17 June 2021 - Biosecurity is defined as “the set of practices carried out to prevent the introduction and spread of infectious agents in a herd.” These practices are essential in swine production, especially for highly infectious agents such as Porcine Reproductive and Respiratory Syndrome virus (PRRSv) or Porcine Epidemic Diarrhea virus (PEDv) or for any other bacteria and pathogens. Despite knowledge of the various ways in which the virus can be transmitted from one herd to another (e.g. via animals, feed, transport, air, and people), determining the most frequent ways in which the virus is transmitted in the field remains difficult.
Work continues, especially in the US, in the development of approaches to assess vulnerabilities at herd level related to virus transmission with an aim to enable producers to implement biosecurity practices to reduce or avoid the occurrence of outbreaks.
Dr. Derald Holtkamp of Iowa State University’s College of Veterinary Medicine has committed much of his life’s work to bio-exclusion — i.e. keeping pathogens from entering and infecting swine herds. He and fellow researchers have developed a process for disease outbreak investigations, designed to identify hazards that make farms vulnerable to the introduction of pathogens and prioritise biosecurity measures to address those hazards. Presenting at the recent North Central Avian Disease Conference, Dr. Holtkamp said the approach is based on the basics of epidemiology and Hazard Analysis Critical Control Points (HACCP), which looks at how pathogens are transmitted from one herd to another.
Dr. Derald Holtkamp
Feedinfo recently caught up with Dr. Holtkamp and asked him how his approach works and how it helps detect the most significant vulnerabilities on farms to determine where biosecurity control measures are most urgently needed. We also discussed what the global pandemic may change for on-farm biosecurity, as well as the preparedness of the US swine sector should African Swine Fever (ASF) ever break out on US soil.
The HACCP Approach
He argued that the industry’s current approach to biosecurity tends to be very much driven by the “flavour of the day,” in other words one specific area of animal production, like the potential role of feed in virus transmission, or that of livestock transport, rather than by a more holistic approach. He also stressed that every production system is going to be different and even every farm within a production system is going to be different when it comes to hazard analysis.
“It’s important that we step back and do a better job of assessing where these hazards are that are putting our farms at risk to the introduction of these viruses. We need to look at what are the most frequent causes and where are the vulnerabilities to pathogen introduction,” Dr. Holtkamp said.
“That's exactly why we're doing this, and the idea here is that once you do those assessments, it provides you with the information you need to then go in and prioritise where you need to have biosecurity control measures,” he added.
Hazard analysis can be done prospectively where investigators routinely go out and conduct their work on the farm. The other and most common hazard analysis is carried out right after an outbreak, as this enables investigators to look back at a herd and identify hazards during a specific time period when the virus was likely introduced. This is generally referred to as an “outbreak investigation”, which is conducted within two or three weeks after an outbreak has occurred, while memories are still fresh, so that everything that happened can be observed in the hope of knowing the exact time when the virus was introduced. Investigators also have other epidemiological information to work with.
Dr. Holtkamp explained that his team has a standard set of information that they gather or collect from the farm manager as well as from the herd veterinarian or others at the company being investigated. They then use the information to prepare an investigation form. It will have maps, satellite images of the site and its surrounding area, as well as any diagnostic information or sequencing information for viruses, etc. The on-farm assessment ensues, starting with a walkthrough and observation of general hygiene.
Commenting on this, Dr. Holtkamp said: “Generally we have a little introduction where we talk about the purpose of the investigation, and we emphasise that we are there not to cast blame on somebody but to identify hazards that we can then use to improve biosecurity control measures. The farm managers are there too, and our presence is in their best interest. They generally don't feel like they're being investigated. If ever they feel that way, you're not going to learn what actually happened.”
After the tour, the investigators go through the findings in the form guide which is organised by farm entry events (entry of semen, entry of employees, removal of weaned pigs…) And each one of those events has a set of potential carrying agents that may be contaminated or infected with virus.
