (PRRS), which despite routine vaccination remains one of the most significant endemic swine diseases worldwide, we then examine the influence of these diverse factors alone and in combination, on within-herd virus transmission. We derive threshold conditions for preventing infection invasion in the case of imperfect vaccines inducing limited sterilizing immunity. The model developed in this study has practical implications for the development of vaccines and vaccination programmes in livestock populations not only for PRRS, but also for other viral infections primarily transmitted by direct contact.