The U.S. pork industry is importing feed ingredients from countries with endemic swine diseases not presently in the United States. Results of research funded by the Swine Health Information Center (SHIC) in 2017 suggest a subset of contaminated feed ingredients could serve as vehicles for foreign animal disease, other transboundary disease introduction to the US, and possibly circulation of viruses within the US. For example, the results of this research may provide new insights and areas for helping to understand regional spread of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV). Further investigation of potential threats posed by virus-contaminated feed ingredients and how to mitigate them will be a focus for SHIC in 2018.
In completed research about the potential for feed and feed ingredients to harbor and transport viral pathogens, the SHIC Swine Disease Matrix was used to identify target viral pathogens for evaluation in the study. Researchers used surrogate viruses in some instances, which allowed study of closely related and structurally similar viruses. Results of the study (accepted for peer-reviewed publication) conducted by Pipestone Applied Research, South Dakota State University, and Kansas State University (KSU) shows the potential for PRRSV and other viruses to contaminate and survive in feed ingredients, including soybean meal and distillers dried grains and solubles (DDGS). PEDV, African swine fever virus (ASFV), Seneca Virus A (SVA, surrogate for FMDV and of interest itself), and Bovine Herpesvirus-1 (BHV-1, surrogate for PRV), have also been found to survive in feed ingredients under the shipping time and environmental conditions from Asia or Eastern Europe to the US.
Risk mitigation research is testing several commercially available feed additives that may be added to feed during milling or other processes to neutralize or reduce the load of these pathogens in feed and help mitigate the potential risk of transport. The initial phase of the project consists of screening a panel of 10 mitigants against identified higher-risk combination of viruses and feed ingredients. The panel of viruses, which were selected based on their ability to survive in feed ingredients, include SVA (FMDV surrogate), BHV-1 (surrogate for PRV), PRRSV, PEDV, and ASFV.
The mitigation trials with SVA have been completed and results obtained with several of the feed additives tested look promising. For example, SVA titers dropped 72.6 percent, 63.9 percent, 63.9 percent, and 61.05 percent in soybean meal treated with the four most efficacious mitigants. Currently, samples spiked with PRRSV, PEDV and BHV-1 (PRV surrogate) are being processed and virus infectivity assays are being done. Those assays include a combination of cell culture virus isolation and swine bioassays to ensure detection, if live virus is still present after the mitigant was added.
Additional Feed Additive Testing Underway
At the KSU high biosecurity lab, researchers are working directly with ASF, CSF, and PRV. They are determining the potential for survival in feed and feed ingredients under the transboundary model as well as assessing tools for mitigating the risk of virus transport in feed and feed ingredients.
In work completed so far, KSU has determined ASF survived in nine of 12 different feed ingredients in a 30-day trans-Atlantic model, CSF appears not to have survived in any ingredients during a 37-day trans-Pacific model with confirmation ongoing, and the PRV test is still underway. KSU is also reviewing two mitigants – medium chain fatty acids and a formaldehyde-based product – with nine additional candidates for study being considered.
Dust Testing Holds Promise
KSU researchers are investigating using dust samples to monitor for swine pathogens in products and US feed mills. There is potential for the findings to lead to development of a diagnostic laboratory panel of assays where a single submitted swab of feed mill dust could be analyzed for multiple feed-based bacteria and viruses – a low-cost tool that could be used to help address feed safety.
The KSU research proceeds with the working hypothesis that sampling dust, instead of feed or ingredients, provides a greater representation of the population of viruses and bacteria. For example, an empty feed conveyer still contains dust from previous batches that will be in contact with subsequent batches. Plus, viruses and bacteria will not be evenly distributed throughout feed or ingredients, making sample-based testing unreliable.
While swabbing surfaces and testing dust has been proven to be effective for monitoring for some bacterial pathogens, it had not been validated for detection of SVA or viruses which have been demonstrated to survive in feed. KSU research has now confirmed the efficacy of this testing method using a SVA model. Next steps for this SHIC-funded project will be to better understand if the prevalence and distribution of SVA in domestic swine feed mills could be one factor of risk of domestic and foreign animal disease transport through feed.
In addition to the benefits of swabbing to test in domestic feed mills, this research also holds the potential of monitoring environmental surfaces from cargo holds or totes of imported ingredients to better understand the status of those ingredients. Theoretically, the process could be implemented for monitoring at ports to prevent disease entry by swabbing dust as well as actively monitoring feed mills that use imported ingredients.
Coordinated Plan for Related Research Being Developed
A group of feed expert animal scientists gathered on March 13 to outline further feed related research that needs to be done. While KSU has some preliminary results for a model testing mill dust samples for pathogens, the industry needs to have a validated way to sample bulk materials in mills and elsewhere and then know how to effectively disinfect/clean up a mill if something is found in the dust or product. Additionally, a system for process control that starts and ends with noncontaminated feed and feed ingredients will also be investigated. This group intends to coordinate a broad consortium of researchers and have a multi-institutional plan for related research and surveys soon.
USDA Also Engaging in Review of Potential Risks of Feed Contamination
USDA-APHIS is also interested in feed and feed ingredients as potential pathways of pathogen transmission. APHIS intends to conduct a critical examination of research through literature review on the potential for feed ingredients to introduce certain viral diseases of swine such as FMD, CSF and ASF. In addition, a group of technical experts will be engaged to collect and review existing intelligence on the topic of the potential risks of swine disease introduction through non-animal origin feed ingredients.
In 2018, SHIC’s Plan of Work includes several projects specifically related to feed contamination mitigation. SHIC resources, as well as the significant collective expertise of researchers from several universities and private enterprise, are being marshalled to examine the role of feed and feed ingredients as sources for contamination with swine disease. SHIC will be reviewing and publishing results regularly in its mission to safeguard the health of the US swine herd.
Funded by America’s pork producers to protect and enhance the health of the US swine herd, the Swine Health Information Center focuses its efforts on prevention, preparedness, and response. As a conduit of information and research, SHIC encourages sharing of its publications and research for the benefit of swine health. Forward, reprint, and quote SHIC material freely. For more information, visit https://www.swinehealth.org or contact Dr. Paul Sundberg at [email protected].