“We want to understand all the details,” said Dr. Holtkamp. “The who, when, where and how all those activities occur. I consider that to be just the scaffolding because if it's a larger company involved, we may want to also investigate some specific areas such as the feed mill or truck wash facilities.”
Farms tend to use historical data and compare herd mortality patterns. However, asked what kind of progress has been made in terms of “real-time” animal health monitoring and rapid detection of virus-like symptoms in commercial herds and flocks, Dr. Holtkamp highlighted some of the work carried out at his department at Iowa State University involving machine learning type technologies and artificial intelligence, as well as tracking trial herds via oral fluid samples and PCR tests.
He believes that the scientific progress being made to identify animal health challenges early on will shape the future of animal monitoring and will prompt a more strategic and efficient use of diagnostics rather than doing them routinely. However, it remains very expensive.
“We will be able to better predict when these groups are going to perform and what their disease challenges will be,” he commented “I do think that's a feature which is going to change a lot in America.”
What COVID-19 Means for Biosecurity
Also moving forward, COVID-19 may have its silver linings. Of course, the pandemic has taken a severe toll on humanity and presented the agriculture industry with many challenges, but it did also have at least one benefit: giving the public an understanding of the concept of biosecurity. Dr. Holtkamp thinks a couple of things may have happened during the pandemic that have helped the work on farm biosecurity.
“One of those is the sudden mass awareness of people as major carrying agents,” he said, advocating for a more formal farm entry process to mitigate virus entry risk either before people arrive at the farm or as they as they enter.
Dr. Holtkamp added: “The other thing I think that maybe happened is simply raising awareness of how viruses are transmitted. The pandemic made everybody amateur epidemiologists. People have started paying attention to virus transmission, social distancing and wearing a mask, all of which are existing biosecurity control measures. I think people that work on swine farms can relate to that and better understand for instance why they must shower before entering the farm.”
The Iowa State University researcher also pointed out that there is a lot of discussion about the concept of layering.
“That's something we have talked about in the context of biosecurity and swine farms for a long time, but the idea that kind of came out again in the pandemic, where you socially distance and wear masks and don't go out if you're sick... All those things are layers that when you put them together, have some substantial benefit and each one by themselves you know, isn't perfect. But if you if you put them together, then all of a sudden, they are pretty effective,” Dr. Holtkamp said.
“There's actually a name for that, it’s called the ‘Swiss cheese model.’ Biosecurity control measures may have holes and none of those slices are perfect. But if you put enough slices of Swiss cheese together, they form a solid block. That's the idea of layering and I think people may have become more aware of that too.”
Dealing with the Eventuality of an ASF Outbreak in the US
ASF has caused significant pig losses around the world in places such as China, Asia, and sub-Saharan Africa, as well as within parts of Europe. In the US, the United States Department of Agriculture (USDA)’s Animal and Plant Health Inspection Service (APHIS) oversees the prevention, surveillance, and control of foreign animal diseases, including ASF.
However, in the words of the Food and Drug Administration (FDA) in a recent statement, “fortunately, ASF has never been found in the United States – and we want to keep it that way!”
We asked Dr. Holtkamp how prepared the US swine sector is from a biosecurity point-of-view for the eventuality of an outbreak of a new transmissible type of swine disease and/or a virus like ASF.
He said that there are a lot of efforts underway at national and sector level, the main coordinating parties being the USDA, the National Pork Board, the Swine Health Information Center (SHIC), and the American Association of Swine Veterinarians (AASV).
And prior to the pandemic (in September 2019), an industry-wide exercise coordinated by USDA and the World Organisation for Animal Health (OIE) simulating introduction of ASF virus took place, which in Dr. Holtkamp’s opinion “revealed a lot of gaps.” But was a “good first step to say ‘let’s get better prepared now.’”
Of course, since then, the government and the industry has been addressing the gaps. However, Dr. Holtkamp believes there is still a lot of work to do.
“If ASF gets on our soil, it still has to get to pigs in herds. I think the single best thing we can do to prepare as an industry is to improve our farm level biosecurity, because that's the last line of defense, our best weapon.”