342           An Outbreak of Equine Encephalomyelitis.

The first outbreak of encephalomyelitis in which a virus was suspected
to be the cause occurred in a cavalry regiment at Multan in the winter of 1933
The disease was investigated by Mosley, Heane and Shirlaw [1934], the last-
named of whom adduced evidence to show that it was very closely related to
the American type of equine encephalomyelitis and that it was probably
caused by a neurotropic filterable virus of organotropic type.

Recently a similar outbreak has been described from Kashmir by Kak
[1937] and the close clinical similarity between this outbreak and the one at
Multan suggests that probably it too was of virus origin.

Within recent years several outbreaks of equine encephalomyelitis have
been reported, mostly from military establishments in the Punjab, and fre-
quent references to it are to be found in the recent reports of the Imperial
Veterinary Research Institute at Mukteswar and of the Army Veterinary
Service in India, but there is nothing to show that the existence of a virus in
these outbreaks was proved.

In this article an account is given of an outbreak of paraplegia, later
diagnosed as encephalomyelitis, that occurred among the Mounted Military
Police horses at Jamshedpur during the winter of 1936-37 and which bore
some resemblance to the outbreaks at Multan and in Kashmir but in which
the existence of a virus could not be definitely proved. An attempt to con-
nect the outbreak with vegetable poisoning also proved abortive, while ex-
amination of the blood and fodder for their calcium and phosphorus contents
did not reveal any abnormality of such an exceptional nature as to justify
any definite conclusions. As a matter of fact, the etiology of the disease has
up to now remained undetermined.

In this connection it is important to note that a similar outbreak has
again occurred among these horses this year (1937-38), the first case occurring
towards the end of October and the last towards the beginning of January.
Of the total number of six horses attacked, four recovered and two are going
to be destroyed. Similar cases of a sporadic nature have also been reported
from among the Mounted Military Police horses at Patna and some privately-
owned horses in North Bihar. These last-named are also Walers except for
two which are country-breds.

The description which follows relates only to the outbreak which occurred
during the winter of 1936-37 except where otherwise specifically mentioned.

                    HISTORY OF THE OUTBREAK

There are five troops of the Mounted Military Police horses in Bihar, of
which three are stationed at Arrah, one at Patna and one at Jamshedpur.
Each troop comprises twenty-eight horses and the troops exchange places
once every year. The horses are all of the Waler breed. The Mounted
Military Police station at Jamshedpur was first established in May 1933 and
the troop in which this particular outbreak occurred had been there since
October, 1935.