ABSTRACT
Mycohacterium avium subspecies of Paratuberculosis is the cause of paratuberculosis or Johne's disease. Paratuherculosis is a chronic and progressive infectious enteric disease that affects domestic and wild animals, mostly ruminants. This study was carried out for detection of subclinical forms of Johne's disease using direct PCR and cultivation methods. A total 119 fecal samples were collected Holstein-Friesian cattle herds in Razavi khorasan province of Iran. Among these, 16 samples were taken from cows with advanced clinical signs of Johne's disease. 101 were taken from cows without clinical signs. The fecal samples were tested for presence of Mycobacterium paratuberculosis by directed Nested-PCR and culture on Herrold s media with and without Mycobactin J. The samples of cows with clinical signs, 14[87.5%] and 13[81.3%] were positive by PCR and cultivation assays, respectively. These numberes for the 101 cows without clonical signs of Johne's disease were 10[9.7%] and 12[11.7%]. In conclusion, according to the current report of bacterial detection from different places and the economic importance of John's disease, it is logical and essential that the prevalence rate of the disease in dairy cattle is initially determined by at least two different types of samples and tests and afterwards the control programs are adopted