J. F. SHIRLAW AND P.
R.
KRISHNA
IYER
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vaccine. All four animals were tested for immunity, the first two cattle 50 days p.i. and the other
two 46 days p.i., with 3 c.c. homologous virulent lymph virus subcutaneously at the point of the
shoulder along with one control. The reaction to the test dose was, in all four animals, extreamely
severe, hypersensitiveness rather than immunity having, apparently, been created; death occurred
in every case, as well as in the control animal.
Tail-tip vaccination. In the first test, six cattle were used. Three were inoculated subcutane-
ously about one inch above the tail tip with 0.5 c.c. eitht-day old 8th generation Bennett Broth
culture of the Assam 1 organism. The other three cattle were similarly inoculated, at the same
time, with 0.1 c.c. virulent lymph virus. Both batches were given a reinforcing dose, tail tip,
13 days later, the first lot 1 c.c. of the same culture and the second lot 0.5 c.c. of the same virus, the
materials having been maintained at 5°C. between the intervals of inoculation. In the culture-
inoculated animals no reaction was observed. In the virus-inoculated batch, one animal developed
fever three days before the reinforcing dose was due and reacted so severely that death followed 24
days after the first inoculation. Typical lesions of contagious bovine pleuropneumonia were seen
at post-mortem and the virus from this case was passaged. In a second animal of this batch, inflamma-
tion of the tail commenced two days after the reinforcing dose and increased in intensity for four
days when the lesion ruptured; necrosis slowly developed and the tail sloughed 26 days later. In
the third animal of this batch, inflammation of the tail likewise developed after the reinforcing dose;
four days later the lesion ruptured and healing was complete in nine days. All three animals of
the first batch and the two survivors of the second were tested for immunity fifty-nine days after
the first inoculation, the test dose being 2 c.c. virulent Australian 264 lymph virus subcutaneously
at the point of the shoulder. None of the five animals reacted to the test dose and were solidly
immune, two controls reacting fatally. A second test was carried out with seven cattle. Each
animal was given 0.5 c.c. 6th generation culture subcutaneously one inch from the tail tip and one
month later five of these animals were given a reinforcing dose, by the same route, of 1 c.c. 8th
generation culture. No reaction to vaccination was noted in any of the seven animals and 148 days
after the first inoculation all were tested with 2 c.c. homologous virulent virus, along with 1 control,
subcutaneously at the point of the shoulder. (This immunity test was adopted as standard.) The
control reacted severely but survived and five of the seven cattle tested did not react and were thus
immune to the homologous virus; the remaining two cattle were partially immune. Both reacted
to the test dose with an incubation period of four days, but in neither case was there any systemic
reaction and the local lesion sloughed early. Ordinarily, as we have already noted, sloughing of
the local lesion and absence of systemic reaction is followed by recovery, but in both animals secondary
local sepsis and maggot infestation of the wounds necessitated destruction. The indications were,
in this test, that immunity is conferred with a single dose of culture and that a reinforcing dose is
probably unnecessary. In an attempt to ascertain whether tail tip vaccination with Assam 2 strain
culture could protect against Assam 1 strain virus, three cattle were inoculated tail tip with 0.5 c.c.
5th generation Assam 2 culture; the inoculation was repeated a week later with 1 c.c. 6th generation
Assam 2 culture and 37 days later all three animals were tested with one control with 0.5 c.c. Assam
1 lymph virus. The control reacted severely and died and none of the three vaccinated animals
showed any sign of reaction.
Vaccination with lymph virus stored for 15 weeks at 5°C. It has been shown that the Assam
1 strain lymph virus conserves its virulence at +5°C. for about three months and that there is some
evidence based on test in one animal, that further storage of the material at the same temperature
for three months and twenty-five days resulted in its apparent attenuation. Moreover, the immunity
test of this animal suggested that a virus so attenuated might be of considerable value in vaccination.
This hypothesis was tested in thirteen cattle; ten were subcutaneously inoculated at the point of
the shoulder with 2 c.c. Assam 1 lymph virus stored at +5°C. for 15 weeks, and to test the relative
safety of this product two cattle were given 40 c.c. and one 20 c.c. by the same route, the latter animal
being inoculated ten days after inoculation of the main batch with the same sample of lymph virus
further stored for this period. None of the animals so vaccinated showed any reaction, either local
or general, and all were tested for immunity with two controls 224 days (the last animal 214 days)