Comparison of Thermal and Non-Thermal Processing of Swine Feed and the Use of Selected Feed Additives on Inactivation of Porcine Epidemic Diarrhea Virus (PEDV)

Evaluation of Extended Storage of Swine Complete Feed for Inactivation of Viral Contamination and Effect on Nutritional, Microbiological, and Toxicological Profiles

The extended storage of feed ingredients has been suggested as a method to mitigate the risk of pathogen transmission through contaminated ingredients. To validate the approach of extended storage of complete swine feed for the inactivation of swine viruses, an experiment was conducted wherein swine feed was inoculated with 10 mL of 1 × 105 TCID50/mL of porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and Senecavirus A (SVA) and stored for 58 d at 23.9 °C. Measures of feed quality were also evaluated at the initiation and conclusion of the storage period including screening for mycotoxins, characterization of select microbiological measures, and stability of phytase and dietary vitamins. Storing feed for 58 d under either ambient or anaerobic and temperature-controlled storage conditions did not result in substantial concerns related to microbiological profiles. Upon exposure to the feed following 58 d of storage in a swine bioassay, previously confirmed naïve pigs showed no signs of PEDV or SVA replication as detected by the PCR screening of oral fluids and serum antibody screening. Infection with SVA was documented in the positive control room through diagnostic testing through the State of Minnesota. For PRRSV, the positive control room demonstrated infection. For rooms consuming inoculated feed stored for 58 d, there was no evidence of PRRSV infection with the exception of unintentional aerosol transmission via a documented biocontainment breach. In summary, storing feed for 58 d at anaerobic and temperature-controlled environmental conditions of 23.9 °C validates that the extended storage of complete swine feed can be a method to reduce risks associated with pathogen transmission through feed while having minimal effects on measures of nutritional quality.

Biosecurity and Mitigation Strategies to Control Swine Viruses in Feed Ingredients and Complete Feeds

No system nor standardized analytical procedures at commercial laboratories exist to facilitate and accurately measure potential viable virus contamination in feed ingredients and complete feeds globally. As a result, there is high uncertainty of the extent of swine virus contamination in global feed supply chains. Many knowledge gaps need to be addressed to improve our ability to prevent virus contamination and transmission in swine feed. This review summarizes the current state of knowledge involving: (1) the need for biosecurity protocols to identify production, processing, storage, and transportation conditions that may cause virus contamination of feed ingredients and complete feed; (2) challenges of measuring virus inactivation; (3) virus survival in feed ingredients during transportation and storage; (4) minimum infectious doses; (5) differences between using a food safety objective versus a performance objective as potential approaches for risk assessment in swine feed; (6) swine virus inactivation from thermal and irradiation processes, and chemical mitigants in feed ingredients and complete feed; (7) efficacy of virus decontamination strategies in feed mills; (8) benefits of functional ingredients, nutrients, and commercial feed additives in pig diets during a viral health challenge; and (9) considerations for improved risk assessment models of virus contamination in feed supply chains.

An assessment of enhanced biosecurity interventions and their impact on porcine reproductive and respiratory syndrome virus outbreaks within a managed group of farrow-to-wean farms, 2020-2021

Introduction

Porcine reproductive and respiratory syndrome virus (PRRSV) has been a challenge for the U.S. swine industry for over 30 years, costing producers more than $600 million annually through reproductive disease in sows and respiratory disease in growing pigs. In this study, the impact of enhanced biosecurity practices of site location, air filtration, and feed mitigation was assessed on farrow-to-wean sites managed by a large swine production management company in the Midwest United States. Those three factors varied in the system that otherwise had implemented a stringent biosecurity protocol on farrow-to-wean sites. The routine biosecurity followed commonplace activities for farrow-to-wean sites that included but were not limited to visitor registration, transport disinfection, shower-in/shower-out procedures, and decontamination and disinfection of delivered items and were audited.

Methods

Logistic regression was used to evaluate PRRSV infection by site based on the state where the site is located and air filtration use while controlling for other variables such as vaccine status, herd size, and pen vs. stall. A descriptive analysis was used to evaluate the impact of feed mitigation stratified by air filtration use.

Results

Sites that used feed mitigates as additives in the diets, air filtration of barns, and that were in less swine-dense areas appeared to experience fewer outbreaks associated with PRRSV infection. Specifically, 23.1% of farms that utilized a feed mitigation program experienced PRRSV outbreaks, in contrast to 100% of those that did not. Sites that did not use air filtration had 20 times greater odds of having a PRRSV outbreak. The strongest protective effect was found when both air filtration and feed mitigation were used. Locations outside of Minnesota and Iowa had 98.5-99% lesser odds of infection as well.

Discussion

Enhanced biosecurity practices may yield significant protective effects and should be considered for producers in swine-dense areas or when the site contains valuable genetics or many pigs.

Electron beam technology for Re-processing of personal protective equipment

Beginning with the outbreak of COVID-19 at the dawn of 2020, the continuing spread of the pandemic has challenged the healthcare market and the supply chain of Personal Protective Equipment (PPE) around the world. Moreover, the emergence of the variants of COVID-19 occurring in waves threatens the sufficient supply of PPE. Among the various types of PPE, N95 Respirators, surgical masks, and medical gowns are the most consumed and thus have a high potential for a serious shortage during such emergencies. Considering the unanticipated demand for PPE during a pandemic, re-processing of used PPE is one approach to continue to protect the health of first responders and healthcare personnel. This paper evaluates the viability and efficacy of using FDA-approved electron beam (eBeam) sterilization technology (ISO 11137) to re-process used PPE. PPEs including 3M N95 Respirators, Proxima Sirus gowns, and face shields were eBeam irradiated in different media (air, argon) over a dose range of 0-200 kGy. Several tests were then performed to examine surface properties, mechanical properties, functionality performance, discoloration phenomenon, and liquid barrier performance. The results show a reduction of filtration efficiency to about 63.6% in the N95 Respirator; however, charge regeneration may improve the re-processed efficiency. Additionally, mechanical degradation was observed in Proxima Sirus gown with increasing dose up to 100 kGy. However, no mechanical degradation was observed in the face shields after 10 times donning and doffing. Apart from the face shield, N95 Respirators and Proxima Sirus gown both show significant mechanical degradation with ebeam dose over sterilization doses (>25 kGy), indicating that eBeam technology is not appropriate for the re-processing these PPEs.

