Stability of classical swine fever virus and pseudorabies virus in animal feed ingredients exposed to transpacific shipping conditions.

Classical swine fever virus (CSFV) and pseudorabies virus (PRV) are two of the most significant trade-limiting pathogens affecting swine worldwide. Both viruses are endemic to China where millions of kilograms of feed ingredients are manufactured and subsequently imported into the United States. Although stability and oral transmission of both viruses through contaminated pork products has been demonstrated as a risk factor for transboundary spread, stability in animal feed ingredients had yet to be investigated. The objective of this study was to determine the survival of CSFV and variant PRV in 12 animal feeds and ingredients exposed to environmental conditions simulating a 37-day transpacific shipment. Virus was detected by PCR, virus isolation and nursery pig bioassay. CSFV and PRV nucleic acids were stable throughout the 37-day period in all feed matrices. Infectious CSFV was detected in two ingredients (conventional soybean meal and pork sausage casings) at 37 days post-contamination, whereas infectious PRV was detected in nine ingredients (conventional and organic soybean meal, lysine, choline, vitamin D, moist cat and dog food, dry dog food and pork sausage casings). This study demonstrates the relative stability of CSFV and PRV in different feed ingredients under shipment conditions and provides evidence that feed ingredients may represent important risk factors for the transboundary spread of these viruses.

Effect of bovine leukemia virus on bovine mammary epithelial cells.

Bovine leukemia virus (BLV) is a retrovirus that infects cattle and is associated with an increase in secondary infections. The objective of this study was to analyze the effect of BLV infection on cell viability, apoptosis and morphology of a bovine mammary epithelial cell line (MAC-T), as well as Toll like receptors (TLR) and cytokine mRNA expression. Our findings show that BLV infection causes late syncytium formation, a decrease in cell viability, downregulation of the anti-apoptotic gene Bcl-2, and an increase in TLR9 mRNA expression. Moreover, we analyzed how this stably infected cell line respond to the exposure to Staphylococcus aureus (S. aureus), a pathogen known to cause chronic mastitis. In the presence of S. aureus, MAC-T BLV cells had decreased viability and decreased Bcl-2 and TLR2 mRNA expression. The results suggest that mammary epithelial cells infected with BLV have altered the apoptotic and immune pathways, probably affecting their response to bacteria and favoring the development of mastitis.

Correction: Survival of viral pathogens in animal feed ingredients under transboundary shipping models.

[This corrects the article DOI: 10.1371/journal.pone.0194509.].

Fecal Microbiota Transplantation Is Associated With Reduced Morbidity and Mortality in Porcine Circovirus Associated Disease.

Porcine circovirus associated disease (PCVAD) is a term used to describe the multi-factorial disease syndromes caused by porcine circovirus type 2 (PCV-2), which can be reproduced in an experimental setting through the co-infection of pigs with PCV-2 and porcine reproductive and respiratory syndrome virus (PRRSV). The resulting PCVAD-affected pigs represent a subpopulation within the co-infected group. In co-infection studies, the presence of increased microbiome diversity is linked to a reduction in clinical signs. In this study, fecal microbiota transplantation (FMT) was investigated as a means to prevent PCVAD in pigs co-infected with PRRSV and PCV-2d. The sources of the FMT material were high-parity sows with a documented history of high health status and robust litter characteristics. The analysis of the donated FMT material showed the absence of common pathogens along with the presence of diverse microbial phyla and families. One group of pigs (n = 10) was administered the FMT while a control group (n = 10) was administered a sterile mock-transplant. Over the 42-day post-infection period, the FMT group showed fewer PCVAD-affected pigs, as evidenced by a significant reduction in morbidity and mortality in transplanted pigs, along with increased antibody levels. Overall, this study provides evidence that FMT decreases the severity of clinical signs following co-infection with PRRSV and PCV-2 by reducing the prevalence of PCVAD.

Survival of viral pathogens in animal feed ingredients under transboundary shipping models.

The goal of this study was to evaluate survival of important viral pathogens of livestock in animal feed ingredients imported daily into the United States under simulated transboundary conditions. Eleven viruses were selected based on global significance and impact to the livestock industry, including Foot and Mouth Disease Virus (FMDV), Classical Swine Fever Virus (CSFV), African Swine Fever Virus (ASFV), Influenza A Virus of Swine (IAV-S), Pseudorabies virus (PRV), Nipah Virus (NiV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), Swine Vesicular Disease Virus (SVDV), Vesicular Stomatitis Virus (VSV), Porcine Circovirus Type 2 (PCV2) and Vesicular Exanthema of Swine Virus (VESV). Surrogate viruses with similar genetic and physical properties were used for 6 viruses. Surrogates belonged to the same virus families as target pathogens, and included Senecavirus A (SVA) for FMDV, Bovine Viral Diarrhea Virus (BVDV) for CSFV, Bovine Herpesvirus Type 1 (BHV-1) for PRV, Canine Distemper Virus (CDV) for NiV, Porcine Sapelovirus (PSV) for SVDV and Feline Calicivirus (FCV) for VESV. For the remaining target viruses, actual pathogens were used. Virus survival was evaluated using Trans-Pacific or Trans-Atlantic transboundary models involving representative feed ingredients, transport times and environmental conditions, with samples tested by PCR, VI and/or swine bioassay. SVA (representing FMDV), FCV (representing VESV), BHV-1 (representing PRV), PRRSV, PSV (representing SVDV), ASFV and PCV2 maintained infectivity during transport, while BVDV (representing CSFV), VSV, CDV (representing NiV) and IAV-S did not. Notably, more viruses survived in conventional soybean meal, lysine hydrochloride, choline chloride, vitamin D and pork sausage casings. These results support published data on transboundary risk of PEDV in feed, demonstrate survival of certain viruses in specific feed ingredients ("high-risk combinations") under conditions simulating transport between continents and provide further evidence that contaminated feed ingredients may represent a risk for transport of pathogens at domestic and global levels.

Correction: Survival of viral pathogens in animal feed ingredients under transboundary shipping models.

[This corrects the article DOI: 10.1371/journal.pone.0194509.].