Comparison between a commercial and an in-house ELISA or anti-M. avium paratuberculosis antibodies detection in dairy herds in Rio de Janeiro, Brazil.

Paratuberculosis (Johne's disease) is a chronic enteritis that affects ruminants and is caused by Mycobacterium avium subsp. paratuberculosis (Map). The disease is worldwide spread and causes important economic losses. In Brazil, Map has already been isolated, but there are no enough epidemiological studies about its prevalence. In this study, 179 sera of dairy cows originated from Rio de Janeiro State, Brazil, were tested for the presence of anti-Map antibodies using two ELISAs. First one was an "in house" ELISA using a protoplasmic paratuberculosis antigen (PPA - Allied Monitor) as capture antigen and a monoclonal anti-bovine IgG conjugated to alkaline phosphatase (Sigma) and the other was "HerdChek Mpt" (IDEXX), used as standard method in this study. Fifty-nine (32.9%) samples were reactive in the PPA-ELISA. Sensitivity of ELISA-PPA in relation to HerdCheck was 47.5% and specificity was 86.8%, with 54/103 of false negatives and 10/76 of false positives. Positive predictive value of PPA-ELISA was calculated as 86% and efficiency as 64.2%. PPA-ELISA and HerdChek results were also compared by kappa test (k) and concordance index was 0.320. PPA-ELISA can be useful as a collective herd test and can be recommended as a screening test for identification of infected herds and foci of Johne's disease.