Survival of a surrogate African swine fever virus-like algal virus in feed matrices using a 23-day commercial United States truck transport model

African swine fever virus (ASFV) is a member of the nucleocytoplasmic large DNA viruses (NCLDVs) and is stable in a variety of environments, including animal feed ingredients as shown in previous laboratory experiments and simulations. Emiliania huxleyi virus (EhV) is another member of the NCLDVs, which has a restricted host range limited to a species of marine algae called Emiliania huxleyi. This algal NCLDV has many similar morphological and physical characteristics to ASFV thereby making it a safe surrogate, with results that are applicable to ASFV and suitable for use in real-world experiments. Here we inoculated conventional soybean meal (SBMC), organic soybean meal (SBMO), and swine complete feed (CF) matrices with EhV strain 86 (EhV-86) at a concentration of 6.6 × 107 virus g-1, and then transported these samples in the trailer of a commercial transport vehicle for 23 days across 10,183 km covering 29 states in various regions of the United States. Upon return, samples were evaluated for virus presence and viability using a previously validated viability qPCR (V-qPCR) method. Results showed that EhV-86 was detected in all matrices and no degradation in EhV-86 viability was observed after the 23-day transportation event. Additionally, sampling sensitivity (we recorded unexpected increases, as high as 49% in one matrix, when virus was recovered at the end of the sampling period) rather than virus degradation best explains the variation of virus quantity observed after the 23-day transport simulation. These results demonstrate for the first time that ASFV-like NCLDVs can retain viability in swine feed matrices during long-term transport across the continental United States.

Tannic acid-chelated zinc supplementation alleviates intestinal injury in piglets challenged by porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) has become a challenging problem in pig industry all over the world, causing significant profit losses. Tannins and organic zinc have been shown to exert protective effects on the intestinal dysfunction caused by endotoxins. However, there is little information on tannic acid-chelated zinc (TAZ) supplementation in the diet of newborn piglets. This study was conducted to determine the effects of TAZ on the intestinal function of piglets infected with PEDV. Thirty-two 7-day-old piglets were randomly allocated to 1 of 4 treatments in a 2 × 2 factorial design consisting of 2 diets (0 or 50 mg/kg BW TAZ) and challenge (saline or PEDV). On day 9 of the trial, 8 pigs per treatment received either sterile saline or PEDV solution at 10⁶ TCID₅₀ (50% tissue culture infectious dose) per pig. Pigs infected with PEDV had greater diarrhea rate and lower average daily gain (ADG) (P < 0.05). PEDV infection decreased plasma D-xylose concentration, most antioxidative enzyme activities in plasma and intestine, as well as the small intestinal villus height (P < 0.05). Plasma diamine oxidase and blood parameters were also affected by PEDV infection. Dietary supplementation with TAZ could ameliorate the PEDV-induced changes in all measured variables (P < 0.05). Moreover, TAZ decreased the concentration of malondialdehyde in plasma, duodenum, jejunum, and colon (P < 0.05). Collectively, our results indicated that dietary TAZ could alleviate PEDV induced damage on intestinal mucosa and antioxidative capacity, and improve the absorptive function and growth in piglets. Therefore, our novel findings also suggest that TAZ, as a new feed additive for neonatal and weaning piglets, has the potential to be an alternative to ZnO.

Inactivation of porcine epidemic diarrhea virus with electron beam irradiation under cold chain conditions

The many instances of COVID-19 outbreaks suggest that cold chains are a possible route for the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, owing to the low temperatures of cold chains, which are normally below 0 °C, there are limited options for virus inactivation. Here, high-energy electron beam (E-beam) irradiation was used to inactivate porcine epidemic diarrhea virus (PEDV) under simulated cold chain conditions. This coronavirus was used as a surrogate for SARS-CoV-2. The possible mechanism by which high-energy E-beam irradiation inactivates PEDV was also explored. An irradiation dose of 10 kGy reduced the PEDV infectious viral titer by 1.68-1.76 log₁₀TCID 50 / 100 μ L in the cold chain environment, suggesting that greater than 98.1% of PEDV was inactivated. E-beam irradiation at 5-30 kGy damaged the viral genomic RNA with an efficiency of 46.25%-92.11%. The integrity of the viral capsid was disrupted at 20 kGy. The rapid and effective inactivation of PEDV at temperatures below freezing indicates high-energy E-beam irradiation as a promising technology for disinfecting SARS-CoV-2 in cold chain logistics to limit the transmission of COVID-19.

Invited review: strategic adoption of antibiotic-free pork production: the importance of a holistic approach

