PREVALENCE AND PATHOLOGY OF POLIOENCEPHALOMALACIA IN GOATS
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Date
1999
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES-MANNUTHY,THRISSUR
Abstract
Polioencephalomalacia is a significant emerging disease problem in goats
Although, PEM in goats was
disease problem m goats. recognized and reported as early as 1956, its etiology is poorly understood and symptomatolgy, pathological features and therapeutic approach have not been well defined and
documented.
Hence an investigation was undertaken to assess the prevalence of the disease based on the data available from i -F i-hw citate for a period from 1991 76 Veterinary hospitals of to 1994. This data documented revealed an increasing trend to the occurrence of the disease and significantly high o n 4 Pt +-hP first five months of which incidence was recorded m the first
a. amVhcprvpd in the month of April, the peak incidence was observe
spontaneous cases of the disease were studied m
detail and experiments were conducted taking goat as a model using selected incriminating agents such as Amprolium ;350 mg/kg body weight), Amprolium and rice gruel (350 mo/kg, and ad libitum rice gruel), nee gruel (ad libitum), sodium sulphate (150 mg/kg body weight followed by 500 mg/kg body weight on the 10th day) BHC (2.5 mg/kg followed py 5 mg/kg body weight on the 10th day) and Ficus tsiela mOXb. The experiment was for a period of 45 days.
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/-mptomatology, weight of the animals at fortnightly
intervals, weight of the brain, CSF protein concentration.
Drain autofluorescence, gross and histopathological
alterations of the brain and ultrastructural pathology were
the markers utilized for evaluating the disease processes.
The sodium sulphate, BHC and Amprolium and rice gruel
created group showed symptoms and lesions more or less
similar to the spontaneous cases. Only few animals in each
group developed the disease such as two in amprolium and
rice gruel treated group, four in BHC treated group and
chree in sodium sulphate group. This showed that
individual idiosyncracy plays an important role in the
manifestation of the disease.
The symptoms developed at different latent periods
were not progressive as compared to the spontaneous cases
where Che symptoms were progressive. The symptoms included
lethargy, depression, knuckling at the fetlock, frequent
cremors, opisthotonos and loss of eye preservation reflex.
Blindness was seen in one of the, natural cases.
The histological lesions of the brain in all the cases
were comparable in different segments of the brain. Mostly
ic was characterized by diffuse laminar cortical
aeaeneration and necrosis, occasional neuronal swelling,
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giial cell reaction and white matter vacuolation. Vascular
changes predominated in the sodium sulphate group and also
in the natural cases. There was glial cell response in the
form of nodules in sodium sulphate group and natural cases.
A predominant perivascular and neuropil accumulation of
lymphocytes, gitter cells and monocytes were .seen in the
natural cases. These were considered as secondary
deposition following a toxic degenerative neuropathy. The
necrotic focicould well be delineated in few of these cases
by the bluish or creamy autofluroscence of the affected
brain, but was not found to be of any primary diagnostic
value as all the affected brain did not show fluorescence.
Ultrastructural investigation revealed the basic
reaction of the brain tissue to be similar in both the
experimental and natural cases except for their intensity.
Ultrastructural lesions were characterized by neuronal
swelling, membrane lysis, segregation of the filamentous
and granular component of nucleolus, cytoplasmic organellar
aamage such as fragmentation of RER, partial degranulation
of ribosomes, mitochondrial swelling, cristolysis and
lornplete disappearance of organelle. Neuropil spongiosis
and splitting of myelin at the intraperiod line and
firmation of multiple vacuolations of the white matter were •
onaracteristic. From this observations it was clearly
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deiineated that the primary insult was a biochemical one
which caused much damage to the volume control mechanism of
the cell and subsequent cellular damage.
The CSF protein evaluation revealed high protein level
in the spontaneous cases whereas in the experimental cases,
the concentration remained within the normal range
indicating that it has no diagnostic value.
In this investigation it has not been possible to
induce PEM with Amprolium even at a dose rate of 350 mg/kg
body weight and it was proved that amprolium is not a cause
for PEM. Rice gruel ad libitum was found to be tolerated
by the animal except one which showed dullness and
abdominal distension towards the end of the experiment.
Diffuse neuronal degeneration was observed in the brain of
this animal. Based on this observation it was concluded
that rice gruel consumption every day as a component of the
concentrate feed in goats might not cause any detrimental
effects and the problem comes only when it is fed in large
quantities on a single day.
B'^icus tsiela Roxb. though produced vascular damage and
aiifuse neuronal degeneration in one of the experimental
animals, goats were found to be highly resistant to Ficus
r-iela Roxb. toxicity and the variation in the
susceptibility of different species to this toxicity was
brought to light.
From this investigation it was also clarified that sodium sulphate, BHC, rice ^ and amprolium could be initiating agents of PEM under certain circumstances and no single cause seems to be responsible for PEM.
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