Tuberculous lesions in free-ranging white-tailed deer in Michigan.

Descriptions of the anatomical distribution of Mycobacterium bovis gross lesions in large samples of white-tailed deer (Odocoileus virginianus) are lacking in the scientific literature. This report describes the distribution of gross lesions in the 58 white-tailed deer that cultured positive for M. bovis among the 19,500 submitted for tuberculosis testing in Michigan (USA) in 1999. For the vast majority (19,348) of those tested, only the head was submitted; for others, only extracranial tissues (33) or both the head and extracranial tissues (119) were available. Among those deer that cultured positive, cranial gross lesions were noted most frequently in the medial retropharyngeal lymph nodes, although solitary, unilateral parotid lymph node lesions also were found. Extracranial lesions occurred most commonly in the thorax. The distribution of lesions largely agreed with the few existing case reports of the M. bovis in white-tailed deer, although gross lesions were also found in sites apparently not previously reported in this species (liver, spleen, rumen, mammary gland). Some practical issues that may assist future surveillance and public education efforts are also discussed.