title: Prevalence of Bovine Tuberculosis in Egyptian Cattle and the Standardization of the Interferon-gamma Assay as an Ancillary Test.
abstract: Bovine tuberculosis (bTB) caused primarily by Mycobacterium bovis continues to cause significant losses in the cattle industry and is a major public health problem. Despite its worldwide application, the IFN-γ assay has not been applied in Egypt. The aim of this study was to determine the appropriate cut-off value of IFN-γ assay to complement the skin test screening in Egypt. The relative sensitivity (Ser ) of PPD and antigen cocktail-based IFN-γ assays (IFN-γ-BA and IFN-γ-EC) was analysed retrospectively, relative to bTB confirmatory tests (culture and PCR), using single cervical tuberculin (SCT) test reactors during 2011-2013. The absolute specificity (Sp) was studied using blood samples collected from cattle from one bTB-free herd. Analysis of the bTB database-generated sheets indicates the infection rate had decreased from 2009 to 2012 and then increased in 2013. The disease is concentrated in the Egyptian Nile Delta and Valley relative to elsewhere in the country. The cut-offs for IFN-γ-EC assay could be optimized to provide higher sensitivity, comparable to cut-offs for IFN-γ-BA assay. Data analysis suggests (PPDbOD  > 0.1, PPDbOD  - NILOD  > 0.05 and PPDbOD  > PPDaOD ) and (ECOD  - NILOD  ≥ 0.1) cut-off strategies to get optimal IFN-γ-BA and IFN-γ-EC assays results respectively. To our knowledge, this is the first report describing the prevalence of bTB in cattle in Egypt and pointing out the appropriate cut-off criteria to optimize IFN-γ assay as a routine ancillary test for diagnosis of bTB in Egypt.
authors.affiliation: Department of Microbiology, Faculty of Veterinary Medicine, Alexandria University, Edfina, Rosetta-line, Egypt.
authors.forename: G S
authors.initials: GS
authors.lastname: Abdellrazeq
authors.affiliation: Department of Microbiology, Faculty of Veterinary Medicine, Alexandria University, Edfina, Rosetta-line, Egypt.
authors.forename: M M
authors.initials: MM
authors.lastname: Elnaggar
authors.affiliation: Central Department of Public Health and Abattoirs, General Organization for Veterinary Services, Cairo, Egypt.
authors.forename: H S
authors.initials: HS
authors.lastname: Osman
authors.affiliation: Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Pullman, WA, USA.
authors.forename: W C
authors.initials: WC
authors.lastname: Davis
authors.affiliation: LIONEX Diagnostics and Therapeutics, Braunschweig, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Singh
mesh_terms: D000818:Animals; D002417:Cattle; D004534:Egypt / Q000453:epidemiology; D007371:Interferon-gamma / Q000097:blood*; D009163:Mycobacterium bovis / Q000276:immunology*; D015995:Prevalence; D014374:Tuberculin Test / Q000662:veterinary; D014380:Tuberculosis, Bovine / Q000175:diagnosis / Q000453:epidemiology*
chemical_list: D007371:Interferon-gamma
keywords: IFN-γ assay; bovine tuberculosis; cut-off values; tuberculin skin test