22
REPORT OF THE IMPERIAL BACTERIOLOGICAL LABORATORY,
of serum and 115,050 doses of vaccine prepared, and 177,418 doses of
serum and 115,050 doses of vaccine issued during 1921-22.
The figures indicate that there has been a large rather steady demand
for the serum and a greatly increased demand for the vaccine. The
large issue of vaccine is due to the confidence which the veterinary autho-
rities in the Punjab have acquired as the result of field experience in the
efficacy of the vaccine to prevent the occurrence of outbreaks in enzootic
areas if it is injected into susceptible cattle before the advent of the
season of increased prevalence just before the monsoon. Laboratory
experience, so far as it has been pursued hitherto, fully justifies
the confidence of field workers, for a slight increase in an animal's
defences as indicated by a specific agglutination reaction such
as can be induced by the inoculation of a " dead " vaccine increases
its powers of resistance to a virulent attack very considerably. In
other provinces, such as Bihar and Orissa, great confidence has gained
in the efficacy of the anti-serum, and the veterinary authorities there
state that serum intervention in the face of an outbreak cuts dead the
spread of the disease. When one considers that rinderpest and hæmorr¬
hagic septicæmia are much the most fatal scourges of cattle in India it
is a matter for much satisfaction that the laboratory is in a position to
issue products to ward off both these diseases. Until recently, some
hesitancy had been felt in making this declaration as far as concerned
hæmorrhagic septicæmia serum, for the laboratory tests upon its efficacy
had proved rather disappointing when small experimental animals were
used for test purposes. However, it was found that when the large,
naturally susceptible animals—cattle or buffaloes—were used for test,
the anti-serum was capable of inhibiting with certainty the fatality that
could be induced by inoculation of strains of causal organism highly
exalted by passage through the species. Definitive evidence was, there-
fore, obtained that the serum issued from the laboratory was a sure pro-
tective agent in the doses recommended for use in the field. Further,
research work was conducted with the object of expediting the prepara-
tion and cheapening the costs of production of the serum, and these efforts
have proved highly successful. In the face of an outbreak the use of
serum would, therefore, seem to be indicated to cut short the spread of
disease, and field experience seems to show that the curtailment of losses
is not a temporary one as would be expected from the kind of immunity
usually set up by serum protection. It is probable that the passage of
the infection from animal to animal suffers a rude check with the serum
intervention and is not able to regain a footing in the susceptible animals
during the remainder of the morbid season. Nevertheless, a priori,
the application of vaccine before the advent of the season is indicated in
enzootic areas, for the effects are much more durable, and probably
capable of carrying the injected animal quite safely through the risky
period of the year.
In the laboratory, sero-vaccination, performed by the simultaneous
inoculation of anti-serum and a living culture of the virus, has given the
best results for protection is conferred immediately by the serum and the