RABIES: Laboratory diagnosis
A combination of several diagnostic techniques
is generally used to diagnose rabies.
Fluorescent antibody on brain smears
to demonstrate viral antigen. Results in 2-3 hours, high degree of accuracy.
Histological examination of brain material,
usually from hippocampus, for specific Negri inclusion bodies. Results in 2 days,
but not very accurate and in most countries now superseded by other tests.
Examination of formalin-fixed brain tissue
by immunochemical techniques or, if trypsin treated, by immunofluorescence.
Mouse inoculation: mice inoculated intracerebrally
with suspension of brain tissue, and brains examined by immunofluorescence at
intervals up to 28 day post inoculation.
Cell cultures: in recent years, some
cell lines have been found to be equally if not more sensitive than mouse inoculation
for diagnosis and have now superseded it in many laboratories.
Panels of monoclonal antibodies may be
used in immunofluorescence tests on brain smears or infected cell cultures to
determine the origin of the rabies virus (i.e. vaccine or field, rabies or rabies-related
virus, or which species it comes from, e.g. skunk or fox).
Detection of rabies virus by polymerase
chain reaction (PCR) recently described.
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