In testing the Onderstepoort herd of experimental animals, totalling 224
animals, 10 positive reactors were found in 1949. Since tuberculosis was eradicated
from this herd in 1940 by slaughtering all reactors and doubtful reactors and since
with the exception of one animal, no further cases were encountered at the annual
tests during the last 9 years, this result was not only surprising, but also alarming.
Seven of the reactors were from a group of gallsickness vaccine reservoir
animals, which were kept in complete isolation in so far as other cattle were
concerned. Their bay and bedding were sterilized. The only food which was not
sterilized was the silage and the concentrate ration. Since the Onderstepoort silage
was shown to contain 4 per cent. acid, it was believed that any tubercle bacilli
which might be present, would be destroyed. The concentrate ration could carry
viable tubercle bacilli, but even if that were the case, the source of such infection
was much more likely to be human than bovine. As these animals become too
old or are for some other reason no longer suitable as donors of blood for the
vaccine, they are slaughtered and in every case a post mortem examination is
made by a veterinarian. During the last 30 years not a single case of tuberculosis
was found in this group of isolation stables. Lesions were present in six out of
the seven animals. The 7th had actinomycosis, which was thought to have been
responsible for the sensitization in this animal. An attempt was made to type
the organisms from all six animals. In four the bovine type was identified. In one
the organisms were lost and in the other, owing to difficulties in obtaining good
cultures for the biological examination, the results are not yet available.
It was concluded that a human being with open pulmonary lesions due to the
bovine type of organism must have been responsible for the infection. All the
available humans were tuberculin tested, medically examined and screened. A
number of positive tuberculin reactors were found, but no clinical cases were found,
on medical examination and on screening. Since the native personnel is constantly
changing, it was unfortunately not possible to examine all those who were in close
contact with these animals during the last two years.
In another group of three positive reactors no lesions were found and it is
considered that these animals were sensitized by infection with the human type
of organism. The native attendant in close contact with these animals was shown
to have pulmonary tuberculosis on screening, but up to now the organisms could
not be identified in his sputum by direct smear examination, nor by biological
This experience with the Onderstepoort herd, makes it abundantly clear that
man as a source of infection of the bovine with the human type of organism,
with consequent sensitization and man with open pulmonary lesions due to the
bovine type of organism, as a dangerous source of infection for bovines, can no
longer be regarded as a rare academic curiosity, but must be faced as an important
practical issue, where a serious attempt is being made to eradicate tuberculosis
from cattle and to maintain them free from sensitization. Where the bovine as
the source of infection has been eliminated and tuberculin tests are not carried
out annually, or at the most every two years, serious and disastrous setbacks may
occur, when a human being with open lesions, due to the bovine type of organism,
introduces the infection to a herd.
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