The European Commission has approved new rules aimed at limiting the spread of a virus that has killed millions of piglets in the United States, highlighting the risk of animal feed products as a potential transmission agent. Porcine Epidemic Diarrhea virus (PEDv) has wiped out more than 10% of the US pig population since it appeared a year ago, and has also struck in Canada, Mexico and Japan. The European Union has not been affected by this strain. In the United States, the world’s biggest pork exporter, losses from PEDv could cut pork production as much as 7% in 2014,...