NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
204 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, III
Two attempts were made in the lines to pass on the disease from one animal
to another.
(1) By removal of spinal fluid taken from a horse in the acute stage of the
attack and inoculating into the spinal canal of a healthy animal.
About 2 c.c. of spinal fluid was removed by means of an intrathecal needle,
from a case in slings at the time. An experimental horse was then thrown by
means of side lines and the 2 c.c. of spinal fluid injected intrathecally. This failed
to set up the disease.
(2) Another experimental horse was placed alongside a recent acute case in
slings and watered from the same bucket. Saliva was also transferred at intervals
to the healthy horse's mouth and grass given contaminated by urine from the
affected case. This also failed to communicate the disease.
In two cases, acting on the supposition that possibly an increased production
of cerebro-spinal fluid might account for the disturbance of co-ordination I removed
with an intrathecal needle 50-60 c.c. of spinal fluid in each case, but without
effect.
On the 2nd February systematic taking of evening temperatures of all horses in
the Regiment was initiated on the recommendation of the D. V. S. in India.
As a result an interesting feature in the nature of the disease came to light.
It revealed that in a certain percentage of cases and possibly in all, the symp-
toms of paresis are preceded by preliminary phase of pyrexia lasting from 2 to
4 days followed by a return to normal 1 to 2 days before the onset of actual
symptoms of paralysis.
Soon after temperature taking commenced, cases of fever occurred at irregular
intervals amongst the horses of " A " squadron only. Altogether 10 horses showed
temperatures varying from 102°-106° F. As each case of fever was discovered
it was isolated. Of these 10 cases, 6 subsequently developed encephalo-myelitis
in the manner described. It would seem probable that the other 4 were infected
but not sufficiently severely to set up clinical disturbance.
These were the last cases to occur in the Regiment.
The fever was not accompanied by any systemic disturbance whatever and the
only abnormality noticed was some injection of the conjunctival mucous membranes
and in all cases which developed the disease, swelling of both hind fetlocks.
Blood smears from all these cases were examined daily with negative results.
ENCEPHALO-MYELITIS IN AN INDIAN CAVALRY REGIMENT
205
Had cases continued and this preliminary fever found to be a constant factor,
the method of control would have been very much simplified. Again, had further
cases occurred it was intended for the purpose of definitely determining whether
or not serum had any protective value, to regard any rise of temperature as a
premonitory symptom of the disease and give each one 200 c.c. of serum either
subcutaneously or intravenously.
It is just possible that the virus may be present in the blood stream only
during this febrile period and thus making the animal infective to others only at
this time, which might account for the difficulty of infecting a healthy animal from
a diseased one by experimental methods.
It was unfortunate from the investigation view point, that the outbreak ceased
just at a time when the clinical study of the disease had reached an interesting
stage.
Local conditions of climate and humidity may have some influence on the
activity of the virus and cold and dampness would appear to enhance its virulence.
More cases occurred during the real cold weather and when there was dew than
at other times. The very large majority of cases were discovered in the early
mornings. The disappearance of the disease coincided with the beginning of
warmer weather.
The question of whether or not immunity is developed is interesting. It is
not determined but the fact that all cases which did not end fatally to all appear-
ances recovered completely and that none have shown any sign of relapse seems to
lend weight to the supposition that immunity is set up and that in consequence
the serum has some clinical value.
The possibility of recovered cases being " carriers " cannot be ignored.
III. PATHOLOGICAL INVESTIGATION OF DISEASE IN HORSES OF THE
13TH LANCERS AT KHANEWAL AND MULTAN.
BY
J. F. SHIRLAW, M.R.C.V.S.,
Professor of Pathology and Bacteriology, Punjab Veterinary College, Lahore.
The report deals with the complete investigation into the outbreak of para-
plegia affecting the horses of the 13th Lancers. Mention is made of the initial
steps which have been taken to make an attempt to arrive at a diagnosis, and the
206 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, III
writer is in a position to record some very accurate information concerning the
essential nature of the disease and an account of the various steps that have
been taken to establish a diagnosis.
