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Comparative evaluation of different diagnostic techniques for detection of naturally occurring paratuberculosis in Gaddi goats

Thakur, Monika, Maity, Madhulina, Sharma, Shweta, Gupta, Vipan Kumar
Small ruminant research 2019 v.174 pp. 92-98
Bacilli, chi-square distribution, diagnostic techniques, enzyme-linked immunosorbent assay, goats, histopathology, ileum, lymph nodes, paratuberculosis, polymerase chain reaction, staining, tissues
The present study was aimed to evaluate the diagnostic efficacy of different techniques for detection of naturally occurring caprine paratuberculosis, considering histopathology as a parameter of infection. A total of 68 Gaddi goats slaughtered during September 2013 to March 2014 were investigated. Samples were screened for paratuberculosis by gross, histopathology, Ziehl-Nielsen (ZN) staining of impression smear and tissues sections (terminal ileum, ileo-caecal lymph node and mesenteric lymph node), ELISA, AGID and paraffin embedded tissue PCR. On gross, histopathology, ZN staining of impression smear as well as tissue sections from 68 goats revealed typical lesions, acid-fast bacilli and granulomatous inflammatory changes suggestive of paratuberculosis in 46.15% (18/39), 57.35% (39/68), 43.58% (17/39) and 35.89% (14/39) respectively. The sensitivity of ELISA, AGID and IS900/IS1311 paraffin tissue PCR was 74.35% (29/39), 61.53% (24/39) and 43.58% (17/39) respectively. All tests viz. histopathology, ZN staining, ELISA, AGID and paraffin embedded tissue PCR showed relatively higher sensitivity in animals with grade III and IV lesions when compared to grade I and II. Agreement among different tests was statistically analyzed by kappa statistics and chi-square test. The findings of the present study indicate that ELISA was most sensitive amongst the serological assays and histopathology was most sensitive of the post-mortem tests. However, combination of one of the serological tests along with histopathology and paraffin tissue PCR was found to be a better indicator for making confirmatory diagnosis of paratuberculosis in Gaddi goats.