The discovery of the use of antibiotics to enhance growth in the 1950s proved to be one of the most dramatic and influential in the history of animal agriculture. Antibiotics have served animal agriculture, as well as human and animal medicine, well for more than seven decades, but emerging from this tremendous success has been the phenomenon of antimicrobial resistance. Consequently, human medicine and animal agriculture are being called upon, through legislation and/or marketplace demands, to reduce or eliminate antibiotics as growth promotants and even as therapeutics. As explained in this review, adoption of antibiotic-free (ABF) pork production would represent a sea change. By identifying key areas requiring attention, the clear message of this review is that success with ABF production, also referred to as "no antibiotics ever," demands a multifaceted and multidisciplinary approach. Too frequently, the topic has been approached in a piecemeal fashion by considering only one aspect of production, such as the use of certain feed additives or the adjustment in health management. Based on the literature and on practical experience, a more holistic approach is essential. It will require the modification of diet formulations to not only provide essential nutrients and energy, but to also maximize the effectiveness of normal immunological and physiological capabilities that support good health. It must also include the selection of effective non-antibiotic feed additives along with functional ingredients that have been shown to improve the utility and architecture of the gastrointestinal tract, to improve the microbiome, and to support the immune system. This holistic approach will require refining animal management strategies, including selection for more robust genetics, greater focus on care during the particularly sensitive perinatal and post-weaning periods, and practices that minimize social and environmental stressors. A clear strategy is needed to reduce pathogen load in the barn, such as greater emphasis on hygiene and biosecurity, adoption of a strategic vaccine program and the universal adoption of all-in-all-out housing. Of course, overall health management of the herd, as well as the details of animal flows, cannot be ignored. These management areas will support the basic biology of the pig in avoiding or, where necessary, overcoming pathogen challenges without the need for antibiotics, or at least with reduced usage.

Characterization of in vitro stability for two processive endoglucanases as exogenous fibre biocatalysts in pig nutrition

Development of highly efficacious exogenous fibre degradation enzymes can enhance efficiency of dietary fibre utilization and sustainability of global pork production. The objectives of this study were to investigate in vitro stability for two processive endoglucanases, referred to as GH5-tCel5A1 and GH5-p4818Cel5_2A that were overexpressed in CLEARCOLIBL21(DE3). Three-dimensional models predicted presence of Cys residues on the catalytic site surfaces of GH5-tCel5A1 and GH5-p4818Cel5_2A; and time course experimental results shown that both cellulases were susceptible to auto-oxidation by airborne O2 and were unstable. Furthermore, we examined these endoglucanases' stability under the mimicked in vitro porcine gastric and the small intestinal pH and proteases' conditions. Eadie-Hofstee inhibition kinetic analyses showed that GH5-tCel5A1 and GH5-p4818Cel5_2A respectively lost 18 and 68% of their initial activities after 2-h incubations under the gastric conditions and then lost more than 90% of their initial activities after 2-3 h of incubations under the small intestinal conditions. Therefore, further enzyme protein engineering to improve resistance and alternatively post-fermentation enzyme processing such as coating to bypass the gastric-small intestinal environment will be required to enable these two processive endoglucanases as efficacious exogenous fibre enzymes in pig nutrition application.

Monoglyceride reduces viability of porcine epidemic diarrhoea virus in feed and prevents disease transmission to post-weaned piglets

Outbreaks of African swine fever virus (ASFv) and porcine epidemic diarrhoea virus (PEDv) have revealed the susceptibility of livestock to disease transmitted through feed. Several viruses, including PEDv, survive in feed and may introduce disease that causes significant morbidity and mortality. In 2013, PEDv, which causes severe diarrhoea and vomiting, reached North America after spreading for decades across Eurasia. The global exchange of ingredients has created demand for products that prevent disease transmission from feed. Formaldehyde-based products are highly effective at inactivating enveloped viruses when applied at 3.25 kg/t. Alternative products to formaldehyde, including carboxylic acids, essential oils and medium chain fatty acids (MCFAs), have exhibited mixed efficacy against PEDv and require application rates higher than formaldehyde. Amphiphilic molecules like MCFAs disrupt the bilayer-lipid membranes that protect viral nucleic acids through the formation of micelles. Monoglycerides form micelles at lower concentrations than MCFAs, which suggests they may be more potent against enveloped viruses. The potential efficacy of monoglycerides against enveloped viruses in feed led to the development and examination of an experimental monoglyceride blend. The proprietary monoglyceride blend significantly (p < .0001) reduced PEDv viability in vitro after application to feed at 1.5, 2.5 and 3.5 kg/t. The monoglyceride was tested in a natural feeding behaviour challenge model in piglets. The feed was contaminated with ice-blocks containing viable PEDv, and the piglets were exposed to PEDv through the feed bin for 20 days. At the end of the 20-day challenge period, all pigs were rectally swabbed and tested for PEDv by qPCR. In the untreated control group 54.8% of the piglets tested positive for PEDv, whereas none of the MCFA-treated feed (10 kg/t inclusion) transmitted PEDv. Strikingly, the monoglyceride-treated groups (1.5, 2.5 and 3.5 kg/t) all exhibited 100% protection from PEDv. These data support the use of this proprietary monoglyceride blend in mitigation and prevention of viral disease transmission to piglets from contaminated feed.

Radiation Inactivation of Coronavirus Infection Pathogen by the Example of Transmissible Gastroenteritis Virus

In recent years, members of the Coronaviridae family have caused outbreaks of respiratory diseases (MERS, SARS, and COVID-19). At the same time, the potential of radiation-induced inactivation of this group of viruses have been little studied, although radiation technologies can be widely used both in the processing of personal protective equipment and in the sterilization of vaccines. In the present work, the effect of 10 MeV electron beams and 7.6 MeV bremsstrahlung on the coronavirus infection pathogen (transmissible gastroenteritis virus) has been studied in vitro. In the given experimental conditions, irradiation with photons turned out to be more effective. The virus-containing suspension frozen at -86°C was the most resistant to radiation: the dose required for complete inactivation of the virus in this case was from 15 kGy, while for the liquid suspension and lyophilized form the sterilizing dose was from 10 kGy. At lower radiation doses for all samples during passaging in cell culture, residual infectious activity of the virus was observed. These differences in the efficiency of inactivation of liquid and frozen virus-containing samples indicate a significant contribution of the direct effect of radiation.