Throughout the course of this outbreak, the writer has regularly. received such
pathological tissues as he considered necessary, and a detailed post-mortem account
of every horse that either died or was destroyed in extremis.
It was decided, as an initial step, to obtain the most accurate information
possible concerning the post-mortem appearances, and secondly, the essential tissue
changes occurring throughout the organs.
In all, 14 horses were subjected to a post-mortem examination ; the numbers
of these horses are H. 156, H. .159, H. 332, H. 282, H. 149, H. 42, H. 513, H. 88,
H. 103, H. 515, H. 288, H. 416, H. 286, H. 312. It can be definitely stated
that the macroscopic appearances were practically identical in every case. The most
striking feature of the post-mortem examination is the relative absence of any gross
pathological picture. In one or two cases the pathological findings might, to a
casual observer, be termed negative. In the majority of cases, a mild catarrhal
inflammation of the gastro-intestinal tract was noticed. The parenchymatous
organs appeared to contain more blood than normal without any evidence of an
inflammatory process. The spleen seemed slightly softer in consistence but was
not distended. The kidneys appeared superficially normal, but on mesial section
streaks of hæmorrhage radiating from the medulla were found. The bladder
contained, in most cases, urine of an altered character. In some cases this was
thick and syrupy in appearance and contained much sediment; in other cases the
urine was full of blood. The bladder wall, in nearly every case, showed more or
less extensive hæmorrhage in the mucous coat. In one case a severe hæmorrhagic
cystitis was present. The presence of a straw coloured fluid in the peritoneal and
the pericardial sacs was described in a few cases. This fluid was free of cells,
contained no bacteria, was poor in fibrin and appeared more of the nature of a
transudate than an exudate. The lymph glands were moderately swollen and in
some cases showed hæmorrhages.
The most typical features of the disease were found in the brain and spinal
cord. A superficial examination intimated the presence of a meningitis, but on
more critical examination it was seen that the lesion consisted of an abnormal
fulness of the vessels of the meninges and of the choroid plexus, without the presence
of any exudate in the meningi. The cut surface of the brain showed hæmorrhages
in the cerebral cortex, especially in the area of the choroid plexus. Punctate
hæmorrhages were observed throughout the brain substance and in the brain stem
as well as in the cortex. In many cases these hæmorrhages were extensive, and
ENCEPHALO-MYELITIS IN AN INDIAN CAVALRY REGIMENT
207
extended to a depth of several millimetres below the meninges, separating this
membrane from the ependyma. In one case, a true meningitis with the presence of
an exudate in the meninges was noted. The spinal fluid was in every case clear
and was not increased in quantity, and on examination there was no increase
in cellular content. The fluid appeared blood-tinged in one or two cases,
but this was probably caused by the accidental rupture of capillaries.
The presence of bacteria could not be detected in this fluid from any case, either by
direct microscopic examination, or by selective cultural methods.
The spinal cord showed either extensive or patchy hæmorrhage under the
meninges, hæmorrhages extending for considerable depth round the nerve roots,
and in some cases, a gelatinous exudate under the duramater.
It will be seen then, that the most important lesion consisted of what might
be termed a sub-acute inflammation of the brain, spinal cord and coverings with
hæmorrhages of varying intensity occurring chiefly under the piamater.
BACTERIOLOGICAL EXAMINATION.
The following materials from post-mortem cases were examined in every
case:—
(a) Brain
(b) Spinal cord.
(c) Spinal fluid.
(d) Blood.
(e) Liver.
(f) Spleen.
(g) Kidney.
(h) Bladder.
(i) Urine.
Tissue films were prepared from all these organs and tissues, and in no case
could any bacteria be detected. The exudate which was found in the cord proved
to be negative on examination. The culture media used were :—
(a) Blood agar.
(b) Coagulated blood serum.
(c) Marmorek serum medium.
