Rabies :Diagnosis and Negri bodies

Rabies :Diagnosis and Negri bodies


DIAGNOSIS OF RABIES

  • Detection of antigens by immunofluorescence. 
  • The specimens collected are :
  1. Antemortem
  2. Corneal smear
  3. Skin biopsy from neck or saliva
  4. Postmortem
  5. Brain biopsy
  • A definitive diagnosis Negri bodies in the brain or spinal cord.
  • Rabies virus specific antibodies detection in serum and CSF.(devlop late)
  • Two methods are used to detect antibodies
  • Indirect fluorescent antibody test
  • Rapid fluorescent focus inhibition (RFFIT)
  • Reverse-transcription polymerase chain detection of rabies virus nucleic acid in the saliva.
  • It is done during early CNS infection.
  • Virus isolation
  • Isolation of virus by intracerebral inoculation in mice can be attempted from the brain, CSF, saliva and urine 
  • Chances of isolation are greater in early disease.
  • A more rapid and sensitive method is isolation in the tissue culture cell lines (WI-38, BHK 21, CER)

NEGRI BODIES

  • Described by Negri in 1903
  • Negri bodies are practically pathognomic for rabies
  • Composed of fibrillar matrix and virus particles

STRUCTRE

  • Sharply outlined, (2-10 µm in diameter)
  • Intracytoplasmic
  • Deeply eosinophilic inclusions that measures several microns in diameter.
  • Seen in hematoxylin and eosin stained sections.
  • Consists of a mass of nucleocapsids
  • Surrounded by viral particles budding from intracytoplasmic membranes.

SITE OF OCCURENCE

  • Occur in Ammon’s horn of neurons of the brain stem(Hippocampus)
  • Purkinje cells of the cerebellum
  • Can be seen in axons(infection spread from here)
  • Found away from the inflammatory, nonspecific lesions

DETECTION

  • Antigen demonstrated in infected cell
  • Early confirmation
  • Detection by immunofluorescence of biopsy sample
Exam Question
 

DIAGNOSIS OF RABIES

  • