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A Defined Antigen Skin Test for Diagnosis of Bovine Tuberculosis in Domestic Water Buffaloes (Bubalus bubalis).

ABSTRACT: Bovine tuberculosis (bTB) remains endemic in domestic water buffaloes (Bubalus bubalis) in India and elsewhere, with limited options for control other than testing and slaughter. The prescribed tuberculin skin tests with purified protein derivative (PPD) for diagnosis of bTB preclude the use of Bacille Calmette-Guérin (BCG)-based vaccination because of the antigenic cross-reactivity of vaccine strains with Mycobacterium bovis and related pathogenic members of the M. tuberculosis complex (MTBC). For the diagnosis of bTB in domestic water buffaloes, we here assessed a recently described defined-antigen skin test (DST) that comprises overlapping peptides representing the ESAT-6, CFP-10 and Rv3615c antigens, present in disease-causing members of the MTBC but missing in BCG strains. The performance characteristics of three doses (5, 10 or 20 μg/peptide) of the DST were assessed in natural tuberculin skin test reactor (n = 11) and non-reactor (n = 35) water buffaloes at an organized dairy farm in Hisar, India, and results were compared with the single intradermal skin test (SIT) using standard bovine tuberculin (PPD-B). The results showed a dose-dependent response of DST in natural reactor water buffaloes, although the SIT induced a significantly greater (P < 0.001) skin test response than the highest dose of DST used. However, using a cut-off of 2 mm or greater, the 5, 10, and 20 μg DST cocktail correctly classified eight, 10 and all 11 of the SIT-positive reactors, respectively, suggesting that the 20 μg DST cocktail has a diagnostic sensitivity (Se) of 1.0 (95% CI: 0.72-1.0) identical to that of the SIT. Importantly, none of the tested DST doses induced any measurable skin induration responses in the 35 SIT-negative animals, suggesting a specificity point estimate of 1.0 (95% CI: 0.9-1.0), also identical to that of the SIT and compares favorably with that of the comparative cervical test (Se = 0.85; 95% CI: 0.55-0.98). Overall, the results suggest that similar to tuberculin, the DST enables sensitive and specific diagnosis of bTB in water buffaloes. Future field trials to explore the utility of DST as a defined antigen replacement for tuberculin in routine surveillance programs and to enable BCG vaccination of water buffaloes are warranted.

SUBMITTER: Kumar T

PROVIDER: S-EPMC8418101 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundBovine tuberculosis (bTB) is a chronic disease that results from infection with any member of the Mycobacterium tuberculosis complex. Infected animals are typically diagnosed with tuberculin-based intradermal skin tests according to World Organization of Animal Health which are presently in use. However, tuberculin is not suitable for use in BCG-vaccinated animals due to a high rate of false-positive reactions. Peptide-based defined skin test (DST) antigens have been identified using antigens (ESAT-6, CFP-10 and Rv3615c) which are absent from BCG, but their performance in buffaloes remains unknown. To assess the comparative performance of DST with the tuberculin-based single intradermal test (SIT) and the single intradermal comparative cervical test (SICCT), we screened 543 female buffaloes from 49 organized dairy farms in two districts of Haryana state in India.ResultsWe found that 37 (7%), 4 (1%) and 18 (3%) buffaloes were reactors with the SIT, SICCT and DST tests, respectively. Of the 37 SIT reactors, four were positive with SICCT and 12 were positive with the DST. The results show that none of the animals tested positive with all three tests, and 6 DST positive animals were SIT negative. Together, a total of 43 animals were reactors with SIT, DST, or both, and the two assays showed moderate agreement (Cohen's Kappa 0.41; 95% Confidence Interval (CI): 0.23, 0.59). In contrast, only slight agreement (Cohen's Kappa 0.18; 95% CI: 0.02, 0.34) was observed between SIT and SICCT. Using a Bayesian latent class model, we estimated test specificities of 96.5% (95% CI, 92-99%), 99.7% (95% CI: 98-100%) and 99.0% (95% CI: 97-100%) for SIT, SICCT and DST, respectively, but considerably lower sensitivities of 58% (95% CI: 35-87%), 9% (95% CI: 3-21%), and 34% (95% CI: 18-55%) albeit with broad and overlapping credible intervals.ConclusionTaken together, our investigation suggests that DST has a test specificity comparable with SICCT, and sensitivity intermediate between SIT and SICCT for the identification of buffaloes suspected of tuberculosis. Our study highlights an urgent need for future well-powered trials with detailed necropsy, with immunological and microbiological profiling of reactor and non-reactor animals to better define the underlying factors for the large observed discrepancies in assay performance, particularly between SIT and SICCT.

Project description:Traumatic pericarditis (TP) remains a serious problem facing bovine producers; particularly in the developing countries; causing severe economic losses. This study was carried out on 47 buffaloes including; control buffaloes (n = 20) and buffaloes with TP (n = 27) at Assiut governorate, Egypt. All animals were subjected to thorough clinical examination, whole blood profiling, blood serum biochemical assays, and radiographic and ultrasonographic examinations. The recorded ultrasonographic findings included; the contractility, contour and shape of the reticulum, shape and size of the heart and spleen involvement. All data were statistically analysed. Buffaloes with TP showed lymphocytic leucocytosis, increase in serum activities of AST, hyperproteinaemia, hypoalbuminaemia and hyperglobulinaemia. Radio-opaque metal foreign bodies, cardiomegaly and loss of the normal cardiac shape and contour were the most common radiographic findings in the diseased buffaloes. Ultrasonographically, the diseased buffaloes showed either acute pericarditis (n = 10) or chronic suppurative pericarditis (n = 17). Complete cessation of reticular contractions (0/3 min) and displacement of the reticulum from the diaphragm by a distance about 2.6-4.5 cm were the most common ultrasonographic findings of both types of pericarditis. In addition, the reticulum had uneven contour and the heart showed characteristic changes in its size, shape and contractility that was either accelerated or reduced. Reticular abscesses and peritoneal effusions were also imaged in all diseased buffaloes. In acute TP; the affected heart was enlarged with strong and clear cardiac contractions. Accumulation of hypoechoic fluids interspersed with echogenic deposits of fibrin within heart tissue and pericardium was observed. In chronic suppurative pericarditis, cardiomegaly, thickening of the cardiac wall and loss of the characteristic recognisable heart shape were the common ultrasonographic findings. Accumulation of hypoechoic fluids (usually pus) interspersing with echogenic deposits of fibrin within the pericardium, ventricles, atria and valves was also observed. In conclusion, ultrasonography with the aids of other diagnostic tools such as clinical findings, laboratory analysis and radiography has a high efficacy in evaluation of diseased buffaloes with TP.

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A Defined Antigen Skin Test for Diagnosis of Bovine Tuberculosis in Domestic Water Buffaloes (Bubalus bubalis).

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