DES MOINES, Iowa (AP) — A virus that killed more than 8 million baby pigs in 2013 and 2014 nearly matches the DNA of a virus found in China and was likely carried into the United States on reusable tote bags used in international trade, the U.S. Department of Agriculture said Wednesday.
A special investigation began last summer into the possible sources of the virus, known as porcine epidemic diarrhea. Nearly 10 percent of the nation's hog population was lost, severely reducing the supply of pork and sending bacon and pork chop prices to new records last year. The industry has worked to rebuild herds since then.
How the virus spread remains unknown, but many scenarios of how it arrived in the U.S. and spread were considered, including intentional infection, accident transmission by visitors from abroad and transmission of the virus via pet treats made in China. Investigators determined that the tote bags called Flexible Intermediate Bulk Containers "best fit the criteria established for entry into the United States, rapid and wide spread across the country, and introduction onto individual farms," according to Wednesday's report.
The woven, plastic fiber bags designed to ship between 1,000 pounds and 3,000 pounds were reused — making cross-contamination a possibility — and often not cleaned, the report said. Tests on the virus determined it could survive for several weeks within the protective weave of the bags.
Investigators said it is plausible the bags were contaminated with fertilizer, compost or wastewater from a farm before being shipped to the U.S.
Feed mills in the U.S. receive products and transport feed in the tote bags, allowing for potential cross-contamination. Some veterinarians working with farmers on the pig virus believed the feed supply may have been involved. The USDA recommended companies not reuse the bags or develop a way to sanitize them. The report points out that animal feed product handling policies have since changed.
Pork producers said they appreciated the effort to identify the cause of the disease, but remain uneasy that the USDA report was not definitive. The virus was believed to have first surfaced in April 2013 in Ohio and spread quickly to dozens of states, with the hardest hit being Iowa, Illinois, Minnesota and North Carolina.
"The investigation, however, was inconclusive, so a pathway is still open for the entry of other diseases such as foot-and-mouth disease," National Pork Producers Council spokesman Dave Warner said. "NPPC remains concerned about this gap in our system for protecting animal health."
The report also noted that pet treats including chicken jerky, pig ears and other products also are transported into the U.S. from China in the tote bags. The FDA and USDA investigated whether there was a connection between the pig virus and the hundreds of pet deaths from jerky treats imported from China in 2012 and 2013, but nothing was detected.