Bacteriology of Skin Lesions of Tuberculin Reacting Cattle

Abstract

This is a preliminary report on the bacteriology of 189 cases of so-called skin tuberculosis of cattle.

In recent years, as the tuberculosis eradication program is succeeding in reducing the number of typical cases of bovine tuberculosis in cattle, there is a marked relative increase in the number of so-called skin lesions and no-lesion-reactors. In Utah, this has resulted in a large majority of the cattle, which react to the tuberculin test, and which on post-mortem examination, fail to show any lesions, or lesions which are confined to the skin or to the subcutaneous tissue.

More than 90% of the lesions studied in this series came from animals which had given a positive tuberculin reaction. The remainder had not been tested because they were obtained in routine examination of regular abattoir material.

Only one of the 189 skin lesions yielded a typical Mycobacterium tuberculosis (bovine type) and this came from an animal which appeared to have generalized bovine tuberculosis. This suggests the occurrence of true bovine tuberculosis skin lesions, but it also indicates the probability that the rather rare positive animal inoculation tests of Day, 1 Watson, 2 Mitchell, 3 and others might have been from similar unusual cases.

Careful search of these skin lesions from tuberculin-reacting cattle revealed the presence, in all of them, of acid-fast rods, as well as one or more forms of acid-fast or non-acid-fast coccoid, diphtheroid, or streptococcoid organisms, or branching filaments. These are all probably different stages or forms of a pleomorphic organism.

All but one of the 189 skin lesions, as well as organs from several no lesion-reactors yielded in culture one or more forms of markedly pleomorphic, facultative acid-fast, Gram positive organisms. Of these, a few strains-the only ones tried up to the present—produce fairly constant results when inoculated into male or pregnant female guinea pigs.