C
208 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, III
while sterile tubes containing fluids such as blood and cerebro-spinal fluid were also
incubated after cultures had been made. In four cases a streptococcus was
obtained, similar in type in all cases. This organism was definitely haemolytic
and easily obtainable in pure culture from the brain pulp of the four cases.
Further experiments were carried out with pure broth cultures of this organism
to test out its virulence in small laboratory animals and in horses. Rabbits proved
very susceptible to inoculation, dying within 48 hours. One horse was selected for
massive repeated intravenous inoculations of pure broth culture and showed no
effect whatever. The most striking feature of the disease, therefore, is the absence
of any bacteria which could be considered as of etiological significance. A similar
examination for protozoan parasites was negative.
TRANSMISSION EXPERIMENTS.
These were commenced simultaneously with the main pathological examina-
tions. One college horse was inoculated with 5 c.c. of blood removed at post-
mortem from horse No. 156, post-mortemed by the writer on the 28th November
and a second horse was inoculated with 5 c.c. of cerebro-spinal fluid from the same
case. No reaction followed and it was found impossible to transmit the disease by
this method. At this time some considerable suspicion attached to the feed of the
affected animals, and it was decided to observe the effect of feeding experimental
animals such as rabbits and guinea pigs with the stomach ingesta of animals that
had succumbed to the disease. A second part of this experiment consisted in feed-
ing similar animals on bajri (Pennisetum typhoideum) and wheat that had been
soaked in the large intestinal contents of diseased animals. This experiment was
carried out for a period of fifty-six days. All these animals remained healthy.
The possibility of forage poisoning was then considered, and work was undertaken
in conjunction with the Chemical Examiner to the Punjab Government, to elucidate
this possibility. An examination of the stomach ingesta of diseased animals proved
consistently negative for group alkaloid tests. In two cases. arsenic was detected
in such specimens. This finding was rather startling, as no source of such poisoning
could be traced. It was reported, however, by the Chemical Examiner, that the
amount of arsenic present could not be held responsible for any disease symptoms.
About this time, as the result of histological examinations of the brain suspicion
attached to the possibility of a filterable virus being the etiologic factor, and as the
lesions of the disease were chiefly confined to the brain and spinal cord which had
proved sterile on bacteriological examination, it was decided to attempt the trans
mission of the disease to experimental animals with brain material. It became the
routine, therefore, to preserve the brain and spinal cord from all post-mortem cases
ENCEPHALO-MYELITIS IN AN INDIAN CAVALRY REGIMENT
209
in 50 per cent. glycerine. These specimens were despatched to the laboratory with
all possible speed, and saline suspensions were made from these tissues and inoculated
subdurally into rabbits and guinea pigs. Rabbits have proved quite refractory
to this experimental inoculation and two guinea pigs inoculated died without
symptoms. These experiments indicated that the disease could not be transmitted
to experimental animals of this type with the exhibition of nervous symptoms,
characteristic of the disease in horses.
One of our college horses was inoculated intrathecally with 2 c.c. of
cerebro-spinal fluid from an acute case of the disease that had been destroyed in
extremis. At the time of inoculation a similar amount of fluid was removed from
the experimental case to avoid any intracranial pressure, which might be likely to
produce fallacious results. Within 24 hours, this horse showed definite signs of
malaise and in 36 hours showed signs of hyperaesthesia, inco-ordination of
movement and general symptoms of meningitis. The fluid injected was bacteriolo¬
gically sterile. There was no elevation of temperature, and the injection had been
performed without any apparent injury to the cord or its coverings. The symp-
toms abated within three days, but a definite inco-ordination was noted for some
time after. The interpretation of this experiment is rather difficult. If the symp-
toms of meningitis had been caused by injury at the time of inoculation, one would
have expected to find them of a more intense nature, and of a more protracted
duration. A possible explanation is that certain toxins were present in the fluid
and that these were responsible for the manifestation of disease symptoms which
were strictly comparable with those observed by the writer in naturally occurring
cases at Multan.
This experiment was repeated upon two horses with entirely negative results.
