title: Evaluation of the single cervical skin test and interferon gamma responses to detect Mycobacterium bovis infected cattle in a herd co-infected with Mycobacterium avium subsp. paratuberculosis.
abstract: This study reports the performance of the single intradermal tuberculin (SIT) test and the interferon-gamma (IFN-γ) assay for Mycobacterium bovis in a cattle herd with high prevalence of paratuberculosis (PTB). A total of 58/350 animals were selected for necropsy based on one or more of the following criteria: positive to SIT, IFN-γ, a breeding cow that seroconverted to PTB and showed signs compatible with a wasting disease. Infection status was determined by post mortem diagnostic tests that included histopathology examination, mycobacterial cultures and PCR identification for M. bovis and Mycobacterium avium subsp. paratuberculosis (MAP). In 7/58 animals primary tuberculosis (TB) lesions, affecting only the retropharyngeal and/or mediastinal lymph nodes, were found; 3/7 animals were found SIT positive. PTB was confirmed in 35/58 animals, of which 30 had seroconverted and 14 had typical clinical signs. 45/58 animals were IFN-γ(+) using the most stringent criterion (cut-off point ≥ 0.05); however, IFN-γ test was only positive in 33 animals when using a higher threshold (cut-off point ≥ 0.1). Three animals co-infected also showed extensive TB and diffuse PTB lesions. These results show that the combined use of SIT and IFN-γ, as interpreted using official guidelines, detected all confirmed cases of TB. Individually, the sensitivity of the SIT was inadequate to diagnose TB-positive animals with an advanced stage of PTB. The large number of IFN-γ(+) animals with no visible TB lesion could be due, in part, to some protection conferred by prior infection with MAP.
authors.affiliation: Departamento de Anatomía y Anatomía Patológica Comparadas, Universidad de Murcia, 30100 Murcia, Spain. Electronic address: jseva@um.es.
authors.forename: Juan
authors.initials: J
authors.lastname: Seva
authors.affiliation: Departamento de Anatomía y Anatomía Patológica Comparadas, Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Sanes
authors.affiliation: Departamento de Producción Animal, Facultad de Veterinaria. Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Ramis
authors.affiliation: Departamento de Anatomía y Anatomía Patológica Comparadas, Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Mas
authors.affiliation: Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas (CNB-CSIC) , 28049 Madrid, Spain.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Quereda
authors.affiliation: TB Research Group, Veterinary Laboratories Agency, Addlestone, Surrey, UK.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Villarreal-Ramos
authors.affiliation: School of Veterinary Medicine, University of Antioquia, Medellin, Colombia.
authors.forename: David
authors.initials: D
authors.lastname: Villar
authors.affiliation: Departamento de Anatomía y Anatomía Patológica Comparadas, Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Pallares
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology* / Q000473:pathology; D060085:Coinfection; D005260:Female; D007371:Interferon-gamma / Q000276:immunology; D016927:Mycobacterium avium subsp. paratuberculosis / Q000502:physiology; D009163:Mycobacterium bovis / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D010283:Paratuberculosis / Q000150:complications* / Q000276:immunology / Q000473:pathology; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000276:immunology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013030:Spain; D014373:Tuberculin / Q000276:immunology; D014374:Tuberculin Test / Q000592:standards / Q000662:veterinary*; D014380:Tuberculosis, Bovine / Q000150:complications* / Q000175:diagnosis* / Q000473:pathology
chemical_list: D011994:Recombinant Proteins; D014373:Tuberculin; D007371:Interferon-gamma
keywords: Cattle; IFN-γ; Mycobacterium avium subsp. paratuberculosis; Mycobacterium bovis; Paratuberculosis; Single cervical skin test; Tuberculosis