Tuberculous lesions were identified over a 2-year period in 36 clinica
lly normal red deer from a single herd. The lesions were only present
in the retropharyngeal lymph nodes and lymph nodes draining the intest
inal tract, indicating infection by the oral route. Mycobacterium aviu
m was isolated from 27 of 29 lesions examined by bacterial culture. Gr
ossly and histologically, the lesions were indistinguishable from thos
e caused by Mycobacterium bovis. DNA restriction endonuclease analysis
revealed that all the 26 M. avium isolates available for examination
had identical cleavage patterns. These patterns were identical to a Ne
w Zealand M. avium serotype 2 isolate from a pig and were very similar
to a reference strain of M. avium serotype 2. The DNA examinations in
dicated that the deer were infected from a common source that was not
identified.