J. F.
SHIRLAW
301
EXPERIMENTAL
A preliminary study of ' Lahore Canine Fever' revealed the essential
lesions in the reticulo-endothelial system, notably spleen and bone marrow,
with an active erythropoiesis in these tissues. It has been mentioned that, in
a small minority of cases, P. gibsoni suddenly made its appearance in the peri-
pheral blood, and in a transient fashion, frequently towards the termination of
the disease. As such cases were maintained in tick-free dog kennels, it was
unjustifiable to assume an intercurrent infection as an explanation of the pheno-
menon. Moreover, as the symptomatology and haemocytology of these cases
which had, perforce, to be acknowledged true gibsoni infections ran a course
parallel to true 'Lahore Canine Fever' in which no parasites could be deter-
mined, and as the essential pathology was similar, a suspicion led to the possibi-
lity that' Lahore Canine Fever ' is, in actuality ' tick fever ' due to P. gibsoni.
It became necessary, therefore, to study the syndrome and pathology of
dogs artificially infected with P. gibsoni.
The chief difficulty lay in obtaining suitable experimental animals. The
reaction of the adult pariah dogs obtained from Lahore city, when inoculated
with P. gibsoni, is erratic. In a few cases, the inoculation of blood containing
P. gibsoni resulted in a P. canis infection. The source of the P. gibsoni blood
used in the transmission experiments was a European owned dog which never,
at any time, during observations over seven months, showed any P. canis in its
blood. As P. canis is always easily demonstrable when present, the assump-
tion is valid that this parasite was not introduced accidentally into the experi-
mental dogs along with the P. gibsoni. The only explanation that seems to
offer a solution is that the experimental dogs were naturally, if latently, infect-
ed with P. canis and that the introduction of P. gibsoni flared up the infection.
A considerable number of dogs entirely failed to react to the infection. It must-
be mentioned that experimental dogs were observed for two weeks prior to
inoculation and were maintained in positively tick-free kennels.
It quickly became evident that, if any progress were to be made with the
investigation in hand, experiments would require to be conducted on puppies
that had been reared in tick-free kennels. It was considered necessary, in
view of the racial immunity factor, to use dogs of a pure imported strain, but
as this proved an obstacle, the pups used for experiment were from pariah
bitches and cross-bred dogs, in one case, a pure bred dog. By this method,
it was possible to secure several litters from which the best pups were selected
and sixteen puppies were put to experiment.
These were all artificially infected in course of time. The majority were
used in experimental treatment but seven remained untreated for study of the
natural disease.
Puppies Nos. 3 and 4 were subcutaneously inoculated with 2.5 c.c.
virulent blood and failed to react over a period of observation of two months.
Puppy No. 13 was inoculated on 25th June 1935 with virulent blood and failed
to react. One month later it was inoculated with 5 c.c. spleen emulsion in
F