Porcine deltacoronavirus and its prevalence in China: a review of epidemiology, evolution, and vaccine development

Porcine deltacoronavirus (PDCoV) is one of the most important enteropathogenic pathogens, and it causes enormous economic losses to the global commercial pork industry. PDCoV was initially reported in Hong Kong (China) in 2012 and subsequently emerged in swine herds with diarrhea in Ohio (USA) in 2014. Since then, it has spread to Canada, South Korea, mainland China, and several Southeast Asian countries. Information about the epidemiology, evolution, prevention, and control of PDCoV and its prevalence in China has not been comprehensively reported, especially in the last five years. This review is an update of current information on the general characteristics, epidemiology, geographical distribution, and evolutionary relationships, and the status of PDCoV vaccine development, focusing on the prevalence of PDCoV in China and vaccine research in particular. Together, this information will provide us with a greater understanding of PDCoV infection and will be helpful for establishing new strategies for controlling this virus worldwide.

Can we effectively manage parasites, prions, and pathogens in the global feed industry to achieve One Health?

Prions and certain endoparasites, bacteria, and viruses are internationally recognized as types of disease-causing biological agents that can be transmitted from contaminated feed to animals. Historically, foodborne biological hazards such as prions (transmissible spongiform encephalopathy), endoparasites (Trichinella spiralis, Toxoplasma gondii), and pathogenic bacteria (Salmonella spp., Listeria monocytogenes, Escherichia coli O157, Clostridium spp., and Campylobacter spp.) were major food safety concerns from feeding uncooked or improperly heated animal-derived food waste and by-products. However, implementation of validated thermal processing conditions along with verifiable quality control procedures has been effective in enabling safe use of these feed materials in animal diets. More recently, the occurrence of global Porcine Epidemic Diarrhea Virus and African Swine Fever Virus epidemics, dependence on international feed ingredient supply chains, and the discovery that these viruses can survive in some feed ingredient matrices under environmental conditions of trans-oceanic shipments has created an urgent need to develop and implement rigorous biosecurity protocols that prevent and control animal viruses in feed ingredients. Implementation of verifiable risk-based preventive controls, traceability systems from origin to destination, and effective mitigation procedures is essential to minimize these food security, safety, and sustainability threats. Creating a new biosafety and biosecurity framework will enable convergence of the diverging One Health components involving low environmental impact and functional feed ingredients that are perceived as having elevated biosafety risks when used in animal feeds.

New perspectives for evaluating relative risks of African swine fever virus contamination in global feed ingredient supply chains

There are no published reports indicating that the African swine fever virus (ASFV) has been detected in feed ingredients or complete feed. This is primarily because there are only a few laboratories in the world that have the biosecurity and analytical capabilities of detecting ASFV in feed. Several in vitro studies have been conducted to evaluate ASFV concentration, viability and inactivation when ASFV was added to various feed ingredients and complete feed. These inoculation studies have shown that some feed matrices support virus survival longer than others and the reasons for this are unknown. Current analytical methodologies have significant limitations in sensitivity, repeatability, ability to detect viable virus particles and association with infectivity. As a result, interpretation of findings using various measures may lead to misleading conclusions. Because of analytical and technical challenges, as well as the lack of ASFV contamination data in feed supply chains, quantitative risk assessments have not been conducted. A few qualitative risk assessments have been conducted, but they have not considered differences in potential scenarios for ASFV contamination between various types of feed ingredient supply chains. Therefore, the purpose of this review is to provide a more holistic understanding of the relative potential risks of ASFV contamination in various global feed ingredient supply chains and provide recommendations for addressing the challenges identified.

Risk and Mitigation of African Swine Fever Virus in Feed

Simple Summary

African 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.

Abstract

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.

Effects of medium chain fatty acids as a mitigation or prevention strategy against porcine epidemic diarrhea virus in swine feed

Feed has been shown to be a vector for viral transmission. Four experiments were conducted to: 1) determine if medium chain fatty acids (MCFA) are effective mitigants when applied to feed both pre- and post-porcine epidemic diarrhea virus (PEDV) inoculation measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR), 2) evaluate varying levels and combinations of MCFA measured by qRT-PCR, and 3) evaluate selected treatments in bioassay to determine infectivity. In exp. 1, treatments were arranged in a 2 × 2 + 1 factorial with main effects of treatment (0.3% commercial formaldehyde [CF] product, Sal CURB [Kemin Industries, Inc.; Des Moines, IA], or 1% MCFA blend (Blend) of 1:1:1 C6:C8:C10 [PMI, Arden Hills, MN]) and timing of application (pre- or post-inoculation with PEDV) plus a positive control (PC; feed inoculated with PEDV and no treatment). All combinations of treatment and timing decreased detectable PEDV compared with the PC (P < 0.05). Pre-inoculation treatment elicited decreased magnitude of PEDV detection (cycle threshold value) compared with post-inoculation (P = 0.009). Magnitude of PEDV detection was decreased for CF compared with Blend (P < 0.0001). In exp. 2, pre-inoculation treatments consisted of: 1) PC, 2) 0.3% CF, 3 to 5) 0.125% to 0.33% C6:0, 6 to 8) 0.125% to 0.33% C8:0, 9 to 11) 0.125% to 0.33% C10:0, and 12 to 15) 0.125% to 0.66% C5:0. Treating feed with 0.33% C8:0 resulted in decreased (P < 0.05) PEDV detection compared with all other treatments. Increasing concentration of each individual MCFA decreased PEDV detectability (P < 0.042). In exp. 3, pre-inoculation treatments consisted of: 1) PC, 2) 0.3% CF, 3 to 7) 0.25% to 1% Blend, 8 to 10) 0.125% to 0.33% C6:0 + C8:0, 11 to 13) 0.125% to 0.33% C6:0 + C10:0, and 14 to 16) 0.125% to 0.33% C8:0 + C10:0. Treating feed with CF, 0.5% Blend, 0.75% Blend, 1% Blend, all levels of C6:0+C8:0, 0.25% C6:0 + 0.25% C10:0, 0.33% C6:0 + 0.33% C10:0, 0.25% C8:0 + 0.25% C10:0, or 0.33% C8:0 + 0.33% C10:0 elicited decreased detection of PEDV compared with PC (P < 0.05). Increasing concentration of each MCFA combination decreased PEDV detectability (linear, P < 0.012). In exp. 4, feed was treated pre-inoculation with: 1) no treatment (PC), 2) 0.3% CF, 3) 0.5% Blend, or 4) 0.3% C8:0 and analyzed via qRT-PCR and bioassay. Adding 0.5% Blend or 0.3% C8:0 resulted in decreased PEDV compared with PC and only PC resulted in a positive bioassay. Therefore, MCFA can decrease detection of PEDV in feed. Further, inclusion of lower levels of MCFA than previously evaluated are effective against PEDV.

