April 24, 2019
A feed mill that routinely works with Kansas State University’s Feed Mill Biosecurity Audit program recently contacted Cassie Jones with an issue. Since the mill is part of KSU’s routine biosecurity sampling, the associate professor had recently swabbed the facility and provided the staff with feedback from the testing on their highest areas for biosecurity risk, specifically the floor of the receiving area and workers’ shoes.
A couple months had passed since that visit, when the manager called Jones with news that two sow farms they work with had broken with delta coronavirus and Seneca Valley virus simultaneously. Both farms had implicated the mill, because it was the only central point that could have possibly connected them.
Jones sent in the retained samples from her previous visit for further diagnostics, and indeed, both delta coronavirus and SVV were present. Both farms had had delta coronavirus before, but had never had a reported SVV break. It was found in the mill, though, before it was found on the farm.
“I want to be careful about how we interpret that,” Jones says. “It doesn’t necessarily mean it definitely came from the mill, but it does tell us there is risk in the area; and where they had an issue on-farm, one of the earliest locations that was detected, or the earliest-risk entry points, was the mill.”
This particular mill is one of a dozen integrator, toll and commercial mills that uses KSU’s Feed Mill Biosecurity Audit program. Manufacturing anywhere from 200 tons to 16,000 tons of swine feed per week, the facilities stretch from Colorado to North Carolina and everywhere in between. Eight other mills have invited the research team in to do an initial swab, and additional mills have been contacting the team with requests.
“We want to have the data available and to make decisions as researchers, but we also want producers and the swine industry to be actively engaged in doing this, whether that might be on their own — or if they may take us up on our offer to help participate and lead some of this effort,” Jones says.
PEDV and pet food
Jones says the concerted effort really began during the height of the porcine epidemic diarrhea virus in 2013 and 2014, when KSU started researching ways to help prevent feed from being a vector of disease transmission. Through its Cargill Feed Safety Research Center, the university began work inoculating feed with PEDV and then examining what could be done to mitigate the virus and reduce any activity in the feed once it was infected intentionally.
During that process, the KSU researchers also started to collect environmental swabs to get a better understanding of how the virus can be spread throughout a facility. Jones says that idea stemmed from the pet food manufacturing industry.
“A lot of what we have learned about how to assess biosecurity and personnel compliance has really come from interactions with the pet food industry, because they are light years ahead of us as they have worked to control Salmonella, especially in any locations after extrusion,” Jones says.
After collecting the environmental swabs, Jones says the researchers were astounded by the amount of contamination all over the facility.
“It seems that almost every swab we took — and we took hundreds — was PEDV-positive,” Jones says. “Every wall and floor went positive with PEDV as soon as we introduced it in the manufacturing environment.”
Prior to this, KSU had focused its efforts on disease transmission through ingredients, mud and fecal material. Now the researchers had proof; the virus was able to be spread through dust.
Around that same time, the university received a research grant from the National Pork Board to study how Salmonella spreads throughout feed and the feed supply chain. While Salmonella is not known to be a substantial hazard in swine feed, Jones says the study was designed to characterize and confirm that. The objective of the study was to investigate Salmonella presence in different feed mills across the United States. Eleven facilities were selected in eight states, and 12 sites were sampled within each feed mill.
The KSU researchers once again turned to the pet food industry as they used Enterobacteriaceae as an indicator. A family of bacteria, EBAC includes both nonpathogenic and pathogenic genera, including Salmonella and E. coli. Research has demonstrated that the presence of EBAC is indicative of overall hygiene. The surveillance method is commonly applied in the human food and pet food industries but
is just beginning to see application in livestock diets.
The total number of environmental samples collected was 237: 66% were culture-positive and 13.1% were polymerase chain reaction-positive. All sampled feed mills had at least one culture-positive site, and following production flow, the number of positive samples decreased from ingredient receiving to final product. The researchers concluded that these preliminary results demonstrate the presence of Salmonella in selected United States feed mills and suggest the mills’ potential role as a vehicle for pathogen transmission and spread into the food production chain.
The research also helped to pinpoint areas within feed mills that were at higher risk for disease transmission.
Baseline and beyond
In 2017, KSU formally launched the Feed Mill Biosecurity Audit program. During an audit, the team takes about 10 swabs at different locations around the mill, such as receiving crates, fat intake inlets, hallways, floors and desks. A long cotton swab, sponge or gauze pad is used to swab a 10-cm square to ensure accurate representation and consistency each time.
