350          An Outbreak of Equine Encephalomyelitis

A pony injected by the author locally with 10 c. c. of brain emulsion from
a horse that had been destroyed after a severe illness lasting for about three
months also failed to develop the disease, while an attempt to infect another
pony by injecting it intrathecally and intranasally with 40-50 c. c. of cerebro-
spinal fluid taken from horses involved in the 1937-38 outbreak yielded no
better results.

It will thus be seen that the results of transmission experiments on guinea-
pigs, rabbits and ponies have been too uncertain and inconsistent to justify
any definite conclusions about the virus origin of the malady, though in view
of the known difficulty of transmitting equine encephalomyelitis experi-
mentally, such a possibility cannot be entirely excluded. Nevertheless, one
cannot help thinking that if a virus was the real cause of the trouble the per-
centage of successes should have been greater than that obtained in the ex-
perimental transmission work. It is also well known that in carrying out
experiments with brain tissue great care is necessary both with regard to the
technique and the material used as otherwise quite misleading results may
be obtained.

It is proposed to carry out further experiments when some of the horses
involved in the present outbreak (1937-38) are destroyed.

The possibility of a mineral imbalance as a factor in the etiology of the
condition has not been overlooked and at the request of the Imperial Veteri-
nary Research Institute, Mukteswar, which is engaged in an investigation of
this disease and other similar diseases from this point of view, samples of
serum and fodder were supplied for analysis, but the results so far to hand do
not reveal any abnormality in the calcium and phosphorus contents of these
materials of such a consistent nature as to warrant any definite conclusions.
It is proposed to pursue the investigation from this point of view as and when
opportunity occurs.

While on this subject, the possibility of cold as a probable factor in the
causation of the condition must be mentioned, for it was observed that the
majority of the cases in the 1936-37 outbreak (as also those in the 1937-38
outbreak) were among horses tethered on the side of the stables exposed to
the cold westerly winds, while very few cases were seen among horses tied on
the other side. It is not improbable that cold acts as an important predispos-
ing factor in the causation of the condition, tending to lower the vitality of the
animal and rendering it susceptible to attack by the specific cause whatever
that might be. Support is lent to this view by the fact that in both the out-
breaks which have occurred at Jamshedpur so far the disease has shown a
definite seasonal incidence. The first cases are usually seen to arise about
October or November and the disease tends spontaneously to subside about
February or March with the onset of the warmer weather. The outbreaks at
Multan and in Kashmir also occurred during the colder part of the year though
the exact relationship between them and the disease in this Province has not