A comparison of ELISA and histopathology for the detection of paratuberculosis in dairy cattle

Johnes disease or paratuberculosis is an infectious disease caused by Mycobacterium paratuberculosis and has been described in numerous ruminate species. In cattle, intractable diarrhea, emaciation, and hypoproteinemia in animals older than 19 months characterize the disease. The objectives of this study were to determine the association between severity of histological enteric lesions and the serum absorbed enzyme-linked immunosorbent assay (ELISA) antibody test and comparative efficacy of absorbed ELISA antibody test with histopathological finding of naturally acquired paratuberculosis in the infected dairy cattle of Iran. Fifty mature dairy cows, culled from four M. paratuberculosis-infected herds in Iran were enrolled in this study. Poor physical condition was the major criteria for selection of the cows. Prior to slaughter, blood samples were collected from jugular vein from each animal. All cattle were inspected after slaughter. and samples from 50 cases that showed thickening of different parts of the intestine and enlargement of mesenteric lymph nodes were obtained for histopathological examination. At microscopic examination, specific histopathological characteristics of paratuberculosis were observed in 19 cases. Tuberculoid reactions were observed in five cases, and lepromatous reactions were observed in 14 cases out of the total. Of the total, 19 samples had histopathological finding of paratubercolosis, and only eight animals exhibited a positive antibody response when subjected to an ELISA assessment. The sensitivity, specificity, positive predictive value, and negative predictive value for absorbed ELISA was 42.1%, 100%, 100%, and 73.8%, respectively.