23 July 2019- The concentration of vitamin production in China over the last two decades has been swift and thorough. Today, China manufactures more than half of the world’s supply of every vitamin except vitamins A and B3 (niacin). For biotin, folic acid, and vitamin B12, 100% of world production is in China.

Dr. Jerry Shurson
Professor, Department of Animal Science
University of Minnesota

This dependence has added to the anguish around the outbreak of African swine fever. Questions are being asked: Should I quarantine my incoming feed additives? Do carriers used in some formulations represent an entry-point for animal-borne diseases? What about gelatin? Is there any way to kill viruses in my feed that won’t inactivate my vitamins? These are some of the issues Dr. Jerry Shurson and Dr. Pedro Urriola of the University of Minnesota cover in their recent report, Understanding the vitamin supply chain and relative risk of transmission of foreign animal disease. In their words, “the risk of ASFv or other Foreign Animal Diseases (FAD) being introduced from China into the US through vitamin imports appears to be low, but the impact of introduction is high.” Dr. Shurson elaborated on those conclusions in a conversation with Feedinfo.

A unique and little-understood virus

The report cites work by Niederwerder et. al. this year which demonstrated that the virus has a very low minimum infectious dose, meaning that relatively few viable viruses in a sample of feed will be enough to infect the animal. Unfortunately, those hoping to keep the ASFv out of the feed chain are working at a bit of a disadvantage. “The African swine fever virus is very unique because it is a double-stranded DNA virus, which is quite different from the single-stranded RNA viruses we have worked with. It is also a very resilient virus and has the ability to repair itself,” Dr. Shurson reveals. This makes it distinct compared to other viral pathogens that the industry has battled with, such as PEDv.

Particularly in light of the virus’s ability to repair itself, Dr. Shurson and his colleagues warn that it is problematic to extrapolate from existing knowledge on other pathogens and to assume that the same mitigation techniques will work. “[Maybe] you could destroy the capsid or receptors, which we are typically able to do with various mitigation treatments for single-strain RNA viruses… [but] for this virus we don’t know if destroying some of these components of the virus structure will, in effect, make it less able to infect pigs if it still is present in feed even after a mitigation has occurred,” he acknowledges.

One of the primary reasons for this troubling absence of information, according to Dr. Shurson, is the fact that experimentation on the ASF virus was limited by the lack of a surrogate virus that could be manipulated safely by many labs. “There are only maybe 3-4 laboratories in the world…that have the biosecurity procedures in place to allow research on a dangerous virus like African swine fever virus,” he asserts. Dr. Shurson is optimistic about the potential of recent work by Dr. Declan Schroeder (also at the University of Minnesota) who has reportedly identified a virus present in microalgae which bears most of the same characteristic as found in the ASF virus, but which poses no risk to humans, pigs, and other animals, and which can thus be used safely in a laboratory setting to try and answer some of these questions. “We’re in the process of trying to initiate research using that virus as a surrogate, to start getting the information that we need on mitigation strategies and activation kinetics that then can be used to conduct formal risk assessment analysis,” he recounts.

However, until more information is available, more or less the only way to rule out the possibility of ASF virus in feed ingredients is to be extremely vigilant that no opportunities for contamination occur. This is even more critical when it comes to vitamins, Dr. Shurson notes, because the “obvious” options for mitigation would deteriorate many vitamins. “Unlike other nutrients, vitamins are sensitive to oxygen, light, heat, pH, and transition metals, such as iron and copper, that cause loss in vitamin potency … Therefore, use of mitigation strategies that have been shown to be effective for PEDv, such as additives, pH, and thermal treatment will likely reduce vitamin bioavailability to varying amounts, even if they are effective in inactivating ASFv.” Extended hold times are correspondingly problematic for these particular additives: “Note that the fat soluble vitamins (A, D, E, and K) and vitamin C (ascorbic acid) are much more susceptible to vitamin potency losses (decreased retention) over extended storage than the B vitamins. Therefore, although specific holding times for vitamin containing premixes and feeds may be effective for inactivating ASFv if it is present, it could also lead to reduced vitamin potency and nutritional value, depending on the environmental temperatures during the holding time.”

At the vitamin manufacturing plant

With effective options for treating ASFv contamination in vitamins currently next to nonexistent, the vitamin manufacturing and shipping chains must be scrutinized carefully to ensure the additives never have the chance to become contaminated. On this front, heat-intensive processes provide the report authors some hope of a largely virus-free product. Although knowledge of the necessary conditions to inactivate the ASF virus is not yet available, the report observes “the time, temperature, and pH conditions used during the vitamin manufacturing process may be adequate to inactivate ASFv and other viruses if they are present.”

Similarly, the authors point out that the heat required in the production and processing of gelatin—derived from pork skins and used to stabilize vitamins A and D3—likely kills viruses as well, but they are careful to note that processes will vary amongst producers, so this is certainly a point in the chain that requires careful surveillance.

