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Research examines virus survivability in overseas transport
The US pork industry imports 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. Researchers from South Dakota State University, Pipestone Applied Research (PAR), and Kansas State University collaborated on the work.
Dr. Paul Sundberg, SHIC executive director, said, “This is foundational research. This project identified a new avenue through which we may be transporting pathogens around the country and the world.” Further investigation of potential threats posed by virus-contaminated feed ingredients and how to mitigate them will be a focus for SHIC in 2018.
The feed transmission study was published in the March 20, 2018, edition of PLOS ONE, a peer-reviewed open access scientific journal. Their website states, “PLOS ONE accepts scientifically rigorous research, regardless of novelty. The journal’s publication criteria are based on high ethical standards and the rigor of the methodology and conclusions reported.”
“This research gives us a model to uncover potential pathways for pathogen transport,” Dr. Sundberg stated. “Publishing the research in a peer-reviewed journal is extremely important. We want scientists to scrutinize it, repeat it and give constructive criticism. This underscores the importance and the credibility of the results and increases confidence in the outcomes.” Dr. Scott Dee, Pipestone Applied Research, said agencies, such as the U.S. Department of Agriculture and the Centers for Disease Control and Prevention, have shown interest.
“The findings of this study show that feed biosecurity should be a major priority for pork producers and ultimately, the livestock industry,” said Dr. Diego Diel. He and his team at the South Dakota Animal Disease Research and Diagnostic Laboratory (ADRDL) assessed the ability of 10 viruses to survive the 37-day journey from Beijing, China, to Des Moines, Iowa. Dr. Dee said, “For the first time, we have data to support that certain feed ingredients might be risk factors for moving viruses between farms and around the world.”
Kansas State University, which has a Level 3 biosecurity laboratory, also evaluated the ability of African swine fever virus to survive the 30-day trip from Warsaw, Poland, to Des Moines, under the direction of Dr. Megan Niederwerder. They also confirmed the results from using surrogates in the ADRDL/PAR portion of the project by directly testing CSF and PRV under identical conditions in their biosecure laboratory.
In previous work, Dr. Dee and ADRDL researchers discovered that porcine epidemic diarrhea virus (PEDV) can survive the simulated trip from Beijing to Des Moines in five feed ingredients—vitamin D, lysine, choline and organic and conventional soybean meal. That National Pork Board-funded research led to this larger study, which is supported by SHIC.
Identifying High-Risk Ingredients
Dr. Dee worked with a colleague at the Lincoln Memorial University College of Veterinary Sciences to expand the list of ingredients beyond those in the PEDV study. The researchers added soy cake and dried distillers grain solids (DDGS), moist and dry dog food, and moist cat food. Because the U.S. also imports sausage casings, a product of pork origin, from Asia, the researchers also added this product to the most recent study.
“We’re in a global economy; people and products are moving around the world,” Dr. Sundberg said. More than 47,000 tons of imported feed ingredients arrived in San Francisco from China in 2016, according to the International Trade Commission Harmonized Tariff Schedule.
Six viruses survived in conventional soybean meal, while only two did so in organic soybean meal. Conventional soybean meal is treated with hexane, while the organic soybean meal was not, Dr. Dee explained. Because of the processing method used, the organic meal tested had a high fat content and lower protein level. “Those ingredients with higher protein levels seemed to be more conducive to virus survival,” he said.
Pinpointing Key Viruses
A total of 11 viruses were studied: foot-and-mouth disease, classical swine fever, African swine fever, influenza A, pseudorabies virus, Nipah virus, porcine reproductive and respiratory syndrome, swine vesicular disease, vesicular stomatitis, porcine circovirus type 2, and vesicular exanthema of swine. Due to the inability to work with certain target pathogens, surrogate viruses were used to study closely related and structurally similar viruses.
“Certain ingredients seem to provide an ideal matrix for virus survival, and our study identified some of the high risk combinations of viruses and ingredients,” Dr. Diel explained. The SDSU team found viable Senecavirus A, the surrogate for foot-and-mouth disease, survived in all the ingredients except organic soybean meal. In addition, porcine sapelovirus, a surrogate for swine vesicular disease, survived in all ingredients except DDGS and choline.
The researchers also found that PRRSV can survive the simulated trip from China and it did so in conventional soybean meal and DDGS. “That was really surprising because PRRSV is quite unstable,” Dr. Dee said.
“Though the original goal was to assess potential for transboundary movement, there are also implications for pathogen transport at the regional or national level,” Dr. Diel said.
In conclusion, Dr. Sundberg said, “We all need to consider the implications of this research and then to understand if this potential transport could lead to transmission to animals and what we need to do next. We must work together with government agencies and the feed industry to protect U.S. meat protein agriculture.”
