D. A. MUNRO
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In the case of pigeons and chickens a good local reaction occurs and this usually takes the form
of an inflammation and swelling of the feather follicles. In adult fowls the reaction is less marked,
and at times almost imperceptible. The results obtained with the dry pigeon-pox vaccine are
summarised in Table II.
(a) In sheep
It will be seen from Table I that out of a total of 14 sheep inoculated with the 'dry' vaccine
that had been preserved in cold storage for varying periods, 11 (78.5 per cent) did not react when
tested later for immunity, though the controls in each case developed the usual pustules following
the virus inoculation. A total of six sheep were inoculated with the wet suspension kept at 42ºF. and
only one of these reacted to the vaccine, showing the remarkable rapidity with which this form of
vaccine loses its potency (Srikantiah, ante). The protective value of vaccine stored at 98.6ºF.
was tested on eight sheep and none reacted to the inoculation, irrespective of the fact whether the
vaccine used was in wet suspension or in the dried form, though six of these were found susceptible
when tested later for immunity. In spite of the small number of tests, these results were considered
sufficiently representative to warrant the conclusion that this temperature was quite unsuitable for
storage of the vaccine and further tests along this line were not therefore proceeded with.
(b) In goats
It will be seen that a total of 18 goats were subjected to immunity test after they had received
the protective inoculation with vaccine preserved at the lower temperature and that only seven
proved resistant to the test. Five of the corresponding controls, however, did not react to the virus
inoculation, so that the results in these cases must be regarded as inconclusive. The results obtained
with vaccine stored at 98.6ºF. were in conformity with those obtained in sheep, for not one of the
goats in this category reacted to the vaccine.
Kolayli, Mavridis and Ilhami [1933] have recommended the utilization of sheep scab in vaccina-
tion of goats and the use of variola virus of goats against pox of sheep, for in either case a benign
form of the disease is produced by the vaccine and, furthermore, according to these authors, ' the
virus of variola of goats is not transmitted by natural contagion from goat to sheep'. A series of
experiments were carried out to test the value of this method of vaccination for both sheep and goats
and the results are shown in Table III.
It will be seen from Table III that ten sheep were inoculated with the specific vaccine and eight
(80 per cent) did not react when later tested for immunity. On the other hand 10 goats were
inoculated with sheep-pox vaccine and only four (40 per cent) proved immune on test. The protec-
tive value of goat-pox vaccine was tested on ten goats and ten sheep and positive results were obtained
in eight (80 per cent) and three (30 per cent) animals, respectively. These results justify the conclu-
sion that though the two viruses are closely allied, neither of them can be used as a dependable agent
for protecting the heterologous species.
(c) In fowls
It will be observed that the vaccine stored for the maximum period of six months at 42ºF. remains
fully potent for fowls and pigeons, whereas a marked deterioration takes place when the vaccine is
kept at 98.6ºF. Tests on the protective value of vaccine in the wet state were not carried out in
this series of experiments for previous experience has shown that the wet vaccine issued to the field
deteriorated rapidly. Besides as already mentioned, such vaccine had been found to be unsatisfac-
tory in the case of sheep and goats. Brunett [1933] also refers to the gradual loss of virulence in
pigeon-pox virus when the latter is suspended in glycerine saline and recommend its storage in the
powdered form, being suspended in saline only when required for use.
INDICATIONS FOR THE USE OF THE VACCINES
Sheep and goat pox vaccines may be used in clean flocks when the disease is known to be in the
immediate neighbourhood in order to limit the spread of infection. In districts where the disease