Dairy cows that are no longer productive are routinely slaughtered for ground beef. The Crohn's connection is a delicate one for dairy producers. They cannot afford to ignore it, but neither do they want to scare the public, Garry said. The producers are very edgy about the whole thing. Johne's was first identified more than a century ago, but many farmers paid it little heed.
Cattle can carry the infection for years before showing symptoms.
An Agriculture Department study in 1996 found that 22 percent of U.S. herds had at least 10 percent of their cattle infected with Johne's. Kevin Condon, a dairy farmer near Oshkosh, Wis., said the disease was found in his herd more than 10 years ago. He has kept it under control by testing his cattle when he can afford it, taking precautions with calves and being more careful in handling of manure and feed. Sick cattle are sent to slaughter. Everyone would like to eliminate it altogether, but it's difficult.