Detection of Mycobacterium avium subsp. paratuberculosis in kidney samples of red deer (Cervus elaphus) in Portugal: Evaluation of different methods.

Paratuberculosis or Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (Map), is a chronic granulomatous enteritis affecting both domestic and wild ruminants. The present work is part of a wider set of studies designed to assess the prevalence of paratuberculosis in free ranging red deer (Cervus elaphus). With that purpose, 877 free-ranging red deer legally hunted in the Centre-eastern Portugal were submitted to necropsy and sampled for molecular methods, microbiology and histopathology. Thirty-seven (4.2%) kidneys revealed acid-fast bacilli when screened with the Ziehl-Neelsen technique. Map was detected by IS900 polymerase chain reaction (PCR) in thirty (81.1%) of the Ziehl-Neelsen positive kidneys. Subsequent PCR and/or culture from the different organs of the 37 examined animals allowed us to detect 86.4% (32 animals) infected red deer. Our results suggest that renal involvement in Map infected deer may be underdiagnosed and thus the routine examination of this organ and its inclusion in PCR techniques designed for Map detection could substantially improve the diagnostic of paratuberculosis in red deer.