Figure 1

Distribution by age of successful traceback investigations to a herd of origin in the U.S. and number that yielded at least one affected herd, 2001–2010. Of the 334 fed bovine TB cases identified at slaughter between 2001–2010, the majority (256, 77%) were classified as imported animals (254 from Mexico and 2 from Canada). Traceback to a herd of origin for these animals was beyond the scope of this study. Seventy-eight (23%) were determined to be domestic, potentially having a herd of origin in the U.S. From these domestic fed bovine TB cases, 10 (13%) were successfully traced to a herd of origin in the U.S. and 68 (87%) cases were not. As part of the traceback investigations on the 10 domestic fed bovine TB cases identified at slaughter that were successfully traced to a herd of origin in the U.S., in 5 of them additional infected animals (affected herds) were identified when either the herd of origin or an epidemiologically linked herd (identified through secondary trace-in or trace-out investigations) were tested using the official bovine TB program tests. Of the 37 adult bovine TB cases identified at slaughter between 2001–2010, 1 was determined to be imported (from Canada) and 36 (97%) domestic. From these domestic adult bovine TB cases, 30 (83%) were successfully traced to a herd of origin in the U.S. and 6 (17%) were not. As part of the traceback investigations on the 30 domestic adult bovine TB cases identified at slaughter that were successfully traced to a herd of origin in the U.S., in 21 (70%) of these additional infected animals (affected herds) were identified when either the herd of origin or an epidemiologically linked herd (identified through secondary trace-in or trace-out investigations) were tested using the official bovine TB program tests.