The same is also true of carriers; while most vitamins are shipped over as “straights” in as pure a form as possible, then blended with a carrier such as rice hulls to make premix once in North America, some—most notably choline chloride— tend to be blended with a carrier such as ground corn cobs while still in China. While not all choline chloride manufacturers are using corn cob carriers (preferring carriers such as silica) and still others visit and audit their suppliers to ensure that the carrier underwent a killing step, the report points out that “the origin and specific processes used to produce ground corn cobs as a carrier for choline chloride are unknown at this time, and need to be investigated as a potential risk factor for virus transmission.” Both the use of gelatin and the use of ground corn cobs are considered by the report authors to be among the 4 potential risk factors for ASF virus contamination in the vitamin supply chain.

Quality assurance: customers must ask questions

On the question of certifications for quality assurance and safety, there are also a mix of positives and negatives. On the positive side, there is no distinction between the production of feed grade vitamins and those destined for human consumption, meaning that hygiene standards are strict and exacting. On the negative side, compliance with certifications schemes is often voluntary, and may or may not be taken seriously by the company: “the types and use of quality assurance programs vary among Chinese vitamin manufacturers because the Chinese government considers them to be voluntary. As a result, some companies may claim that they are compliant with certifications for marketing purposes, but do not put much serious effort into actual implementation or compliance,” says the report.

Of course, the report is also quick to point out that reputable vitamin manufacturers and the importers serving western markets have robust quality assurance and quality control programs in order to meet the strict standards of customers, and are capable of providing documentation of their Good Manufacturing Practices. Probably the most important recommendation of the report is that customers should ask questions of their suppliers; purchasing from “unconventional” brokers or traders who do not provide documentation of country of origin, quality assurance, and sanitary transport is number one on the report’s summary of potential risk factors for transmitting ASF virus through the vitamin supply chain.

Importantly, customers can also leverage their influence to demand higher standards. The report gives examples of voluntary biosecurity commitments implemented by some vitamin manufacturers in an attempt to lessen the risk of ASF contamination, including requirements that employees do not also work on farms or own/breed their own swine, manufacturing facilities do not also house animals, and work clothes do not come into contact with meat (including employee meals). Dr. Shurson makes clear to Feedinfo that these sorts of compacts came about not because of any obligations imposed by quality control certification schemes or regulators, but rather from negotiations with clients worried about the ASF issue. “Outside of the general certification schemes that are used widely throughout the global feed industry, the biosecurity piece of all this, which is what everybody’s most interested in, is pretty much voluntary, driven by partnerships, customer demands, requests from pork producers wanting more knowledge and descriptions of how these things are produced and transported. That’s not coordinated, that’s, shall we say, à la carte, and very commerce- and relationship-specific.”

Indeed, Dr. Shurson goes on to explain, the ASF outbreaks in China have made visible a white space in quality control certification: there are, in fact, no standards which address whether processes which can react to specific pathogens are being adhered to. “FamiQS, and HACCP, and ISO, and Kosher, and Halal…these are all good and have very important purposes, but remember that none of those have any kind of biosecurity designation or certification program in place specific for viruses,” he states. Drs. Shurson and Urriola are involved in collaborating with a major feed industry company to develop a template for a supplementary biosecurity module which can be added on to existing quality certification programs in situations of high risk for viral contamination, and which can be dropped when not needed. A well-designed one would be relevant not just for the current ASF outbreak, but would be adaptable for potential future pathogens. “The topic of the day is African Swine Fever, but there are many other foreign animal diseases lurking in the shadows that could be pretty devastating to any country that is free of them at this point; we’re trying to keep a broader perspective of other foreign animal diseases as we go through this process,” states Dr. Shurson.

Keep perspective

While vigilance is indeed in order, Dr. Shurson insists that the risk of contamination entering via the feed supply chain is probably quite low. He recalls that there is evidence showing that viruses could theoretically survive in selected feed ingredients, including some vitamins, during a transoceanic voyage, but this does not mean that virus is actually present in feed ingredients in the first place. “We don’t know. Nobody has done the sampling to test for this specific virus because we don’t have an assay to use to definitively say ‘we did a PCR and found [ASF] DNA, RNA, present in x, y, & z samples.’”

This is especially true in light of the risks posed by other vectors. “[A] large number of people are coming in from endemic countries around the world to ASF-free countries, like the US, inadvertently or purposefully bringing food products in with their luggage. Those kinds of things to me represent a much greater risk factor.” Non-vitamin feed ingredients and pet food may also pose a risk that must not be underestimated. And, of course, there are those factors nobody sees coming until they arrive. “Someone a couple days ago brought up the fact that soybean meal may be imported for use in organic fertilizers. So we need to remind ourselves to think more broadly and not necessarily just focus on the feed supply chain, but we need a better understanding of the multiple uses of various imported products and where they’re going…we have to be aware of those [applications].”