Investigation on the occurrence and pathology of paratuberculosis (Johne’s disease) in apparently healthy cattle in Jordan

Paratuberculosis (Johne’s disease) is an infectious, incurable, chronically progressive granulomatous enteritis which affects domestic and exotic ruminants. The causative agent is Mycobacterium avium paratuberculosis (Mycobacterium johnei), a slow growing mycobactin-dependent acid-fast bacillus. We investigated the occurrence of Johne’s disease in apparently healthy cattle, using 263 ileum and corresponding mesenteric lymph nodes, by histopathological examination, and 170 ileum and 120 mesenteric lymph nodes by immunohistochemical examination. The occurrence of the disease was 65% and 66% using immunohistochemistry and histopathology techniques, respectively. When Ziehl-Neelsen (ZN) and ELISA techniques were implemented, the occurrence was 1% (4/120) and 3% (8/278), respectively. Grading from I–IV of histopathological lesions based on type of cellular infiltrate and severity of lesions revealed that most of the positive cases were in grade I and II. Furthermore, staging I–III of immunohistochemistry results, has presented a high number of positive cases in stage I. ZN stain showed a very low occurrence; however, it is still used as a confirmatory test for clinical cases. On the other hand, ELISA technique showed a low occurrence of the disease (3%) in this study reflecting the low sensitivity of the technique in diagnosis of subclinical Johne’s disease (JD). These results showed that histopathology is a very good diagnostic method for subclinical paratuberculosis in cattle. From the present study, we conclude that the occurrence of JD in cattle is high in Jordan. It is interesting to note that this is the first study of JD in cattle in Jordan, and the results strongly suggest alarming fears of severity of the disease at the national level. The urgent need for national control strategies are well founded due to the economical importance of the disease.