Weight of the evidence linking feed to an outbreak of porcine epidemic diarrhea in Canadian swine herds

Porcine epidemic diarrhea (PED) is a highly contagious disease of swine caused by the porcine epidemic diarrhea virus (PEDV), an Alphacoronavirus of the Coronaviridae family.1 Swine enteric coronavirus diseases (SECDs) have been known for decades, but PEDV was reported for the first time in Canada in January 2014, nine months after it was first discovered in the United States in May 2013. Even though genetic and phylogenetic analyses of three US PEDV strains suggest that they likely originated from China,2 the exact pathway for introduction has yet to be identified. A root cause investigation conducted by the United States Department of Agriculture Animal and Plant Health Inspection Services (USDAAPHIS) suggested that the use of flexible intermediate bulk containers, contaminated in the country of origin and reused in the United States for the transport of bulk feed or feed ingredients, could have been the source of introduction of SECD viruses into the United States, as well as contributing to their widespread introduction onto individual farms all over the country.3