The most striking and important inoculations performed on experimental horses
were those in which brain emulsion prepared from an acute case of the disease
that had been destroyed in extremis was used. Three horses were used in this
experiment. These horses were army casters in good condition and were sound in
health and action. The first horse was trephined and was inoculated into the
duramater with a few drops of the saline brain emulsion. The second horse was
inoculated subcutaneously in the area of the left temporal plexus and the third
horse was inoculated with 1 c.c. of the more fluid portion of the brain emulsion
intrathecally. These inoculations were performed on the 11th January, 1934. The
horse inoculated intradurally showed definite symptoms of inco-ordination of
movement on 30th January, and on the same day the horse inoculated in the
temporal region showed a similar inco-ordination of movement of the hind limbs, of
a more exaggerated type. The third horse failed to react. This inco-ordination
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210 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, III
gradually became progressive and for some little time hyperasthesia with loss of
the ocular reflexes was noticed in the horse that had been inoculated intradurally.
The inco-ordination consisted of a loss of power in the extensor group of muscles
of the hind limbs. Both animals showed a peculiar dragging movement of the
hind quarters, difficulty in turning, crossing of the feet, and, in short all the typical
symptoms of the disease which had been noted by the writer at Multan.
These horses were destroyed by chloroform on 5th April 1934 and tissues were
removed from them for examination. At the time of destruction the horse
inoculated in the temporal region was showing slight inco-ordination, while the horse
inoculated intradurally was sound in action. It can be deduced from this import-
ant experiment that, by this method of inoculation, it was possible to reproduce the
disease in a mild form in the horse. A definite incubation period of 19 days elapsed
between the inoculation and the development of symptoms, and the fact that both
horses developed symptoms on the same day is of further importance.
ESSENTIAL PATHOLOGY.
The chief feature of this consists of hæmorrhages in the parenchymatous
organs with very slight changes in the structure of the organ. In about half the
cases examined, these hæmorrhages were unaccompanied by cellular degeneration,
and it is probable that apparent degeneration is caused more by post-mortem
changes which are always rapid under tropical conditions. A great difficulty in
obtaining fresh tissue is caused by the simple fact that the tissue commences to
decompose at a rate quicker than the infiltration of the fixative used. These fixa-
tives were of the picric or bichromate series and are rapidly acting, and yet, in
spite of their use, cellular fixation was not sufficiently good definitely to establish
the important point whether parenchymatous degeneration does occur. The most
important pathological change, one which is expressed throughout all the tissues,
is in the blood-vascular system, and it is due to these changes that hæmorrhages
occur. The change consists of a sub-acute endarteritis which is slowly progressive,
and results in a thickening of the arteriole and a narrowing of its lumen. The process
extends through the intima and a coarse thickening of the fibrous coat of
arterioles occurs. Thrombosis is occasionally seen. The change affecting arterioles
is accompanied by a venous stasis. The veins become so abnormally full
of blood that they spontaneously rupture, causing interstitial hæmorrhage, which,
in highly vascular organs like the spleen, are very extensive. So complete is the
break-down of the vascular system of the spleen, that slices of spleen after fixation
in 5 per cent. formaline appear like blood clots, being tough, and of a leathery
consistense. The hæmorrhages in the meninges may be either slight or
ENCEPHALO-MYELITIS IN AN INDIAN CAVALRY REGIMENT
211
extensive. They are constantly present; and may extend under the piamater,
in the choroid plexus, and to a considerable depth, through the sulci of the
brain. These hæmorrhages are constant throughout the cut surface of the
brain, and may be seen in the olfactory lobe, the pons, thalamus and the
brain stem as well as in the cerebellum. In the spinal cord, hæmorrhages extend
around the nerve roots. They may be under the duramater or more commonly
under the piamater. extending for a considerable distance. The nerve roots may
be so densely infiltrated by the hæmorrhages that pressure necrosis of the nerve
elements may be seen. A study of these lesions convinces one that the nervous
symptoms of the disease are partly due to these hæmorrhages occurring within or
around important nerve structures.
