Determining the impact of commercial feed additives as potential porcine epidemic diarrhea virus mitigation strategies as determined by polymerase chain reaction analysis and bioassay()

Gebhardt, Jordan T; Woodworth, Jason C; Jones, Cassandra K; Tokach, Mike D; Gauger, Philip C; Main, Rodger G; Zhang, Jianqiang; Chen, Qi; DeRouchey, Joel M; Goodband, Robert D; Stark, Charles R; Bergstrom, Jon R; Bai, Jianfa; Dritz, Steve S

The very small quantity of virus necessary to cause infection has been determined in cell culture (Thomas et al., 2015) as well as in complete feed (Schumacher et al., 2016) . Such documentation provides support for field-based reports of potential infection using feed as a vehicle (Pasick et al., 2014; Bowman et al., 2015) by realization that such minute quantities of foreign material can be incorporated into feed-manufacturing facilities through improper biosecurity procedures as previously described (Cochrane et al., 2016b) . A significant spatial and spatial-temporal clustering pattern was documented with the initial PEDV epidemic beginning in 2013 (Alvarez et al., 2016) , suggesting indirect spread such as aerosols or fomites could be a likely explanation. However, it has been established that pathogens including PEDV and PDCoV can be found in feed-manufacturing facilities and equipment, including truck pedals and flooring (Greiner et al., 2016) . Thus, failure of proper biosecurity by feed delivery personnel can contaminate a feed-manufacturing facility and subsequent deposition of infectious material into swine production facilities may contribute to the spread of the virus. Feed manufacturing and delivery is a complex procedure and a high level of biosecurity in such process is critical to maintenance of high herd health, but establishing such procedures is complex and additional research and education efforts are necessary to fully understand the complexity and methods needed to minimize potential disease transmission events (Dewey et al., 2014) . Research evaluating a potential mechanism for introduction of viral pathogens into the United States through a transboundary transportation model using feed, various feed ingredients, and pork products has been described (Dee et al., 2018) . Such a model demonstrates the plausibility of viruses to survive the conditions that could be expected based on shipment across large geographic regions and provides important information regarding risk differences among viruses and shipped products such that future mitigation strategies can be tailored to specific virus and product. The use of cost-effective, readily implementable, and safe feed additives to minimize risk of disease transmission would be a very useful tool in addition to biosecurity practices.