MUKTESAR, FOR THE YEAR ENDING THE 31ST MARCH, 1933.
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out 6 months after the original vaccination and it is interesting to
observe that all the calves which reacted to the first vaccination, or in
which an infection was proved by sub-inoculation, failed to react to the
second inoculation, while of the five calves which failed to react and of
which the blood sub-inoculations were negative, four reacted more
or less severely to the second vaccination while one remained negative
throughout. The duration of immunity in these animals will be tested
after the lapse of several years.
In order to test the duration of immunity in adult animals after
vaccination with goat virus a number of hill bulls used in connection
with the production or testing of this virus have been selected for test
at yearly intervals. All these animals have had pronounced or severe
reactions. The first group (8) have already been tested after an
interval of one year and all proved to be solidly immune.
2. Purification of Virus from protozoan parasites.—The use of goat
virus as a means to prevent the transmission of protozoan blood para-
sites has received considerable attention, especially in the case of
imported animals, but it may be well to point out here that, while it
is particularly useful in these animals, the use of goat virus by no means
eliminates diseases due to these parasites as serious complications or
sequelae to vaccination in indigenous herds.
Although the figures
available are comparatively few, there is no indication that the incidence
of piroplasmosis following vaccination or serum-simultaneous inocula-
tion with goat virus is reduced to any marked extent. In India the
danger of resuscitation is apparently as great or greater than the danger
of conveyed transmission.
3. Viability of virus outside the animal body. — The increased interest
taken this year in the application of goat virus vaccination in the field
in India has led to an increased demand for this product and has em-
phasised its advantages and disadvantages. The most important of the
latter at the moment appears to be the difficulty of transmitting the
virus in a virulent state from the laboratory or virus producing station
to the point of inoculation in the districts. With the method described
in previous years eight days is considered to be the maximum safe
period between withdrawal of blood and re-inoculation This period is in
many cases insufficient to allow of the direct distribution of virus from
Muktesar to the more remote districts and as in many cases the virus has
become completely avirulent in less than eight days a study of other
methods of transmission has been taken in hand. A certain measure
of success has been achieved in conserving the virus in spleen and brain
tissue in combination with various substances. These experiments are
being continued and have already led to a considerable saving in animals
used for the routine production of virus, as it has been found possible
to interrupt the continuous animal passage of the virus at intervals
with varying periods of storage without inducing any marked alteration
in virulence. At the same time it was observed that in two cases where
material was continuously passaged through bulls or goats at monthly
intervals there appeared to be a well-marked and well-graded attenua-
tion. Further observations on this method of attenuation will be
undertaken.