The most informative fact about the disease is obtained from a microscopical
examination of the brain. The capillaries and arterioles of the choroid plexus and
its branches in the cerebral cortex are thickened, and in the majority of cases
there is a definite perivascular infiltration of mononuclear cells, this infiltration
extending into the neuroglia cells. In the minority of cases this infiltration or
" cuffing " of the arterioles and capillaries is not so well marked, but in these cases,
there is an extensive, diffuse infiltration of the neuroglia. There is a degeneration
of the nerve cells in the cerebral cortex and a degeneration of the cells of the
cerebellum (cells of Purkinje). The degeneration affects chiefly the nuclei of the
cells. The general appearance of the microscopic lesion in the brain tissue is very
similar to that described in infections with neurotropic viruses, the only difference
being that in the latter disease, hæmorrhages are not encountered and intranuclear
inclusions known as " Joest-Degen " bodies are found. In this disease such bodies
have only been seen doubtfully in one case. It is noteworthy in this connection
that most of the cases were acute, whereas in cases of Borna disease the symptoms
of the disease are of longer duration. In examination of a few cases a definite
meningitis with exudation was present. This lesion was more common in the
spinal meninges.
Most interesting lesions were found in a horse which had recovered from an
acute and serious type of the disease. This horse, after recovery, appeared
perfectly normal, and as a point of interest it was decided to perform a post-mortem
upon it. Hæmorrhages were present in the parenchymatous organs. The
meninges were grossly thickened and adherent.
Extensive perivascular infiltration was present aronud the vessels, and
throughout the neuroglia; the nerve cells of the cerebral cortex showed degenera-
tion, while persistent hæmorrhages were present in the grey matter of the brain
around the choroid plexus.
212 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, III
On such findings, the apparent sound health of the animal and the freedom
from nervous complications seemed a striking feature.
The disease appears as a specific meningo-encephalitis of the horse. This
disease, or a disease of a similar nature, has been described in many countries:
and on a review of the literature pertaining to meningo-encephalitis of the horse,
the outbreak which occurred in the horses of the 13th Regiment bears a very
striking similarity, to those outbreaks recorded in America, in which country
serious epidemics of the disease have occurred. It is only in the last decade that
any attempt has been made in America to elucidate the essential pathology of this
disease. Previously, it had been considered in some way associated with the
feeding of the horses.
In Europe generally, and in Germany especially, a similar disease has been
known for many years, for at least a century—so called enzootic cerebro-spinal
meningitis or " Borna" disease. This disease is enzootic in areas, tending to
assume epizootic characters, and in such infected areas, cyclic incidence occurs at
intervals of every few years. The incidence seems controlled to some extent by
climatic factors. The disease appears infectious, although one of its most
striking peculiarities is that it does not spread in the same way as infectious
diseases usually do. During the course of an outbreak, animals may become
infected in batches, and, when breaking out on a horse-breeding farm, may
occur only on one part of the farm. In certain outbreaks, only one or two animals
may sporadically be affected, and the disease may tend spontaneously to disappear
without any further spread, while in other outbreaks, the disease may sweep
through the horses assuming the proportions of a veritable epidemic with a high
rate of mortality. In American outbreaks, mortality averages about 40 per cent.
and may be much higher.
Very little is known concerning the transmisssion of the disease under natural
conditions. Infection is possibly by way of ingestion, but a very strong suspicion
attaches to the nasal passage as an atrium of infection. Infection seems pre-
disposed to by a mild gastro-intestinal catarrh. Drinking water has been found to
convey the infection, and small animals such as rats, squirrels, mice, rodents
generally, and even birds, are susceptible to the virus of the disease. There is a
strong tendency to incriminate them as carriers during the course of an outbreak.
Although it has been a fashion to designate this disease as forage poisoning,
all attempts to prove the etiological significance of fodder have failed. A very
strong suspicion attaches to the possibility of recovered cases of the disease acting
as carriers. The most certain way of infecting horses, experimentally, is by way