Rapid Selective Detection of Potentially Infectious Porcine Epidemic Diarrhea Coronavirus Exposed to Heat Treatments Using Viability RT-qPCR

Coronaviruses (CoVs) cause severe respiratory, enteric, and systemic infections in a wide range of hosts, including humans and animals. Porcine epidemic diarrhea virus (PEDV), a member of the Coronaviridae family, is the etiological agent of porcine epidemic diarrhea (PED), a highly contagious intestinal disease affecting pigs of all ages. In this study, we optimized a viability real-time reverse transcriptase polymerase chain reaction (RT-qPCR) for the selective detection of infectious and heat-inactivated PEDV. PEMAX™, EMA™, and PMAxx™ photoactivable dyes along with PtCl₄ and CDDP platinum compounds were screened as viability markers using two RT-qPCR assays: firstly, on PEDV purified RNA, and secondly on infectious and thermally inactivated virus suspensions. Furthermore, PMAxx™ pretreatment matched the thermal inactivation pattern obtained by cell culture better than other viability markers. Finally, we further optimized the pretreatment by coupling viability markers with Triton X-100 in inoculated serum resulting in a better estimation of PEDV infectivity than RT-qPCR alone. Our study has provided a rapid analytical tool based on viability RT-qPCR to infer PEDV infectivity with potential application for feed and feed ingredients monitoring in swine industry. This development would allow for greater accuracy in epidemiological surveys and outbreak investigations.

An evaluation of additives for mitigating the risk of virus-contaminated feed using an ice-block challenge model

The role of animal feed as a vehicle for the transport and transmission of viral diseases was first identified during the porcine epidemic diarrhoea virus (PEDV) epidemic in North America. Since that time, various feed additives have been evaluated at the laboratory level to measure their effect on viral viability and infectivity in contaminated feed using bioassay piglet models. While a valid first step, the conditions of these studies were not representative of commercial swine production. Therefore, the purpose of this study was to evaluate the ability of feed additives to mitigate the risk of virus‐contaminated feed using a model based on real‐world conditions. This new model used an ‘ice‐block’ challenge, containing equal concentrations of porcine reproductive and respiratory syndrome virus (PRRSV), Senecavirus A (SVA) and PEDV, larger populations of pigs, representative commercial facilities and environments, along with realistic volumes of complete feed supplemented with selected additives. Following supplementation, the ice block was manually dropped into designated feed bins and pigs consumed feed by natural feeding behaviour. After challenge, samples were collected at the pen level (feed troughs, oral fluids) and at the animal level (clinical signs, viral infection, growth rate, and mortality) across five independent experiments involving 15 additives. In 14 of the additives tested, pigs on supplemented diets had significantly greater average daily gain (ADG), significantly lower clinical signs and infection levels, and numerically lower mortality rates compared to non‐supplemented controls. In conclusion, the majority of the additives evaluated mitigated the effects of PRRSV 174, PEDV and SVA in contaminated feed, resulting in improved health and performance.

Mitigating the risk of African swine fever virus in feed with anti-viral chemical additives

African swine fever (ASF) is currently considered the most significant global threat to pork production worldwide. Disease caused by the ASF virus (ASFV) results in high case fatality of pigs. Importantly, ASF is a trade-limiting disease with substantial implications on both global pork and agricultural feed commodities. ASFV is transmissible through natural consumption of contaminated swine feed and is broadly stable across a wide range of commonly imported feed ingredients and conditions. The objective of the current study was to investigate the efficacy of medium-chain fatty acid and formaldehyde-based feed additives in inactivating ASFV. Feed additives were tested in cell culture and in feed ingredients under a transoceanic shipment model. Both chemical additives reduced ASFV infectivity in a dose-dependent manner. This study provides evidence that chemical feed additives may potentially serve as mitigants for reducing the risk of ASFV introduction and transmission through feed.

The risk of viral transmission in feed: What do we know, what do we do?

The role of animal feed as a vehicle for the transport and transmission of viral diseases was first identified in 2014 during the porcine epidemic diarrhoea virus epidemic in North America. Since the identification of this novel risk factor, scientists have conducted numerous studies to understand its relevance. Over the past few years, the body of scientific evidence supporting the reality of this risk has grown substantially. In addition, numerous papers describing actions and interventions designed to mitigate this risk have been published. Therefore, the purpose of this paper is to review the literature on the risk of feed (what do we know) and the protocols developed to reduce this risk (what do we do) in an effort to develop a comprehensive document to raise awareness, facilitate learning, improve the accuracy of risk assessments and to identify knowledge gaps for future studies.

Prevalence of Porcine Pseudorabies Virus and Its Coinfection Rate in Heilongjiang Province in China from 2013 to 2018

Pseudorabies (PR) is a highly contagious disease affecting a wide range of animals, which annually causes great economic losses in China. In this study, a total number of 18,815 serum samples and 1,589 tissue samples were collected from 311 intensive pig farms (≥350 sows) located in eight cities in Heilongjiang province, and tested by ELISA and PCR. Overall, the serum positive rates of gE and gB protein were 16.3% and 84.5%, respectively. The PCR-positive rate of PR virus (PRV) in tissue samples was 17.8%. The coinfection rates of PRV with porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), and classical swine fever virus (CSFV) were also measured. The rate of PRV coinfected with PRRSV was 36.0% followed by 12.9% with PCV2 and 1.8% with CSFV, respectively. These results clearly demonstrate PRV prevalence and its coinfection rate in Heilongjiang province, indicating high PR endemic in pig farms in this region. This study provides data for further epidemiological investigations and a reference for developing PRV control strategies in this region and in China.

