Pathologic findings and association of Mycobacterium bovis infection with the bovine NRAMP1 gene in cattle from herds with naturally occurring tuberculosis

Objective-To determine necropsy and Mycobacterium bovis culture results in cattle from herds with tuberculosis, the role of the bovine NRAMP1 gene rn resistance and susceptibility to infection with M bovis, and the associatio n between magnitude of the tuberculous lesions and various types of M bovis isolates. Animals-61 cattle from herds with tuberculosis in Texas and Mexico. Procedure-61 cattle were evaluated by necropsy; 59 had positive and 2 had n egative caudal fold tuberculin intradermal lest (CFT) results. Thirty-three cattle with positive CFT results were genotyped to evaluate polymorphism o f the 3' untranslated region of the bovine NRAMP1 gene, using single-strand ed conformational analysis, 9 were resistant to M bovis with no tuberculous lesions and negative M bovis culture results, and 24 were susceptible with tuberculous lesions and positive M bovis culture results. Isolates of M bo vis were analyzed by restriction fragment length polymorphism (RFLP) on the basis of IS6110 sequences and direct-repeat fingerprinting patterns. Results-21 (35.6%; 21/59) cattle with positive CFT results had tuberculous lesions or positive culture results; in addition, 1 of 2 cattle with negati ve CFT results had tuberculous lesions and positive culture results. Tuberc ulous lesions were most common in the thorax (35/63, 55.5%) and lymphoid ti ssues of the head (10/63; 15.9%). Tuberculous lesions varied from 1 to 11/a nimal; 8 of 21 (38.1%) had solitary lesions. Associations were not found be tween resistance or susceptibility to infection with M bovis and polymorphi sm in the NRAMP1 gene or between the magnitude of the lesions and various R FLP types of M bovis isolates. Conclusions and Clinical Relevance-The NRAMP1 gene does not determine resis tance and susceptibility to infection with M bovis in cattle.