Bovine tuberculosis slaughter surveillance in the United States 2001-2010: assessment of its traceback investigation function.

BACKGROUND: The success of tracing cattle to the herd of origin after the detection and confirmation of bovine tuberculosis (TB) lesions in cattle at slaughter is a critical component of the national bovine TB eradication program in the United States (U.S.). The aims of this study were to 1) quantify the number of bovine TB cases identified at slaughter that were successfully traced to their herd of origin in the U.S. during 2001-2010, 2) quantify the number of successful traceback investigations that found additional TB infected animals in the herd of origin or epidemiologically linked herds, and 3) describe the forms of animal identification present on domestic bovine TB cases and their association with traceback success. RESULTS: We analyzed 2001-2010 data in which 371 granulomatous lesions were confirmed as bovine TB. From these 114 bovine TB cases, 78 adults (i.e. sexually intact bovines greater than two years of age), and 36 fed (i.e. less than or equal to two years of age) were classified as domestic cattle (U.S. originated). Of these adults and fed cases, 83% and 13% were successfully traced, respectively. Of these traceback investigations, 70% of adult cases and 50% of fed cases identified additional bovine TB infected animals in the herd of origin or an epidemiologically linked herd. We found that the presence of various forms of animal identification on domestic bovine TB cases at slaughter may facilitate successful traceback investigations; however, they do not guarantee it. CONCLUSIONS: These results provide valuable information with regard to epidemiological traceback investigations and serve as a baseline to aid U.S. officials when assessing the impact of newly implemented strategies as part of the national bovine TB eradication in the U.S.

Investigation of a Mycobacterium bovis outbreak in cattle at a Colorado dairy in 2010.

OBJECTIVE: To describe an epidemiological investigation of a bovine tuberculosis outbreak on a Colorado dairy operation. PROCEDURES: A cull dairy cow infected with Mycobacterium bovis (index cow) was detected at a Texas abattoir during routine slaughter surveillance and subsequent diagnostic testing. This initiated an epidemiological investigation that was performed in accordance with USDA regulations. RESULTS: The index cow was traced back to a Colorado dairy (index herd). Of the 908 cattle in the index herd, 101 (11.1%; 86 adult cattle > 2 years old and 15 immature cattle ≤ 2 years old) were infected with M bovis. Fourteen M bovis-infected cattle ≤ 2 years old were identified on 5 additional premises that had purchased cattle from the index herd directly or indirectly. All 115 affected cattle were infected with the same genetic type (spoligotype) of M bovis. A substantial proportion of cattle that left the index herd during the 5 years previous to the identification of the index cow were untraceable because of a lack of unique animal identification and inadequate records. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that neonatal calves can have an important role in the transmission of M bovis. Also, this report highlights the exigent need for unique individual identification of livestock, including neonatal animals, so that thorough epidemiological investigations of reportable (zoonotic or foreign animal) diseases can be conducted when necessary.

Evaluation of Serodiagnostic Assays for Mycobacterium bovis Infection in Elk, White-Tailed Deer, and Reindeer in the United States.

In 2011, the United States Department of Agriculture conducted a project in which elk (Cervus elaphus spp.), white-tailed deer (WTD) (Odocoileus virginianus), and reindeer (Rangifer tarandus) were evaluated by the single cervical tuberculin test (SCT), comparative cervical tuberculin test (CCT), and serologic tests. The rapid antibody detection tests evaluated were the CervidTB Stat-Pak (Stat-Pak), and the Dual Path Platform VetTB (DPP). Blood was collected from presumably uninfected animals prior to tuberculin injection for the SCT. A total of 1,783 animals were enrolled in the project. Of these, 1,752 (98.3%) were classified as presumably uninfected, based on originating from a captive cervid herd with no history of exposure to TB. Stat-Pak specificity estimates were 92.4% in reindeer, 96.7% in WTD, and 98.3% in elk and were not significantly different from SCT specificity estimates. Using the DPP in series on Stat-Pak antibody-positive samples improved specificity in the three species. Thirty one animals were classified as confirmed infected, based on necropsy and laboratory results, and 27/31 were antibody positive on Stat-Pak for an estimated sensitivity of 87.1%. The study findings indicate that rapid serologic tests used in series are comparable to the SCT and CCT and may have a greater ability to detect TB-infected cervids.