“Using EBAC levels and going into feed mills, we can establish a baseline level and help identify areas where they may have a higher risk for virus entry throughout the facility, or compared to other feed mills,” Jones says. “We always start with one sample of feed, and the rest are all environmental samples. So, that gives us our baseline as we look at what is actually getting into the feed, but also people and vehicle movement on the farm.”
Through their testing the researchers have found more often the feed itself has a relatively low level of pathogen in it, while massive amounts of EBAC have been detected on workers’ shoes, on the floors of the receiving pit or on the floors of the control room or manufacturing area.
“Which really helps us understand, yes, we have to be diligent about ingredients, particularly with foreign animal disease; but simultaneously there are a number of things we can do to help minimize disease transmission, either through ingredients or by people walking through the feed mill, having the feed mill floors being a source for contamination into a mill as well,” Jones says. “I think it tells the story that we really need to be careful where these people are walking. We have boot covers, but there are times where we become less diligent. So, what are some things we can do in the mill, so those boots never get contaminated in the first place — or if they are, they don’t spread that contamination to another farm?”
While the EBAC testing is relatively inexpensive at $10 per swab and provides a baseline level for biosecurity and hygiene, the KSU team is now beginning to look at swabbing for other viruses.
“Is EBAC the best? Is rotavirus better?” Jones says. “How do they correlate with PEDV, Seneca, delta corona virus — and how do they all work through a feed mill system?”
The audits have also proven there’s more than meets the eye when swabbing. Normally, the dirty areas have higher EBAC, but not always. Sometimes areas in the mill that look clean can carry EBAC or other pathogens.
“Just because we leave something off or blow it down and we don’t have dust accumulation at that time, it doesn’t necessarily mean that it is not a high-risk pathogen area,” Jones says. “We are looking beyond just dirt and grime; we are looking even into clean facilities for where are the sites where we have accumulation of biosecurity risks over time.”
While the auditing program is still in its early stages, Jones says the feed mill staff the researchers work with are much more conscientious of the people they allow in, and where they allow people to walk.
“Typically, the first time we go swab a mill, truck drivers are normally allowed to use the break room in these facilities,” Jones says. “By the second time that we go there, they are not allowed to go in there anymore because we have found really high levels in the break room or the hallways.”
For those areas where traffic can’t be minimized, the KSU researchers have advised mills to starting using a dry disinfection powder on the floors — another idea they picked up from the pet food industry.
“If you know that is kind of an area of frequent cross-contamination, we will have people lay down some of that dry powder there, and it will help reduce bacteria risks and risks of pathogens at that point,” Jones says.
She has also been encouraging the mills to consider having employees keep a separate set of shoes at the mill and to use a Danish entry system, with a bench with two sets of shoes on each side.
“That is something that I really think we need to be doing,” Jones says. “When we look at some of the early data on PEDV, we want to minimize the amount of virus that could possibly come into these mills, and what our data continues to point to is the floors and the workers’ shoes that continue to be an issue at mills.”
3 biosecurity hurdles
To put the feed mill biosecurity protocol into perspective, Jones says she tells producers it’s really about eliminating the hurdles.
“Obviously we have to keep bad things out, whether we are talking about foreign animal disease or talking about high-risk ingredients or talking about people that have no reason to be there; the first goal of biosecurity is to keep high-risk materials out,” Jones says. “I think of these frequently as hurdles, so that you are cutting hurdles out so the pathogen doesn’t go from wherever it started into our finished feed.”
Keeping out high-risk ingredients should be the first hurdle, followed by moving biosecurity practices from the farm to the mill. As farm owners and managers routinely control vehicle traffic, foot traffic and pests, Jones says those efforts need to be extended to the feed facilities.
“We are doing all those things actively on-farm and have been for 15 to 20 years, so if you think that is important enough to control foot or vehicle traffic on-farm, extend that exact same principle into your mill,” Jones says.
The third and last hurdle is mitigation. If a disease challenge does come in, or if the audit finds opportunities for biosecurity improvements, what can be done to fix that? Jones says mitigation could involve procedures such as cleaning up areas and using dry powders, or adding feed additives such as medium-chain fatty acids or formaldehyde-based products.
“We need to first keep out high risk, extend that biosecurity from farm to feed mill, and then consider mitigation activities to make sure you have a final step in case it fails,” Jones says.
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