The proportional frequency of the human and bovine types of tubercle bacilli in human pulmonary tuberculosis in the middle and south of Scotland

Abstract

1. The types of tubercle bacilli have been determined in the sputum of 515 cases of pulmonary tuberculosis occurring in the middle and south of Scotland.2. Of the 515 cases 484 were human (476 eugonic and eight dysgonic) and thirty-one were bovine infections.3. With the exception of the strains from one case (case 28) all the bovine strains, seventy in number, were typical culturally and fully virulent for rabbits.4. The attenuated strains, two in number, from case 28 were slightly less virulent than typical bovine strains for rabbits and (one strain) for guinea-pigs.5. The percentage of bovine infections found in this series, including the Cumberland case, during the years 1931–9 was 6·0, but excluding that case it was 5·8.6. The percentage of bovine infections found by Munro during about the same period and covering the same regions was 5·0%.7. In Munro's series strains of bovine tubercle bacilli were obtained from fifty-eight out of 1165 persons (5·0%). Five of his cases yielded attenuated bovine strains and in one of these the pulmonary tuberculosis was preceded by tuberculosis of the thoracic spine.8. In my series the attenuated tubercle bacilli came from a case (case 28) of pulmonary tuberculosis which was preceded nearly 20 years previously by tuberculosis of the lower dorsal spine.Dr Munro and others have made post-mortem examinations on cases of phthisis pulmonalis due to bovine bacilli, but I wish to defer reference to these until we can review them altogether.In this series there are seven instances of cervical gland enlargement and one instance (case 28) of spinal tuberculosis occurring previous to the development of phthisis pulmonalis. These, I think, are examples of alimentary infection with the bovine tubercle bacillus. Thus, with the three autopsies previously mentioned, there are eleven cases, or about one-third, which are almost certainly alimentary in origin. As for the rest of the cases, 20 in number, no glandular enlargements in neck or abdomen were detected but the majority, if not all, were probably alimentary in origin, since all the persons drank a lot of raw milk and only five came into direct contact with cattle in their employment.