As a consequence of continued spillover of Mycobacterium bovis into cattle from wildlife reservoirs and increased globalization of cattle trade with associated transmission risks, new approaches such as vaccination and novel testing algorithms are seriously being considered by regulatory agencies for the control of bovine tuberculosis. Serologic tests offer opportunities for identification of M. bovis-infected animals not afforded by current diagnostic techniques. The present study describes assay development and field assessment of a new commercial enzyme-linked immunosorbent assay (ELISA) that detects antibody to M. bovis antigens MPB83 and MPB70 in infected cattle. Pertinent findings include the following: specific antibody responses were detected at ϳ90 to 100 days after experimental M. bovis challenge, minimal cross-reactive responses were elicited by infection/sensitization with nontuberculous Mycobacterium spp., and the apparent sensitivity and specificity of the ELISA with naturally infected cattle were 63% and 98%, respectively, with sensitivity improving as disease severity increased. The ELISA also detected infected animals missed by the routine tuberculin skin test, and antibody was detectable in bulk tank milk samples from M. bovis-infected dairy herds. A high-throughput ELISA could be adapted as a movement, border, or slaughter surveillance test, as well as a supplemental test to tuberculin skin testing.

Bovine tuberculosis of cattle results primarily from infection with Mycobacterium bovis, a member of the Mycobacterium tuberculosis complex. Despite intensive control efforts, bovine tuberculosis persists as a costly disease, with adverse impacts on animal health and welfare, the trade of animals and animal products, and the livelihoods of producers. In addition, the persistence of this disease necessitates the maintenance of costly regional and federal networks for control/eradication campaigns. The mainstays of bovine tuberculosis control are (i) abattoir surveillance with epidemiological investigations after detection of M. bovisinfected animals, to identify bovine tuberculosis-affected herds (1); (ii) application of antemortem testing for routine surveillance, movement of animals, and identification and removal of infected animals from tuberculosis-affected herds (2); and (iii) management of the disease in wildlife reservoirs, such as whitetailed deer in Michigan (3), brushtail possums (Trichosurus vulpecula) in New Zealand, Eurasian wild boar (Sus scrofa) and red deer (Cervus elaphus) in Spain (4), and Eurasian badgers (Meles meles) in the United Kingdom/Ireland (5). Tuberculin-based cellular immune assays, including measurements of in vitro interferon gamma release and measurements of delayed-type hypersensitivity (DTH) reactions via skin test procedures, are the principal diagnostic tests used for the control of bovine tuberculosis in cattle in most countries (6, 7). In the United States, the caudal fold test (CFT) (intradermal injection of M. bovis purified protein derivative [PPD] in the caudal skin fold) is used as a primary test and the comparative cervical test (CCT) (intradermal injection of Mycobacterium avium and M. bovis PPDs at separate sites in the neck) and the Bovigam assay (Prionics Ag, Schlieren, Switzerland) (an interferon gamma release assay) are used as secondary or confirmatory tests (8).Several serological tests designed to detect antibodies (Abs) to immunodominant M. bovis antigens (e.g., MPB83, MPB70, ESAT-6, and CFP10) have emerged for potential application in cattle (9-13). A commercial enzyme-linked immunosorbent assay (ELISA) for MPB83 and MPB70 (M. bovis Ab test; IDEXX Laboratories, Westbrook, ME) (9) has been approved by the Office International des Epizooties and the U.S. Department of Agriculture (USDA) for use in cattle in bovine tuberculosis control programs, although applications of this test are primarily limited to ancillary purposes such as confirmation of infections and potentially detection of M. bovis-infected cattle anergic in the skin test. A

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