SEPTEMBER, 1948]
JOHN
B.
POLDING
169
optimum vehicle was used, whilst the vaccine sent to Lahore was made with saline. Accordingly,
two more experiments were made. In the first, a saline control was kept continuously at 42°C and
both an optimum and a saline sample were shaken, as before (during the day at room temperature and
stored during the night at 42°C). Another saline sample instead of being shaken was jerked. Jerking
was arranged by securing the bottle containing the vaccine to a strip of copper sheet anchored at
one end only ; the free end of the strip was within reach of a four armed rotor (r.p.m.=150) adjusted
so that each arm struck the sheet in passing. The sheet thus became a slow vibrator and transmitted
vibrations to the vaccine in a manner reminiscent of railway-travel in India.
In this experiment, the greatest death-rate occurred in the saline control; the least in the opti-
mum shaken sample, whilst after the first 24 hours the comparative rate in the jerked saline sample
was considerable (Fig. 10).
In the other experiment (Fig. 11), a saline suspension was kept at bench temperature conti-
nuously, while a saline and an optimum sample were shaken at the same temperature without inter-
ruption for 72 hours. In this experiment there was a noticeably greater death-rate in both the shaken
samples than in the control.
A review of the preceding work forces the conclusion that temperature of storage, age and
agitation cause Brucella vaccines to deteriorate and while the greatest individual contribution to-
wards this end is undoubtedly temperatures higher than about 70°F. the cumulative effect of all is
very considerable. Further, in all tests, the optimum substrate evolved in the earlier work proved
slightly better in most environments, and very much better in extreme environments than did the
saline. Therefore, the technique recommended for the preparation and issue of Brucella vaccines
in India is as follows.
The vaccine strain is to be sown on liver agar pH 6.8-7.0 and incubated for 48 to 72 hours at 37°C.
The growth is then to be washed off in a small measured quantity of optimum vehicle (say 25 c.c.
per roux flask). The yield from sufficient flasks is pooled (one flask is generally sufficient to produce
100 to 150 c.c. of finished vaccine) and a small sample of the pool is tested to get the dilution factor
required to give a density of tube 5 or 6 on the Brown's scale. The pool is diluted accordingly and
bottled.
Where possible, vaccine should not be issued between April and September, but, if it must be
used during this period, not more than 7 to 10 days should elapse between the despatch from Muktes-
war and the cancellation date marked on the bottle. In winter, when routine vaccination should
be practiced, a period of validity of three weeks might be permitted, but, in every event, the instruc-
tions should urge the earliest possible use of the vaccine.
It is also permissible to store vaccine at Mukteswar at zero degrees C. for one or two months
between preparation and issue; it may be noted further, that the easily obtained and less costly
gelatin may be substituted for tryptose in the preparation of the optimum vehicle.
THE PRESENT POLICY OF VACCINATION IN INDIA
At present, vaccination against Brucellosis is recommended when eradication by hygienic control
seems improbable, or it has been tried and failed. As a general guide, vaccination need only be
considered when farms have an abortion rate of more than 5 per cent of the breeding stock per annum
and conditions adverse to hygiene control (p. 157) exist. The class of stock to be vaccinated may be
selected to suit local convenience, the primary object being to protect all healthy females both
existent and to come. The first group of vaccinees that usually presents itself is existing uninfected
adults and, because these must be inoculated when not in-calf, the work becomes troublesome as it
entails the vaccination of two or three cows at a time as they accumulate after calving. It usually
also means vaccinating in-milk animals, which causes a small but not, it is to be noted, permanent
drop in the milk-yield. Therefore, if only a few uninfected adults remain in a herd, it is for considera-
tion, whether it is worthwhile vaccinating them. Where, however, a number remains, vaccination