Assessing the effects of medium-chain fatty acids and fat sources on PEDV infectivity

The overall objective of this study was to compare the efficacy of medium-chain fatty acids (MCFA) to other common fat sources to minimize the risk of porcine epidemic diarrhea virus (PEDV) cross-contamination in a pig bioassay. Treatments were feed with mitigants inoculated with PEDV after application and were: 1) positive control with no chemical treatment; 2) 0.325% commercially available formaldehyde-based product; 3) 1% blend of 1:1:1 caproic (C6), caprylic (C8), and capric acids (C10) and applied with an aerosolizing nozzle; 4) treatment 3 applied directly into the mixer without an aerosolizing nozzle; 5) 0.66% caproic acid; 6) 0.66% caprylic acid; 7) 0.66% capric acid; 8) 0.66% lauric acid; 9) 1% blend of 1:1 capric and lauric acids; 10) 0.3% commercially available dry C12 product; 11) 1% canola oil; 12) 1% choice white grease; 13) 2% coconut oil; 14) 1% coconut oil; 15) 2% palm kernel oil; 16) 1% palm kernel oil; 17) 1% soy oil and four analysis days (0, 1, 3, and 7 post inoculation) as well as 1 treatment of PEDV-negative feed without chemical treatment. There was a treatment × day interaction (P < 0.002) for detectable PEDV RNA. The magnitude of the increase in Ct value from d 0 to 7 was dependent upon the individual treatments. Feed treated with individual MCFA, 1% MCFA blend, or commercial-based formaldehyde had fewer (P < 0.05) detectable viral particles than all other treatments. Commercial-based formaldehyde, 1% MCFA, 0.66% caproic, 0.66% caprylic, and 0.66% capric acids had no evidence of infectivity 10-d old pig bioassay, while there was no evidence the C12 commercial product or longer chain fat sources inhibited PEDV infectivity. Interestingly, pigs given the coconut oil source with the highest composition of caprylic and capric only showed signs of infectivity on the last day of bioassay. These data suggest some MCFA have potential for reducing post feed manufacture PEDV contamination.

Determining the impact of commercial feed additives as potential porcine epidemic diarrhea virus mitigation strategies as determined by polymerase chain reaction analysis and bioassay

Mitigation of porcine epidemic diarrhea virus (PEDV) was assessed using two feed additives (0.5% inclusion of a benzoic acid [BA] product and 0.02% inclusion of an essential oil [EO] product; DSM Nutritional Products Inc., Parsippany, NJ), and combination of both products (0.5% BA and 0.02% EO) in spray-dried porcine plasma (SDPP) and a swine gestation diet (FEED) as determined by real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and bioassay. Viral RNA quantification was performed at 7 sampling days post-laboratory inoculation (d 0, 1, 3, 7, 14, 21, and 42) and infectivity was assessed via bioassay with 10-d-old pigs. There was a tendency for treatment × feed matrix × day interaction (P = 0.094), in which the cycle threshold (Ct) value increased over time in FEED when treated with both feed additives, whereas there was no increase over time observed in SDPP treated with both feed additives. There was a feed matrix × day interaction (P < 0.001) in which Ct increased over time in FEED, whereas very little increase over time was observed in SDPP. A tendency for a treatment × feed matrix effect (P = 0.085) was observed where FEED treated with the combination of EO and BA had a greater (P < 0.05) PEDV Ct value than other FEED treatments, and all SDPP treatments had the lower PEDV Ct values compared to FEED treatments (P < 0.05). Overall, the combination of both feed additives was most effective at reducing the quantity of genetic material as detected by qRT-PCR (P < 0.001) compared to either additive alone or no feed additive. Virus shedding was observed in the d 7 postinoculation SDPP treatment that was treated with both feed additives, as well as d 0 untreated FEED and d 0 FEED treated with both feed additives. No other treatment bioassay room had detectible RNA shed and detected in fecal swabs or cecal contents. In summary, the combination of EO and BA enhanced the degradation of PEDV RNA in feed but had little impact on RNA degradation in SDPP. Both untreated feed and feed treated with the combination of EO and BA resulted in infection at d 0 post-laboratory inoculation; however, neither set of samples was infective at d 1 postinoculation. In addition, SDPP harbored greater levels of quantifiable RNA for a longer duration of time compared to FEED, and these viral particles remained viable for a longer duration of time indicating differences in viral stability exist between different feed matrices.

Evaluation of the effects of flushing feed manufacturing equipment with chemically treated rice hulls on porcine epidemic diarrhea virus cross-contamination during feed manufacturing

