Acute Viral Encephalitis Caused by Arbovirus
Background Gross Pathology Histopathology & Immunohistochemistry
BACKGROUND AND CLINICAL INFORMATION:
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Summary: The encephalitis caused by arboviruses are very similar in histopathology. Identification of the infectious agent is necessary to make the correct diagnosis. A variety of arbovirus including alphaviruses, eastern, western, Venezuelan, St. Louis encephalitis, Powassan virus encephalitis, California encephalitis, Japanese B encephalitis can cause encephalitis. List of arbovirus
Venezuelan
type
is more severe in children, most common in South and Central America.
St
Louis encephalitis:
all part of U.S.A. esp. along Mississippi river.
Western
encephalitis:
west of Mississippi River.
Eastern
equine encephalitis:
Endemic
regions:
extends from the costal areas from Florida to Massachusetts, and both
human and equine disease can develop between July and October. The infection
is maintained by an enzootic cycle involving birds and the Culiseta
melanura mosquito.
Mortality:
It is associated with the highest mortality rate among the abroviruses.
Age:
usually affects those below 15 years or over
the age of 55.
Radiology:
CT scans are normal in about half of the cases and occasionally show only
focal lesions.
Clinical
symptom:
patients usually have influenza-like prodrome, with fever, headache,
vomiting, and malaise, which usually progress to convulsions, and coma.
CSF:
Eastern equine virus most frequently induces a neutrophilic pleocytosis.
Anatomic
locations:
Global
involvement, however, the cerebellum, brain stem, thalamus, hypothalamus, and
deep gray matters may be most severely involved.
HISTOPATHOLOGY AND IMMUNOHISTOCHEMISTRY:
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Severe
meningoencephalitis with PMN infiltration, vasculitis, necrosis, and fibrin
deposition on the vessel wall.