title: Extent of Mycobacterium bovis infection in dairy cattle herds subject to partial culling as determined by an interferon-gamma assay.
abstract: The interferon-gamma (IFN-γ) assay is employed as a complementary diagnostic test for bovine tuberculosis (BTB) in many countries. To simplify this assay, we established a 96-well plate format using the ESAT-6 and CFP-10 antigens and then employed it to determine the extent of Mycobacterium (M.) bovis infection in dairy herds with a history of BTB outbreaks in a country where only selective culling is practiced. The sensitivity and specificity of this IFN-γ assay were 85.9% and 100%, respectively, based on comparison with the conventional single intradermal tuberculin test (SIDT). The IFN-γ assay was also positive in 30.4% and 36.8% of SIDT-negative animals from herds with recent and remote BTB outbreaks, respectively. Of 14 SIDT-negative, IFN-γ positive cattle, five (35.7%) were culture positive and an additional six were positive based on a polymerase chain reaction-based test for M. bovis. Therefore, the IFN-γ assay has the potential to serve as a specific and sensitive test for M. bovis infection in dairy cattle. Further, the results indicated that a substantial portion of SIDT-negative animals in herds with previous BTB outbreaks were actually infected with M. bovis. Accordingly, the present selective-culling strategy may require modifications to include this more sensitive assay.
authors.affiliation: Department of Microbiology and Institute for Immunology and Immunological Diseases, Brain Korea 21 Plus Project for the Medical Sciences, Yonsei University College of Medicine, Seoul 120-752, Korea.
authors.forename: Sungmo
authors.initials: S
authors.lastname: Je
authors.forename: Un-Chang
authors.initials: UC
authors.lastname: Yeo
authors.forename: Taeksun
authors.initials: T
authors.lastname: Song
authors.forename: Ki-Cheol
authors.initials: KC
authors.lastname: Kim
authors.forename: Sung-Yun
authors.initials: SY
authors.lastname: Park
authors.forename: Man-Jung Isabel
authors.initials: MJ
authors.lastname: Kim
authors.forename: Sang-Nae
authors.initials: SN
authors.lastname: Cho
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D002417:Cattle; D005260:Female; D059425:Interferon-gamma Release Tests / Q000662:veterinary*; D009163:Mycobacterium bovis / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D056910:Republic of Korea / Q000453:epidemiology; D014380:Tuberculosis, Bovine / Q000175:diagnosis* / Q000453:epidemiology* / Q000382:microbiology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C553218:CFP-10 protein, Mycobacterium bovis
keywords: IFN-gamma assay; Mycobacterium bovis; bovine tuberculosis