Mycobacterium avium subsp. paratuberculosis (Map) is the etiologic agent of a severe gastroenteritis in ruminants. We observed injuries compatible with paratuberculosis in mouflon. Morphology, histopathology, isolation, biochemical typification of strains and the study by molecular biology, are described for the first time in Argentina. The objective was to determine the presence of Map from wildlife species which may open up the possibility of wildlife to domestic ruminant transmission.The samples came from one animal of the province of Buenos Aires, Argentina. Haematoxylin-and-eosin-stained sections of the gross intestine showed hyperplasia in corion and submucosa with diffuse infiltration of epithelioid cells.For bacteriological isolation the fecal specimen was decontaminated by hexadecylpyridium chloride (HPC) technique and cultured on Herrold's egg yolk medium (HEYM), with and without mycobactin, and in Mycobacterial Growth Indicator Tube (MGIT) with mycobactin.The identification and molecular typing studies were performed at the Institute of Biotechnology-INTA, Castelar, Argentina.A loopfull of bacteria from the culture was taken to perform the PCR. They were resuspended in 100 μl of distilled water and then boiled during 30 min. 10 μl.of the supernadant were used to perform the PCR.The specific insertion sequence IS900 of Map was used like target. The PCR was carried out producing a DNA fragment of 217 bp.Primary colonies of Map appeared from 4 weeks after inoculation in HEYM with mycobactin and fluorescence in MGIT medium.The isolates were stained by Ziehl-Neelsen's method and examined microscopically for acid-fast organisms that have the morphological characteristics of Map. The strain was positive to IS900.Paratuberculosis has been also diagnosed in farmer-deer, alpacas, elk, white tailed deer, mule deer, bighorn sheep, Rocky Mountain goats and bison.Wildlife would appear to the potential reservoirs to Map and this has implications for the control to Paratuberculosis in domestic animals and possible human health.