Merck and Company is closing eight manufacturing plants and eight research sites, mostly in foreign countries. The company says it is part of an ongoing consolidation following the merger with Schering-Plough Last November. The merger made Merck the world’s second-largest drug maker. The company has said it plans to eliminate about 15 percent of the combined workforce, at a savings of about $3.5 billion a year, starting in 2012. The two campuses in Upper Gwynedd, which employ a combined total of about 10,000, are not affected by the cutbacks.