350
Equine Encephalomyelitis in India
Others do not, and cystitis cannot, therefore, be looked upon as a primary
lesion of the disease but as essentially secondary. The degree of cystitis which
is present in some cases, the marked induration of the bladder wall and the
early formation of calculus, force one to the conclusion that the vesical paralysis
and retention must have been insidious in its development and even in peracute
cases, apparently normal a few hours previously, which suddenly became
paralysed and died within twenty-four hours, chronic cystitis may be found.
A reasonable explanation of this is that these cases had been undergoing a
slow, insidious, progressive invasion of and damage to vital nerve centres and
it was only when the infection reached the brain in a massive concentration, or
when the damage wrought on the cortical tissues reached a peak, that a crisis
was precipitated with the sudden appearance of peracute symptoms. This
is not an unreasonable assumption when one considers that, in the subacute
and chronic cases the cord is predominantly affected and the cerebral lesions
extremely slight, though definite.
In spite of the marked cystitis frequently present, no case of ascending
pyelitis has ever been encountered. Marked swelling of the spleen appears
a fairly constant lesion. Hæmorrhage from the splenic vessels is occasionally
severe and coalescence of such areas results in the transformation of the spleen
into a vast blood clot with obliteration of the cellular elements.
The kidney lesion is of particular interest. The kidney is enlarged, the
capsule tense, but the substance is not pale in colour or somewhat mottled as
in an acute parenchymatous nephritis. The cut surface possesses a uniform
colour and lines of hæmorrhage may be seen radiating between the tubules,
both of the medulla and cortex. The arterial branches in the pyramids are
sclerotic. This is such a constant lesion in the chronic form of the disease as
to be practically diagnostic when the lesions affecting the central nervous
system are slight, and there is a strong clinical history.
In subacute cases the lesions may be so slight as to escape notice. The
only lesions may be a ground glass appearance of the meningeal vessels, and
punctate hæmorrhages in the grey matter of the brain and spinal cord. These,
as well as the faint hæmorrhagic intertubular striæ in the kidney, may only
be visible with a hand lens. Out of nineteen samples of urine examined, all
were positive for blood and fifteen for bile pigment. The cerebro-spinal fluid
was invariably clear and appeared under pressure.
The difficulties in evaluation of pathological findings during the course
of an outbreak is well illustrated in the Veterinary Officer's experiences during
the outbreak at Sargodha, 1932. Of the seven fillies which died, filly 7804
showed a complete loss of sensation in the quarters and in the perineum and
certain brain symptoms were detected. At post-mortem examination, the
blood was tarry and fluid, the blood vessels of the brain and cord showed in-
tense congestion and numerous petechiæ were present on the bladder mucosa
and the intestine. The temperature of this filly rose to 104° before death.
Filly 8054, ill for five days, showed no other symptom than incoordination and
the only lesion noticed at post-mortem was slight enlargement of the spleen.
Filly 8686, ill for the same period, was similarly affected with slight intestinal
congestion in addition. In both these cases the temperature rose before
death. Filly 8992 showed no lesions at post-mortem. Filly 7987 showed