Various strategies have been proposed to mitigate potential risk of porcine epidemic diarrhea virus (PEDV) transmission via feed and feed ingredients. Wet disinfection has been found to be the most effective decontamination of feed mill surfaces; however, this is not practical on a commercial feed production scale. Another potential mitigation strategy would be using chemically treated rice hulls flushed through the feed manufacturing equipment. Therefore, the objective of this study was to determine the effects of medium-chain fatty acids (MCFA) or formaldehyde-treated rice hull flush batches as potential chemical mitigation strategies for PEDV during feed manufacturing. Feed without evidence of PEDV RNA contamination was inoculated with PEDV. Based on polymerase chain reaction analysis, this feed had a cycle threshold (Ct) = 30.2 and was confirmed infective in bioassay. After manufacturing the PEDV-positive feed, untreated rice hulls, formaldehyde-treated rice hulls, 2% MCFA- (a 1:1:1 blend of hexanoic, octanoic, and decanoic acid) treated rice hulls, or 10% MCFA-treated rice hulls were flushed through laboratory scale mixers. For the untreated rice hulls, 3 of 6 samples had detectable PEDV RNA, whereas 1 of 6 formaldehyde-treated rice hull flush samples and 2 of 6 of the 2% MCFA rice hull flush samples had detectable PEDV RNA. However, PEDV RNA was not detected in any of the 10% MCFA rice hull flush samples. Then, rice hulls treated with 10% MCFA were mixed and discharged through a production scale mixer and bucket elevator following PEDV-positive feed. No rice hull flush or feed samples from the mixer following chemically treated rice hull flush had detectible PEDV RNA. However, one 10% MCFA rice hull sample collected from the bucket elevator discharge spout had detectible PEDV RNA. Dust collected following mixing of PEDV contaminated feed had detectable PEDV RNA (Ct = 29.4) and was infectious. However, dust collected immediately after the 10% MCFA rice hull flush batch had a reduced quantity of PEDV RNA (Ct = 33.7) and did not cause infection. Overall, the use of rice hull flushes effectively reduced the quantity of detectible RNA present after mixing a batch of PEDV-positive feed. Chemical treatment of rice hulls with formaldehyde or 10% MCFA provided additional reduction in detectible RNA. Finally, dust collected after manufacturing PEDV-inoculated feed has the potential to serve as a vector for PEDV transmission.

Swine enteric coronavirus disease: A review of 4 years with porcine epidemic diarrhoea virus and porcine deltacoronavirus in the United States and Canada

Swine enteric coronaviruses, including porcine epidemic diarrhoea virus (PEDV) and porcine deltacoronavirus (PDCoV), have emerged and spread throughout the North American swine industry over the last four years. These diseases cause significant losses within the pork industry and within the first year after PEDV introduction, approximately 10% of the US herd died due to the disease. Similar to other enteric coronaviruses, such as transmissible gastroenteritis virus (TGEV), these emerging swine enteric coronavirus diseases (SECD) are age-dependent, with high morbidity and mortality in neonatal pigs. Since the introduction of SECD, research has focused on investigating viral pathogenesis through experimental inoculation, increasing maternal antibody for neonatal protection, understanding transmission risks through feed and transportation, and outlining the importance of biosecurity in preventing SECD introduction and spread. A survey of swine professionals conducted for this review revealed that the majority of respondents (75%) believe SECD can be eradicated and that most herds have been successful at long-term elimination of SECD after exposure (80%). However, unique properties of SECD, such as ineffective immunity through parenteral vaccination and a low oral infectious dose, play a major role in management of SECD. This review serves to describe the current knowledge of SECD and the characteristics of these viruses which provide both opportunities and challenges for long-term disease control and potential eradication from the US swine population.

Physical and Chemical Methods for the Reduction of Biological Hazards in Animal Feeds

Feed for livestock animals have been under increased scrutiny as a vector for pathogenic bacteria leading to human illnesses. Control of these pathogenic bacteria in animal feeds can be controlled via physical and chemical means. Physical methods can include thermal processing, including irradiation, pelleting, and extrusion. Chemical mitigation can be accomplished through the inclusion of various additives, including formaldehyde, organic acids, essential oils, or medium chain fatty acids. While physical and chemical interventions can help mitigate risk of pathogens contaminating finished animal feeds, the implementation of a biosecurity plan at the feed mill can help prevent pathogens from entering or spreading throughout the facility.

Survival of porcine epidemic diarrhea virus (PEDV) in thermally treated feed ingredients and on surfaces

BACKGROUND

Infection with Porcine Epidemic Diarrhea Virus (PEDV) causes vomiting, diarrhea, and dehydration in young pigs. The virus made its first appearance in the U.S. in 2013, where it caused substantial neonatal mortality and economic losses in the U.S. pork industry. Based on outbreak investigations, it is hypothesized that the virus could be transmitted through contaminated feed or contaminated feed surfaces. This potential risk created a demand for research on the inactivation kinetics of PEDV in different environments. Therefore, the objective of this study was to evaluate the survival of PEDV in 9 different feed ingredients when exposed to 60, 70, 80, and 90 °C, as well as the survival on four different surfaces (galvanized steel, stainless steel, aluminum, and plastic).

RESULTS

Overall, there were no differences (P > 0.05) in virus survival among the different feed matrices studied when thermally processed at 60 to 90 °C for 5, 10, 15, or 30 min. However, the time necessary to achieve a one log reduction in virus concentration was less (P < 0.05) when ingredients were exposed to temperatures from 70 °C (3.7 min), 80 °C (2.4 min), and 90 °C (2.3 min) compared with 60 °C (4.4 min). The maximum inactivation level (3.9 log) was achieved when heating all ingredients at 90 °C for 30 min. There were no differences in the amount of time necessary to cause a one log reduction in PEDV concentration among the different surfaces.

CONCLUSIONS

The results of this study showed that PEDV survival among the 9 feed ingredients evaluated was not different when exposed to thermal treatments for up to 30 min. However, different combinations of temperature and time resulted in achieving a 3 to 4 log reduction of PEDV in all feed ingredients evaluated. Finally, PEDV survival was similar on galvanized steel, stainless steel, aluminum and plastic.

