146
Contagious Abortion of Cattle, Sheep and Goats
[VOL. XVIII, PART III
Antigenic sensitivity
The majority of the present collection of Indian strains have been tested for differences in antigenic
sensitivity, and within the limits of ordinary error no differentiation has been observed—even the
abortus/melitensis forms being unexceptional in this respect. Some of the results of this work are
shown in Table (XXVIII).
TABLE XXVIII
The antigenic sensitivity of Indian Brucella strains
Strain No.
F39
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F40
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F41A . . . . . . . . . . . . . . .
F41B . . . . . . . . . . . . . . .
F42 . . . . . . . . . . . . . . .
F43
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F44 . . . . . . . . . . . . . . .
F45 . . . . . . . . . . . . . . .
F46 . . . . . . . . . . . . . . .
F47
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F48
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Control (European) . . . . . . . . . . . . .
Type
A/M
A/M
A/M
A/M
A/M
A
A/M
A
A/M
A/M
A/M
A
Titre
+ 1/1120
++1/1280
+ 1/1280
+ 1/1120
+ 1/1280
+ 1/1120
+ + 1/1120
+ + 1/1120
+ + + 1/1120
+ + 1/1120
++1/1280
++1/1280
A=Br. abortus
A/M=
Br. abortus/melitensis
Tests for antigenic sensitivity were carried out as follows. Standard antigens were prepared
by suspending in 12 per cent saline 48-hour-old slant cultures of the strains to be examined, their
density being very accurately adjusted to 1 on the Brown's scale. Stableforth's [1936] standard
dried serum was reconstructed according to his instructions, but his final titration series was halved
in saline. In a series of tubes, 0.5 cc. of the antigen to be examined was added to 0.5 cc. of each
dilution of serum in the halved Stableforth series, thus forming a titration range of 1/640, 1/800,
1/960, 1/1120 and 1 1280 and the ultimate reaction after 24 hours incubation at 37°C was noted.
In this range, type specific antigen prepared in a similar way had been previously found to react
to about + 1/1280, and this titre was accepted as the datum with which the end points of the field
strains titrations were compared.
Virulence
As white mice are required in large numbers in assays of virulence, and, as these animals are
difficult to obtain in India, only a small number of Indian Brucella strains could be examined for
this property. The test is described by Priestly and McEwen [1938] and the results of the some
estimations carried out in the present work are shown in Table (XXIX). For purposes of comparison
tests on 3 foreign vaccine strains (V.1 V.4 and V.5) are included in this Table. These tests are mainly
concerned with vaccine preparation and at present it is only desirable to note that they fail to kill
white mice in considerably greater doses than do the field strains, whilst even among themselves
their virulence is graded. Again, for control purposes, it was necessary to compare the virulence
of Indian strains with that of type specific strains from abroad, and in so doing few mice were left
for testing the local strains ; even then the interest centering round the A/M type led to four of these
and only one abortus and one melitensis being examined. At this time, of course, it was not under-
stood that the supply of white mice would fail entirely, due to war.