In a study population comprising young adults from Denmark it was found that the tuberculosis morbidity was much lower among persons infected from bovine than from human sources. In an attempt to reveal the possible cause of this difference an analysis was made of the frequency of pulmonary calcifications in these two groups. The results of this study show that the frequency of calcifications is small, probably negligible, in the bovine-infected group as compared with that in the group infected from human sources. This observation suggests that the difference between the infections from bovine and human sources may lie in the dose-virulence of the infecting agent or in the route of infection.

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PubMed1967

Epidemiological basis of tuberculosis eradication. 6. Tuberculin sensitivity after human and bovine infection.

The morbidity from pulmonary tuberculosis and the frequency of pulmonary calcifications have been found to be very much lower among persons infected from bovine sources than among persons infected from human sources. This difference might be wholly or partly due to an attenuated virulence of the infecting bovine tubercle bacilli; the purpose of the study reported was to examine this question. The problem was attacked indirectly by means of a comparison between the tuberculin sensitivity among human-source and bovine-source reactors. The study shows that the sensitivity is stronger among the bovine-source reactors, thus affording no support for the hypothesis that bovine infection may be of low virulence. The alimentary route of infection therefore probably accounts for the low frequency of pulmonary calcifications and possibly also for the low morbidity among the reactors infected from bovine sources.It would be of great significance for tuberculosis control programmes if it were possible to distinguish the low-risk group of bovine-source reactors from the high-risk group of human-source reactors. However, although the former have larger tuberculin reactions, the difference is still so small (of the order of a few millimetres) that the tuberculin reaction cannot be used in practice to differentiate the two groups.

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PubMed1966

Epidemiological basis of tuberculosis eradication. 3. Risk of pulmonary tuberculosis after human and bovine infection.

Cattle tuberculosis was eradicated in Denmark more than 10 years ago, but still a sizable proportion of Danish tuberculin reactors owe their sensitivity to tuberculous infection derived from bovine sources. This paper deals with the question whether the risk of pulmonary tuberculosis after such infection is different from that after tuberculous infection acquired from man. This problem has been studied by utilizing data from the Danish tuberculosis mass campaign, 1950-52, including eight years of follow-up, and data from the eradication programme for cattle tuberculosis. It is shown that the tuberculin reactors can be divided into two groups carrying a widely different risk of late pulmonary tuberculosis: one, infected from bovine sources, carrying a low risk; the other, infected from human sources, carrying a relatively high risk.

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