The diagnostic possibilities of bovine paratuberculosis using skin test with avian PPD

ALVARADO PINEDO, F.; MOYANO R. D.; PERALTA L.; DI PAOLO, L. A.; ROMERO MA; ROMANO, M.; TRAVERIA G.

Nantes

Congreso; 13th International Colloquium on Paratuberculosis; 2006

l'International Association for Paratuberculosis

Paratuberculosis an ileocolitis mostly present in ruminants is caused by Mycobacterium avium subsp paratuberculosis the clinical manifestations includes diarrhea, progressive weight loss, general wasting and decreased milk production.Cell-mediated immune response predominates earlier in the first stages of the disease, to achieve an early antemortem detection under field condition the skin test is one choice. The aim of this work was to set up some performance characteristics of skin test with avian tuberculin. No significant differences were found, with receiver operating characteristic curve (ROC) (P= 0,14) between cervical tuberculin skin test (CTST) and caudal fold tuberculin skin test (CFTST), although CTST detected more reactants. Bayesian approach found differences (P= 0,0031) between the means of two different concentrations of avian PPD (0,5 mg/mL vs. 2 mg/mL), showing higher skin fold differences with 2 mg/mL, however with ROC no differences were evident (P= 0,931) between both concentration AUC= 0,718 (0,5 mg/mL) and AUC= 0,719 (2 mg/mL). The ROC test estimate a sensitivity of 69% and a specificity of 86,2% and cut off > 0 mm. Bayesian inference calculate 42,5% for positive predictive value (PPV), 91,6% negative predictive value (NPV), 3,3 for positive likelihood ratio (LR+) and 0,4 negative likelihood ratio (LR-). Also, we apply the ROCRegression package to know the effect of covariates on the skin test, according to results, the performance of the test is improved if 3 to 5 rounds of serial skin tests is applied between an elapsed time not superior to 3 months in order to detect the higher number of subclinical diseased animals.