Effect of pelleting on survival of porcine epidemic diarrhea virus-contaminated feed

Porcine epidemic diarrhea virus (PEDV) is a heat-sensitive virus that has devastated the U.S. swine industry. Because of its heat sensitivity, we hypothesized that a steam conditioner and pellet mill mimicking traditional commercial thermal processing may mitigate PEDV infectivity. Pelleting, a common feed processing method, includes the use of steam and shear forces, resulting in increased temperature of the processed feed. Two thermal processing experiments were designed to determine if different pellet mill conditioner retention times and temperatures would impact PEDV quantity and infectivity by analysis of quantitative reverse transcription PCR and bioassay. In Exp. 1, a 3 × 3 × 2 factorial design was used with 3 pelleting temperatures (68.3, 79.4, and 90.6°C), 3 conditioning times (45, 90, or 180 s), and 2 doses of viral inoculation (low, 1 × 10 tissue culture infectious dose (the concentration used to see cytopathic effect in 50% of the cells)/g, or high, 1 × 10 tissue culture infectious dose/g). Noninoculated and PEDV-inoculated unprocessed mash were used as controls. The low-dose PEDV-infected mash had 6.8 ± 1.8 cycle threshold (Ct) greater ( < 0.05) PEDV than the high-dose mash. Regardless of time or temperature, pelleting reduced ( < 0.05) the quantity of detectable viral PEDV RNA compared with the PEDV-inoculated unprocessed mash. Fecal swabs from pigs inoculated with the PEDV-positive unprocessed mash, regardless of dose, were clinically PEDV positive from 2 to 7 d (end of the trial) after inoculation. However, if either PEDV dose of inoculated feed was pelleted at any of the 9 tested conditioning time × temperature combinations, no PEDV RNA was detected in fecal swabs or cecum content. Based on Exp. 1 results, a second experiment was developed to determine the impact of lower processing temperatures on PEDV quantity and infectivity. In Exp. 2, PEDV-inoculated feed was pelleted at 1 of 5 conditioning temperatures (37.8, 46.1, 54.4, 62.8, and 71.1°C) for 30 s. The 5 increasing processing temperatures led to feed with respective mean Ct values of 32.5, 34.6, 37.0, 36.5, and 36.7, respectively. All samples had detectable PEDV RNA. However, infectivity was detected by bioassay only in pigs from the 37.8 and 46.1°C conditioning temperatures. Experiment 2 results suggest conditioning and pelleting temperatures above 54.4°C could be effective in reducing the quantity and infectivity of PEDV in swine feed. However, additional research is needed to prevent subsequent recontamination after pelleting as it is a point-in-time mitigation step.

Environmental persistence of porcine coronaviruses in feed and feed ingredients

Porcine Epidemic Diarrhea Virus (PEDV), Porcine Delta Corona Virus (PDCoV), and Transmissible Gastroenteritis Virus (TGEV) are major threats to swine health and contaminated feed plays a role in virus transmission. The objective of our study was to characterize inactivation of PEDV, PDCoV, and TGEV in various feed ingredient matrices. Samples of complete feed, spray dried porcine plasma, meat meal, meat and bone meal, blood meal, corn, soybean meal, and corn dried distillers grains with solubles were weighed (5 g/sample) into scintillation vials and inoculated with 1 mL of PEDV, PDCoV, or TGEV. Samples were incubated at room temperature for up to 56 days. Aliquots were removed at various time points followed by preparing serial 10-fold dilutions and inoculating in cell cultures to determine the amount of surviving virus. Inactivation kinetics were determined using the Weibull model, which estimates a delta value indicating the time necessary to reduce virus concentration by 1 log. Delta values of various ingredients were compared and analyzed as to their nutrient composition. Soybean meal had the greatest delta value (7.50 days) for PEDV (P < 0.06) as compared with all other ingredients. High delta values (P < 0.001) were observed in soybean meal for PDCoV (42.04 days) and TGEV (42.00 days). There was a moderate correlation between moisture content and the delta value for PDCoV (r = 0.49, P = 0.01) and TGEV (r = 0.41, P = 0.02). There was also a moderate negative correlation between TGEV survival and ether extract content (r = -0.51, P = 0.01). In conclusion, these results indicate that the first log reduction of PDCoV and TGEV takes the greatest amount of time in soybean meal. In addition to this, moisture and ether content appear to be an important determinant of virus survival in feed ingredients.

Feed additives decrease survival of delta coronavirus in nursery pig diets

BACKGROUND

Feed contaminated with feces from infected pigs is believed to be a potential route of transmission of porcine delta coronavirus (PDCoV). The objective of this study was to determine if the addition of commercial feed additives (e.i., acids, salt and sugar) to swine feed can be an effective strategy to inactive PDCoV.

RESULTS

Six commercial feed acids (UltraAcid P, Activate DA, KEMGEST, Acid Booster, Luprosil, and Amasil), salt, and sugar were evaluated. The acids were added at the recommended concentrations to 5 g aliquots of complete feed, which were also inoculated with 1 mL of PDCoV and incubated for 0, 7, 14, 21, 28, and 35 days. In another experiment, double the recommended concentrations of these additives were also added to the feed samples and incubated for 0, 1, 3, 7, and 10 days. All samples were stored at room temperature (~25 °C) followed by removal of aliquots at 0, 7, 14, 21, 28, and 35 days. Any surviving virus was eluted in a buffer solution and then titrated in swine testicular cells. Feed samples without any additive were used as controls. Both Weibull and log-linear kinetic models were used to analyze virus survival curves. The presence of a tail in the virus inactivation curves indicated deviations from the linear behavior and hence, the Weibull model was chosen for characterizing the inactivation responses due to the better fit. At recommended concentrations, delta values (days to decrease virus concentration by 1 log) ranged from 0.62-1.72 days, but there were no differences on virus survival among feed samples with or without additives at the manufacturers recommended concentrations. Doubling the concentration of the additives reduced the delta value to ≤ 0.28 days (P < 0.05) for all the additives except for Amasil (delta values of 0.86 vs. 4.95 days). Feed additives that contained phosphoric acid, citric acid, or fumaric acid were the most effective in reducing virus survival, although none of the additives completely inactivated the virus by 10- days post-inoculation.

CONCLUSIONS

Commercial feed additives (acidifiers and salt) may be utilized as a strategy to decrease risk of PDCoV in feed, specially, commercial feed acidifiers at double the recommended concentrations reduced PDCoV survival in complete feed during storage at room temperature. However, none of these additives completely inactivated the virus.