190
Bovine Tuberculosis
Experiment No. 5
ANKOLE CALF NO. 3588
Received 50 mg. T.B. strain B.V. 34 seven-day-
old culture on serum subcutaneously on March 14,
1939. Killed in extremis April 4, 1939. Duration
of infection 21 days.
Post-mortem. Calf very emaciated. Right
prescapular (regional lymph) gland enlarged and
indurated and lying in a mass of fibro-caseous
material. Mediastinal gland enlarged and in-
durated. Other glands enlarged and indurated.
Lungs distended and full of miliary tubercles.
Liver—numerous miliary tubercles. Kidneys—
miliary tuberculosis. Spleen—miliary tuberculo-
sis. This calf showed no resistance to infection
and died of acute miliary tuberculosis.
ANKOLE CALF NO. 3585
Received 50 mg. seven-day-old culture of
strain B.V. 34 on serum, subcutaneously on
March 14, 1939. Died after 59 days.
Post-mortem. Emaciated. Both lungs distend-
ed and full of tubercles about 3 mm. in dia-
meter. Marked hæmorrhagic reaction around
the tubercles. Spleen swollen and on section
showed numerous tubercles. Prescapular, pres-
ternal, mediastinal, mesenteric, and hepatic glands
all tuberculous. Liver—dark in colour, swollen
and covered with numerous tubercles ranging
in size from a millet seed up to a diameter of 3-4
mm. These extended throughout the organ.
Controls. (1) Rabbit No. 1177 : Inoculated
intravenously with 0.001 mg. of same culture.
Died after 41 days. Post-mortem: Severe
generalized miliary tuberculosis.
(2) Rabbit No. 1178: Inooulated subcuta-
neously with 10 mg. of same culture. Died after
117 days. Post-mortem: Severe generalized
tuberculosis.
Experiment No. 6
ANKOLE CALF NO. 3583
Inoculated with 50 mg. of strain B.V. 34 on
March 15, 1939. Weight :
252 lb. Died
August 16, 1939. Weight : 250 lb. Duration
of infection : 154 days.
Post-mortem. Condition poor. Lungs show
numerous miliary tubercles. Liver showed miliary
tubercles. Regional gland enlarged and full of
caseous material. Glands generally enlarged and
indurated.
ZEBU CALF NO. 3582
Inoculated with 50 mg. of strain B.V. 34 on
March 15, 1939. Died on October 25, 1939.
Duration of infection: 194 days.
Post-mortem. Calf in poor condition. The
only sign of tuberculosis was a number of small
millet seed tubercles in the spleen and an abscess
in the regional gland. Lungs and liver—normal
This calf was suffering from a severe gastro
enteritis which was the probable cause of death.
Control. Goat No. 1171: Inoculated sub-
cutaneously with 10 mg. of the same culture.
Died after 41 days of acute miliary tuberculosis.
Discussion
The effect of the tubercle bacillus on the
tissues depends on the virulence of the particular
strain used and on the resistance of the host.
Thus the reaction will differ with similar hosts
inoculated with different strains and the same
standard strain may provoke different reactions
in hosts of the same species. Further, it has
been observed that the reaction of a susceptible
host to a strain of low virulence is similar to that
of a resistant host to a fully virulent organism.
In these experiments the strain of tubercle
bacillus was of a standard virulence and the
object was to determine the degree of resistance
of the hosts concerned—Zebu cattle—in view of
the observations in Uganda which were recorded
in Part I of this paper.
It is generally accepted that a bovine strain
of standard virulence will kill an average calf
of the European breeds in about 10 weeks when
inoculated subcutaneously in a dose of 50 mg.
[A. S. Griffith, 1930].
From the results obtained it will be seen that
of the eight Zebu calves inoculated all showed
a marked degree of resistance, whilst the three
Ankole calves showed little resistance and reacted
in a similar manner to European breeds. It
would seem that in the resistant Zebu calves
there was a marked generalized infection which
was gradually overcome to a greater or lesser
extent, depending on the degree of individual
resistance, but in all cases there was sufficient
resistance to preserve health, whilst in some an
almost completely successful reaction had taken
place.
Thus calves killed at 90 days after inoculation
showed macroscopic evidence of a fairly severe
infection whilst those which were allowed to
survive for longer periods up to 354 days improved
markedly on the earlier ones and demonstrated
a progressively successful and almost complete
resistance to a lethal dose of a virulent strain of
tubercle bacilli.
The sections examined, although few in
number, demonstrate the general histo-patho-
logical process of recovery. Thus in the calves
allowed to survive 90 days there was evidence of
marked tissue reaction going on in the lungs
whilst the lungs of an animal infected for 354
days were quiescent and merely showed a few
scars to indicate the battle which it has success-
fully survived.