Comparison of ELISA method, PCR and Ziehl-Neelsen staining of the rectal mucosa for detection of Mycobacterium avium subsp. paratuberculosis infection in cattle

Mycobacterium avium subsp. paratuberculosis is the etiologic agent of Johne’s disease in cattle and other ruminants. This disease is considered the most extensive, in terms of incidence, and the most important disease, in terms of economic importance, in the animal husbandry industry. Rapid and accurate diagnosis of disease is extremely important in preventing the spread of disease in the herd. In the present study, the prevalence of Mycobacterium avium subsp. paratuberculosis infection in slaughtered cows in Ahvaz slaughterhouse was evaluated and compared using three methods, rectal scraping PCR, acid-fast staining and serum ELISA. In this study, blood and rectal scraping samples were collected from 200 cows. Serum ELISA was performed with a commercial ELISA kit, Ziehl-Neelsen staining was done based on conventional method, and PCR was performed using IS900 and hspX specific primers for Mycobacterium avium subsp. paratuberculosis. Rectal scraping PCR detected 27 of 200 cows (13.5%) infected with Mycobacterium avium subsp. paratuberculosis, acid-fast staining of the rectal mucosa detected 8 cows (4%), and serum ELISA detected only 6 cows (3%). Comparing the results of these three tests shows moderate agreement between acid-fast staining and rectal scraping PCR tests (kappa score, 0.42), low agreement between ELISA vs. rectal scraping PCR (kappa score, 0.08), and ELISA vs. acid-fast staining (kappa score, 0.11). According to the results of the present study, although the rectal scraping PCR showed better results in rapid diagnosis of the infected cows, but in order to achieve a more precise result for rapid diagnosis of the infected cows and also in epidemiological studies for determining the prevalence of Mycobacterium avium subsp. paratuberculosis infection, simultaneous conduct of rectal scraping PCR and serum ELISA can be recommended.