J. F. SHIRSAW AND P. R. KRISHNA IYER 207
save in continental countries where the losses incurred by the method are presumably justified by
the results as a whole. The modification of the method is free from any objection, so much so that
it has been reported from Assam that cattle so vaccinated are in no way incapacitated from full
work, which is a very pertinent consideration in India. If vaccination camps staffed by competent
men can be provided, and cattle owners be persuaded to bring their cattle for vaccination, the method
is one that could immediately be put in operation. Otherwise, any method of vaccination that
entails the use of a fragile culture vaccine is inoperable. It is conceivable that this difficulty could
be overcome by the use of lymph virus attenuated by storage at 5ºC. One virus producer will yield
sufficient vaccine to immunize over 1,000 head of cattle at a trifling cost, and the upkeep of labora-
tories and trained personnel, which would be necessary if the first method were generally adopted,
could be dispensed with. Lastly, very little attention has been paid by workers to the possibility
of an antitoxic immunity. Nocard [1898] observed that, when the organism of pleuropneumonia
was grown in collodion sacs placed in the abdominal cavity of rabbits, these animals usually became
cachectic and died. Since no lesions were present at autopsy, and the organism could not be isolated
from any of the tissues, this worker concluded that the phenomenon was due to the diffusion of toxins
through the collodion membrane. At the same time, he commented on the fact that the rabbit
is quite refractory to infection with virulent cultures of the organism. Sabin [1938] states, in refer-
ence to the foregoing observation, 'in keeping with this is the observation that cattle may die after
subcutaneous injection of infected lymph or culture, although the only lesion is at the site of inocu-
lation ' and comments on the fact that the possible production of an exotoxin by the bovine pleuro-
pneumonia organism is a neglected field of study, especially since it has been lately shown that at
least one other member of the genus produces a true toxin in vivo and in vitro. Curasson [1936]
comments that the problem has never been really studied, and quots the work of Arloing [1888],
who claimed to have isolated, from lymph virus, a relatively thermostable toxin with a specific effect
on bovine tissues. Certainly, no work has been done, in our knowledge, on the feasibility of an
antitoxic immunity. In one experiment recorded in this paper, three cattle were subcutaneously
inoculated with a Berkefeld N filtrate of virulent lymph, no reaction ensuing. Twenty-four days
later, these animals were put to a standard immunity test and none proved immune. The experi-
ment was repeated in two cattle, but in this case the immunity test was delayed for 112 days, both
animals proving solidly immune. In this experiment there are three factors to consider, (a) the
pleuropneumonia organism does not, in our experience, pass a Berkefeld N filter, (b) further proof
of this is the negative reaction in cattle subcutaneously inoculated with such filtrates (c) immunity
develops slowly, the time lag being apparently parallel with the virulence of the vaccine used [Pur-
chase, 1939]. It is possible that an antitoxic immunity was established in animals used in the second
test and the evidence so obtained indicates that a full investigation into this aspect of the problem
of immunity might be well repaid.
SUMMARY
1. Contagious bovine pleuropneumonia exists in the province of Assam.
2. The two strains of virus that have been studied show an immunological relationship with
each other and with strains received from Australia and Kenya.
3. The Assam virus when inoculated subcutaneously at the point of the shoulder in Kumaoni
cattle causes 90 per cent mortality, specific lesions, hitherto undescribed, in the spleen and the abo-
masum, and, in some cases, pleuropneumonia.
4. The Indian buffalo seems insusceptible to the disease in the field and of two buffaloes sub-
cutaneously inoculated with fully virulent virus, one reacted and recovered. The goat is slightly
susceptible to subcutaneous inoculation with the virus and sheep refractory and small laboratory
animals resistant.
5. The virus uniformly passes a Berkefeld V but not a Berkefeld N filter. It will also pass L3
and L5 but not L7; occasionally it passes a Seitz E. K. filter.
6. Immunity experiments with formalinised virus vaccine gave negative results. In two im-
munity experiments with a muscle powder vaccine attenuated by exposure to 70ºC, for 2 hours or
C