Biosecurity is extremely important to keep African swine fever virus from commercial swine farms.

Tim Lundeen 1, Feedstuffs Editor

September 19, 2018

3 Min Read
ASF virus basics, potential risk mitigation addressed at Leman Conference
agnormark/iStock/Thinkstock

At the Allen D. Leman Swine Conference, hosted by the University of Minnesota, the topic everyone was discussing the most was African swine fever (ASF) and potential protocols to keep the virus out of North America.

In a "hot topics" session, Dr. Chris Oura from the University of the West Indies, and previously an ASF researcher at The Pirbright Institute in the U.K., discussed the virus itself, explaining that the ASF virus is large, complicated and very tough, with about 24 genotypes. He said the prevalent genotypes are the most variable in southern and eastern Africa in warthogs — in which the virus originated — and soft-bodied ticks, which is a intermediate host. Genotype II is the one currently spreading in Europe and China.

Oura explained that while most ASF genotypes are highly virulent, not all are. As the virus circulates, it can change over time to become moderately virulent or even non-virulent. If this happens, pigs infected with the virus but recover can become virus carriers, meaning there is a cocktail of ASF virus in the environment that is much more difficult to control. Oura said there is some evidence that some pigs in the affected region of Eastern Europe have been able to recover from ASF infection.

Oura reported that there is a lack of effective vaccines against the ASF virus because it is a large and complex virus with about 165 proteins, and most of those proteins are not well understood. Few groups have been involved in research because of the lack of a commercial market for a vaccine and because, until recently, the virus had only been found in areas of Africa that did not have commercial swine production.

The Pirbright Institute is the global ASF Reference Laboratory for the World Organization for Animal Health. Pirbright scientists are working to better understand how the virus evades the host’s immune system and how it is transmitted, which will aid the researchers’ ability to develop vaccines.

Oura concluded that for the U.S., the real risk of ASF if the virus appears in North America is through the interaction of backyard/outdoor pigs and the wild/feral swine that maintain virus in environment. Biosecurity is extremely important, and high levels of biosecurity can keep virus from getting into intensive hog production systems, Oura emphasized.

In a subsequent session, Leman Conference attendees heard about early research results may be used to enhance feed safety protocols to reduce the risk of ASF virus transmission as well as other foreign animal diseases and other viruses.

In the session coordinated by the Swine Health Information Center (SHIC), Jordan Gebhardt of Kansas State University said there is a "cascade of questions" to evaluate the risk of disease transmission through feed: (1) Is the feed/feed ingredient likely to get infected? (2) Will the infectious agent survive? (3) Will the agent still be infectious when the feed/feed ingredient is fed? (4) Can the contamination be prevented? and (5) How can the contamination be mitigated?

Mitigation steps could include ingredient quarantine; point-in-time measures such as dilution to below minimal infectious dose, irradiation, thermal treatment (these are prone to recontamination and altered product quality) or residual treatment with feed additives such as organic acids/alkalis, formaldehydes, medium-chain fatty acids and others, according to Gebhardt. He added that research is ongoing into these feed additives.

American Feed Industry Assn. vice president of public policy and education Leah Wilkinson told Leman Conference attendees that the feed industry is paying attention on viral contamination of feed and is trying to be transparent within and outside the industry, finding out what information is needed and how to disseminate that information in the best way.

She added that some proposed mitigation steps such as quarantines can be applied now, but the use of some feed additive products cannot currently be used as viral mitigants because they are not approved by the federal government for that claim or labeled for virus mitigation.

SHIC executive director Dr. Paul Sundberg concluded the discussion by noting that there are "a lot of other potential windows for foreign animal disease (including ASF) entry besides feed. We need to keep that in mind."

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