African swine fever is currently one of the most significant threats to worldwide swine production. ASF does not cause human disease. ASF is a reportable disease that has a devastating effect on the health of infected pigs. The closure of borders to trade can have a catastrophic effect on countries that rely on exporting a significant amount of their production. Preventing introduction of the virus into countries that are still free of the disease is therefore of primary importance. The global distribution of feed ingredients is one of many ways that this virus can move over very long distances.
Among the feed ingredients that were identified as higher risk, unprocessed grains and oilseeds (such as corn and soybeans) and their associated meals destined for livestock feed and which originate in countries that have reported cases of ASF in the last five years have been deemed the highest risk. The Canadian Food Inspection Agency is working with groups such as ANAC to develop risk reduction programs for feed ingredients imported from ASF infected countries. CFIA has also declared secondary control zones around major ports of entry and this provides authority to take steps to mitigate this risk. ANAC’s “National Biosecurity Guide for the Livestock and Poultry Feed Sector” which is now available, is designed to help the feed industry develop strong biosecurity protocols for the feed supply chain.
Dr. Megan Niederwerder at Kansas State University is leading a team that is adding scientific evidence that confirms how ASF could spread across borders via feed and feed ingredients. This research is carried out in the Biosecurity Research Institute, a biosafety level-3 facility, that has the capability of safely handling ASF. Their first study found that the ASF virus could survive in a simulated overseas feed shipment. This current study has helped to “connect the dots” by demonstrating that ASF virus can be transmitted from infected feed to the pig through the natural oral consumption of the contaminated feed and liquid.
The authors pointed out that proving the absence or presence of ASF virus in a batch of feed is difficult because the pockets of infection can be very small. It is not as simple as doing a viral detection test on suspect loads of feed. Sub-sample selection can make finding the ASF virus in a load of feed akin to “finding a needle in a hay stack”. Because pigs will consume an entire load of feed, however, finding the infection after it is fed to pigs is more of an eventuality. It is a bit more like “chewing on the entire hay stack until you bite down on the needle”. It’s going to happen if the needle is there!
The next research will focus on identifying ways to reduce or eliminate the ASF risk in feed and this will include evaluating the use of chemical additives, storage time, heat treatments or other steps
Take Home Message
ASF infection can occur via natural oral consumption of feed or water.
The “Connecting of The Dots” in a scientific way is continuing. The feed industry needs to develop strong feed import and biosecurity protocols as part of the best management practices for the supply chain.
Submitted by Doug MacDougald, DVM
Ref: Niederwerder MC, Stoian AMM, Rowland RRR, Dritz SS, Petrovan V, Constance LA, et al. Infectious dose of African swine fever virus when consumed naturally in liquid or feed. Emerg Infect Dis. 2019 May [date cited]. https://doi.org/10.3201/eid2505.181495