US researchers track pathogen survival in swine feed

By Aerin Einstein-Curtis contact

- Last updated on GMT

© iStock
© iStock
Feed or feed ingredients may offer viral pathogens access to US farmed swine, say researchers.

The Swine Health Information Center, funded through a one-time investment of swine checkoff dollars, has been working with South Dakota State University and Pipestone Applied Research to track the survival of pathogens in feed or feed ingredients as a way to better understand the risks presented, said Paul Sundberg, executive director.  

“The heart of the mission is to monitor diseases, domestic and foreign with the goal of being better able to predict the next thing that is going to be an industry issue,”​ he told FeedNavigator. The point is to learn from past lapses when diseases, like PEDV, Porcine Delta-Coronavirus and Seneca Virus A, present in other countries and spread to the US.

The team has released its preliminary findings​ regarding the role feed ingredients could play in the spread of diseases expected to cause production and economic losses for the swine industry, he said.

“The goal is to learn from those efforts and do better,”​ he said. The process includes monitoring what pathogens are present in other countries and improving understanding of what represents a risk to producers in the US.

“If we showed that PEDV could potentially be in feed ingredients in China [coming] to the US, what else should we be paying attention to?”​ said Sundberg. “This lets us help define or uncover potential risks – that was the goal.”

Another goal of the project is to improve readiness before another outbreak happens, he said. “What we will do is identify what we’re at risk of, and be better prepared to respond more quickly and more efficiently,”​ he added.

Tracking disease in feed

In the study, researchers identified a series of viral pathogens as significant risks to the US swine industry, said the research team in the whitepaper.

Diseases examined included porcine reproductive and respiratory syndrome virus (PRRSV) 174, porcine circovirus, African swine fever virus, influenza A, virus of swine H1N1 and vesicular stomatitis virus, they said. Pathogens studied through the use of a surrogate virus included foot and mouth disease virus, classical swine fever virus, pseudorabies virus, Nipah virus, swine vesicular disease virus and vesicular exanthema virus.

Those diseases or specified surrogate viruses were added to feed ingredients like organic and conventional soybean meal, soy oil cake, DDGs, lysine, choline, vitamin D, sausage casings and multiple pet foods and were incubated for 37 days, the group said. The time-period and environmental conditions for the samples were designed to mimic the transport of ingredients from China or Eastern Europe, depending on disease, to the Midwest.

Samples were tested for the presence of viral activity and viability using virus isolation and, when necessary, swine bioassay, they said.

Soy products, lysine, choline and vitamin D all were found to harbor live versions of different viruses at the end of the trial period, said the researchers. Some of the pathogens that survived the period included Seneca virus A (surrogate virus for foot and mouth disease virus), bovine herpesvirus-1 (as a surrogate for pseudorabies virus) feline calicivirus (a surrogate for vesicular exanthema virus) and PRRSV 174.

PRRSV was able to survive in both soybean meal and DDGs, they said. Several viruses are still being evaluated.

There were few expectations going into the trial, because the questions posed had not been asked before, said Sundberg. But, the variability found between what viruses survived and in which ingredients lent credibility to the results.

However, one unexpected finding was that all the positive controls, or samples of the viruses in growth mediums that were not feed ingredients, died, he said. “There must be something in those feed components that is protective of the viruses that supports it through the transport,”​ he said.

Ongoing efforts

The group is in the midst of work examining different types of mitigation strategies, said Sundberg. Preliminary results are expected to be available in the next several months

“The next step is to study the effectiveness of different mitigation products, to scrub the feed of the viruses, to neutralize them or there may be physical mitigations as well,”​ he said. “We don’t know about the effectiveness of pelleting or holding feed or feed components for a period of time under certain conditions – there is a lot of research that needs to be done there.”

Another aspect of identifying mitigating practices will be to examine procedures for use at a feed mill to mitigate the risk. he said.

The goal of the effort is to be able to offer producers options of how to manage risk, instead of only alerting them to the risk potential, he said.

The group also is working with researchers from Kansas State University, said Sundberg. “This effort with Kansas State is to do that research in a laboratory where you can use the pathogen itself instead of the surrogate,” ​he added.    

Although the work started looking at diseases for the swine industry, the project carries wider implications for producers of other animals, he said.

“If this model correctly identifies risk, and we think that’s the case, there are risks to others as well,”​ he said. “There are risks to animal agriculture in the US through feed importation.”

Steps to take

The team is working on mitigation strategies, said Sundberg. However, in the interim, producers can review their production and risk tolerance.

“One of the questions is should we start, as an industry, to consider importing products based on country status for disease, rather than least cost rations?” ​He asked. “That’s something that needs to have a thoughtful discussion, not something that producers should rush out and do.”

The discussion needs to examine what can be done to limit the risk potential in imported feed ingredients, he said. “Probably one of the best things they can do is talk to their feed network and suppliers – ask about the source of the feed components, and the quality control within that source,”​ he added.

“We don’t have any standards on which they should act, but having that discussion at least starts that conversation and awareness that we’ve got to all pay attention to,”​ he said. “It isn’t only a producer issue, or a veterinarian issue, it’s a collaborative issue.”

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