62
An Outbreak of Bovine Encephalomyelitis
cerebellum and least so in the cerebrum. The condition might thus be re-
garded as a posterior poliomyelitis with encephalic extension.'
EXPERIMENTAL TRANSMISSION
As soon as it became evident that the disease might be due to a virus,
attempts were made to reproduce the disease in experimental animals (cattle,
rabbits, guinea-pigs) in order to isolate the virus and study its nature. In
attempts at transmission, various routes were employed, subdural, subcuta-
neous and intranasal. The results of these experiments are shown in Table II.
From the primary tests shown in Table II, there was evidence that the
disease was in most cases transmitted to rabbits and guinea-pigs. In several
animals, disturbance of the central nervous system was seen during life and
histological examination showed abnormalities in the brain and cord.
Two separate ' strains' , one isolated from cattle and the other from
pony 5B, were maintained in serial passage through rabbits and guinea-
pigs. The bovine strain was transmitted through two series of animals by
subdural inoculation and by intranasal instillation respectively of a 1 per
cent suspension of brain collected at the height of the disease or at post-
mortem. At the fourth passage, an attempt was made by the subcutaneous
and intranasal routes to transmit the cattle strain to two bulls and the pony
5B strain to two ponies, the experimental animals being kept under observa-
tion for 6—10 months. Unfortunately, the results of these tests were nega-
tive. It may be noted, however, that histological examination of brain and
cord from the four experimental animals revealed changes identical with
those seen in the natural cases. Mild but distinct renal congestion was also
noted in sections of the kidneys.
Transmission of the bovine strain by the subdural route and of the pony
strain was stopped at the sixth passage. Transmission of the bovine strain
by the intranasal route was continued up to the fourteenth passage (Table
III). The incubation period in the experimentally inoculated animals varied
between 11 and 152 days. Not all the experimental animals showed nervous
derangement but there was a marked loss of condition which was regarded
as significant. In every instance, attempts at cultivating bacteria from
the brains of reacting animals were negative while without exception charac-
teristic lesions of encephalomyelitis were seen in sections from the brain and
cord. In most of the experimental animals, lesions in the kidneys were also
prominent, viz. hæmorrhages between the tubules and in the region of the
glomeruli due to capillary rupture. The epithelial lining of the tubules was
unaltered.
SUMMARY
An outbreak of encephalomyelitis, caused in all probability by an ultra-
visible virus, is recorded. Five bullocks, one buffalo bull, 12 cows, one
bull-calf and one pony showed clinical evidence of the disease and all of them
died. A description is given of the disease in its clinical and pathological
aspects and of transmission experiments in small animals.
ACKNOWLEDGEMENTS
Our thanks are due to Dr F. C. Minett for valuable suggestions and
criticisms on completion of this work and to Mrs L. H. Shirlaw for help in
preparing this report.