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Deadly Pig Virus May Have Sneaked Into US On Reusable Bags

How diseases cross borders can be a dark mystery. It’s never been clear, for instance, just how West Nile virus arrived in the United States in 1999. Researchers think they know why clusters of malaria cases occur around international airports, but no one has proved the hypothesis by catching an infected mosquito as it flies out of a plane’s cargo compartment.

So when piglets started dying in droves in the summer of 2013, from a rapidly spreading disease called porcine epidemic diarrhea virus (PEDv) that had never been seen in the United States before, animal health experts were baffled. In a frantic search for the source, epidemiologists investigated whether the pathogen had escaped from a laboratory, or been carried by migrating birds, or lurked in frozen semen taken from hogs in other countries. Was pig feed contaminated? Were feral swine carrying it? The virus was closely related to one found in China, and many of the ingredients in pig feed come from there. But the Chinese meat firm Shanghui was in the midst of buying Smithfield Foods; had a businessman unknowingly carried it around the world?

As the epidemic spread, millions of pigs died, more than 10 percent of the entire American herd. The US was virgin territory for the virus, which leapfrogged the country randomly and with wicked speed. It killed so many pigs that pork prices spiked, and it cost more than $1.8 billion to track and detect the disease, and to clean up infected areas and shore up the earnings of affected farms.

Two years later, after exhaustive studies, the US Department of Agriculture’s Animal and Plant Inspection Service says it has identified the vehicle that carried the virus across the world. The culprit was something so humble, it was easy to overlook: the giant woven bags that are used to transport feed ingredients across oceans, and then reused in the United States to carry mixed feed between feed mills and onto farms.

Until now, there have been no regulations governing the use, reuse or resale of the bags, the USDA said—and that includes any rules about cleaning or disinfecting them. So a bag that picked up contamination abroad, probably in China, could be moved in the US from port to wholesaler to feed mill to farms and on to other feed mills, disseminating virus as it went.

In their research, epidemiologists built an algorithm that would help them rule out less plausible possibilities and narrow down the cause. The USDA report says that, out of 17 possible explanations, only the giant bags—which can hold up to 3,000 pounds of material—tick every box. They could have been contaminated outside the US; they would have protected the virus in transit; they were moved around the country in a way that would rapidly disperse the pathogen; and they were carried onto farm properties, breaching biosecurity protections that farmers had set up.

FIBCs holding fertilizer on a French farm. Original: Wikimedia (CC)
FIBCs holding fertilizer on a French farm. Original: Wikimedia (CC)

The bags, called “Flexible Intermediate Bulk Containers,” or FIBCs (or GRVS, if you conduct business in French), are incredibly common in shipping. They are a huge business, with dozens of manufacturers and their own international trade show, and millions of them are used each year to move things that are heavy and dry: wood shavings, gravel, granular chemical compounds, vitamins, grains and pet food. They have big loop handles, so they are easy to tie closed, or to hoist with a forklift or a hook. They are stackable and stable, because they conform to the shape of what’s inside them; and rip-resistant and lightweight, because they are made of woven synthetic.

And, it turns out, they are accidentally well-constructed for giving a home to viruses. To keep from tearing, FIBCs are assembled with an outer layer and a lining. In tests, the USDA found that once a bag was contaminated—by particles of ingredients sifting through the inside, or tainted water soaking through the shell—the shield of the outer layer could protect the virus from sun, wind and temperatures for weeks.

That could explain something that people noted early on in the epidemic: Outbreaks seemed to have something to do with pig food. When investigators checked, though, they could not find any link among all the farms. There was no single person—no veterinarian or field technician or truck driver—who had visited every affected property. The farms did not feed the same food or use the same supplements or buy from the same companies. What investigators missed, until the report’s deep dive, was that almost every large pig farm in the country uses the same types of feed ingredients—and all the ingredients move along a transport chain that was polluted by the arrival of contaminated bags.

It’s not clear what happens next, though. If bags being transported into the US were contaminated in another country, that is outside the purview of US regulators. Inspections of imported food, even animal food, are required under US law, but the corps of inspectors is known to be understaffed. And import inspection might not even have detected virus lingering in minuscule amounts within the woven surfaces of the bags.

To prevent something similar happening again, the US could try regulating the reuse of the giant bags, which can stay in circulation for up to two years before wearing out, or could insist on cleaning and disinfection standards. Any of those would be disruptive to a complex global industry, and are unlikely to happen quickly. Until they do, the bags will serve as a unwelcome reminder of the subtle, unpredictable routes that diseases travel, and the need to be always on guard.

5 thoughts on “Deadly Pig Virus May Have Sneaked Into US On Reusable Bags

  1. These bags could also serve as a vector path for novel viruses that are able to hop from hogs to humans, and for prions (Mad Cow, Creutzfeld-Jacob) in noncompliant feed made from animal neural tissue.

    The reuse of containers is necessary for ecological reasons, but the failure to sanitize them is intolerable. We would not put up with milk or soda in glass bottles that were not washed during their trip through the bottling plant, or any other sort of food for human consumption that was packaged in unsanitary containers.

    The fact that infectious agents can be transmitted to and among livestock via these bags is bad enough; the potential for human infection raises this to a public health issue that should come within the purview of the CDC or even Homeland Security if one considers the bioterrorism risk.

    The impact on industry of a requirement to sanitize the bags, is no basis for allowing unsanitary containers to circulate. It should be straightforward to design a machine that can do the job effectively and at relatively low cost, and the costs of installing these machines and using them would be trivial by comparison to the cost of epidemics among livestock or humans.

  2. Perhaps they should really consider irradiating the bags on their way into the country with the food inside. Disinfection of surfaces like this are difficult at best to confirm. This is a wake-up call to the industries that receive any kind of food source from overseas. For livestock, pets or humans.

  3. I call BS on this. It was what, about 8 years ago when the “Mad Cow” disease scare tripled the price of beef. It’s been 8 years and the price of beef is still stratospheric, I guess mad cow disease is still running rampant, huh? A year or so later, it was a swine disease that killed all the piglets, tripling the price of pork. A year or so after that, the chicken ranchers tried their hand at it and lo and behold, if there wan’t a giant chicken disease that necessitated tripling the price of chicken.

    This is the food producers equivalent to the oil companies raising the price of gas in an instant because of one excuse or another (they really don’t matter, one is as good as another) and then never really lowering the price after the “situation” has passed. Sure there are porcine diseases out there, always have been. But when just the threat of it it is connived to use as an excuse to gouge the consumers, well, bubbly BS articles like this don’t impress me at all.

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