WASHINGTON, Sept. 30, 2015 – The viruses that appeared in the U.S. in the spring of 2013 and killed millions of piglets may have entered the country in so-called Flexible Intermediate Bulk Containers, essentially very big bags used to transport sand for flood control, soybeans and all kinds of bulk material, according to a USDA report.

The report, by the department’s Animal and Plant Health Inspection Service (APHIS), says evidence collected in its investigation suggests that the FIBCs could be potentially contaminated in their origin country and then reused after arrival in the U.S. The bags are designed for reuse and are not usually cleaned or disinfected between use in the U.S.

“If a contaminated FIBC was used to transport bulk feed or ingredients to the swine feed mill networks, a small bit of contaminated material could have been mixed into feed destined for many locations and spread the virus onto farms,” APHIS said in a release. Follow-up testing supports the hypothesis that the pathogens could easily remain stable through the time needed to travel to the U.S. and infect pigs, the agency said.

The first cases of the Swine Enteric Coronavirus Disease (SECD) were confirmed in the U.S. in the spring of 2013. The viruses, including the Porcine Epidemic Diarrhea virus (PEDv), quickly spread to swine farms throughout the country, killing millions of animals, including more than 7 million piglets. Hogs usually recovered from the gastrointestinal distress and dehydration caused by the viruses, which were most often fatal to pre-weaned piglets.

APHIS said it examined 17 potential “root cause” scenarios, including accidental or intentional introduction by people, contaminated feed supplements, and contaminated semen or germ plasm. The investigation did not uncover definite proof of any route of entry, the agency said, but a small number of scenarios were deemed plausible.

Among these, “the scenario that best fit the criteria for virus entry into the U.S. was virus spread through reuse” of FIBCs. Click here to see the entire 53-page report.

In its release, APHIS noted that it has been working with the states and the swine industry to slow the spread of the disease, including enhancing biosecurity measures. The agency also issued a Federal Order in June requiring the reporting of SECD cases to assist with tracking and understanding the viruses. The number of new cases has dropped dramatically in the past year.

APHIS said it has not able to identify a definitive source of the viruses identified in the U.S. However, the report pointed out that pathogenicity and genetic analysis of the viruses “are highly similar to those identified in China between 2010-2013.”

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