Swine Health Information Center (SHIC)-funded research about the potential for feed and feed ingredients to harbor and transport viral pathogens launched several related projects on mitigation and testing.
Testing Feed Additives for Risk Mitigation Potential
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), porcine reproductive respiratory syndrome virus, 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.
Summary
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.
Swine Health Information Center (SHIC) Board Member Dr. Brett Kaysen of Colorado resigned his position as the representative from National Pork Board last month due to a career change. Gene Noem of Iowa will now fill the National Pork Board representative role on the SHIC Board of Directors.
“SHIC is filling an information gap for the livestock industry, in particular the swine industry,” Noem remarked. “You don’t have to look very far back in history to realize unknown and foreign animal disease can really impact us in a way we really haven’t imagined. Unless we’re prepared, there’s potential to suffer a disastrous consequence.”
Noem, whose entire professional career has been spent in the pork industry, recognizes the value and contribution of SHIC to the entire industry. He has seen the benefit of international collaborations and the industry’s ability to recognize and respond to disease.
“That is what SHIC is doing – creating international collaborations. These will help us understand better how those threats and diseases can move. Does it come here through feed, animals, or other vectors like people or equipment? Once it is here, what do we do, how do we react, how do we diagnose? SHIC creates infrastructure to quickly respond because we have studied it,” he stated.
Noem has served on the National Pork Board for two years and served on many committees at both the national and state level. He has been a member of the Iowa Pork Producers Association Board for five years as well. Noem worked for PIC and Smithfield for 20 years before going to work for Reicks View Farms. He is also a contract grower, raising pigs on his own hog farms in Iowa.
The second Swine Health Information Center (SHIC) domestic disease monitoring report includes veterinary diagnostic laboratory (VDL) information about porcine reproductive and respiratory syndrome virus (PRRSV), and porcine enteric coronavirus (PEDV) testing, documents an increased porcine deltacoronavirus (PDCoV) detection, as well as news on an increase in central nervous system (CNS) tissue submission.
This VDL collaborative project is aided by an advisory group to help give context to the data and interpret it. The goal is to aggregate swine diagnostic data from participating reporting VDLs then present it in an intuitive format via shared reports and web dashboards. The current report uses Iowa State University VDL information to refine the template with plans to add additional VDLs as soon as possible.
Per the report, sequences requested for PRRSV in the first three months of 2018 were up 16 percent over the same time period in 2017, suggesting increased interest in better characterizing viruses during outbreaks. Data further show a significant increase in percentage of cases testing positive for PRRSV by rPT-PCR, which may be an indication of increased PRRSV activity this winter.
Similarly, the report reflects PEDV information consistent with ongoing, expected incidence of positive testing and anecdotal data on an increase in PDCoV detection. The advisory group’s perception is that the PDCoV increase may be related to clinical disease in suckling pigs, as well as non-clinical, incidental, PDCoV detection in finishing-age pigs.
Information on the incidence of CNS pathogens are based on their identification in tissues from clinical CNS cases. Data show a significant increase in submission of tissues related to clinical CNS signs, again consistent with reports from the field on increased CNS cases.
SHIC’s domestic disease monitoring report describes dynamics of disease detection by pathogen over time, specimen, age group, and geographical space. These reports, as well as SHIC’s global disease monitoring reports, are posted on the SHIC website: www.swinehealth.org and accessible from the homepage navigation menu under Disease Monitoring.
The Swine Health Information Center (SHIC) posted a new global swine disease monitoring report on April 3, 2018, with information on foot-and-mouth disease (FMD) activity in China and Korea presenting the highest concern.
From the report:
This past month saw some more activity of FMD in China and Korea. In both countries, there is extensive vaccination for the disease, but the efficacy of the vaccine and the compliance to the vaccination regime can vary widely. The Korean outbreak was the first farm affected in Korea since February 2017. Though China reports sporadic cases, a case where a herd of 1200 sheep affected in the Henan province of China raises additional concerns. Henan is a swine dense province, and this level of disease may have negative effects on the large producers in the area.
Currently, the SHIC global disease monitoring project is evaluating African swine fever, foot-and-mouth disease, and classical swine fever as the near real-time monitoring system is further refined. Subsequent reports will include information about additional, production-affecting diseases.
Experts reviewing the information use their expertise to score the relevance and importance of each incident to the U.S. pork industry. As conditions change, so does the relevance scoring. As part of the ongoing development of the report, collaborators are working on a system to enhance gathering of local information about international health events that may be considered of interest to US practitioners.
This monitoring system, funded by SHIC, was developed at the University of Minnesota using a private-public-academic partnership including collaboration with the USDA/APHIS Center for Epidemiology and Animal Health (USDA-CEAH). SHIC encourages feedback on the report; please share your thoughts on content, format, and suggestions to make it better. Email Dr. Sundberg at [email protected].
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