342
Equine Encephalomyelitis in India
temperature recording of all incontact horses was adopted, towards the end of
the outbreak, ten horses suddenly developed pyrexia. Five of these—the last
five cases in the regiment—developed equine encephalomyelitis on the abate-
ment of fever, a few days later. It is considered probable that if temperatures
had been recorded at the beginning of the outbreak, more cases of this nature
would have been discovered. In this, and in later outbreaks, a similar phase
has been noted and one is led to believe that in acute encephalomyelitis, the
disease is ushered in by a transient pyrexia and that all infected horses do not
proceed to a manifestation of symptoms. In fact the wide variation in syn-
drome seen in the Multan outbreak, is capable of explanation on the assump-
tion that, once infected, cases vary in symptomatology between no-reaction,
mild, and severe reaction, as in human poliomyelitis.
On the cessation of the outbreak, the regiment proceeded to Jullundur.
One year later, three cases, horses Nos. 62, 233 and 527, were noticed ' weak in
the loins '. 233 was a pyrexia case at Multan and 62 and 527 had mild para-
plegia at Khanewal in November, 1933. All three had gone down under their
riders and been made to rise with difficulty, shivering and trembling and
scarcely able to return to stables. Within a few days, a typical paraplegia
developed with marked incoordination of movement. The tail was held high
and laterally retracted and constant dribbling of urine (vesical paralysis) was
noted. The posterior quarters were insensitive to forceful pin pricks and
phases of slowly abating hyperæsthesia could be readily invoked. The ocular
reflexes were poor and spasmodic twitching of groups of the face, ear and
cervical muscles was evident. The nerve tissues of these animals were sub-
sequently utilised for transmission experiments in small animals. With this
minor recrudescence, the disease in the regiment was considered to have cleared
up (May, 1935).
In January 1936, however, the disease suddenly flared up again. For a
few days prior to onset, there had been some rain and a sudden fall in tem-
perature. The outbreak lasted for about ten weeks, during which time minor
waves of the infection swept over the horses, and at the beginning of the warm
weather, the disease cleared up spontaneously. Eighteen cases had occurred,
three had been destroyed and one died.
A peculiarity of this outbreak—the second to be critically observed in all
its features—was a decided tendency for independent sporadic cases, with no
apparent relationship or contiguity, to occur at irregular intervals of a few
days. The disease was of a mild nature in comparison with the Multan out-
break. Only three cases developed marked cerebral symptoms. The remain-
der might easily have been termed enzootic spinal paraplegia with a tendency
to cerebral involvement.
It was, however, a definite outbreak of equine encephalomyelitis. Three
cases showed undoubted clinical symptoms and all cases the specific lesions
of the disease after death. It was further observed, during the course of this
outbreak, that a considerable number of cases developed pyrexia, followed,
in one or two cases, by the onset of symptoms with the remission of fever. In
brief, all the epizootic factors and clinical details observed in the Multan out-
break were further substantiated as being illustrative of a field outbreak of
equine encephalomyelitis.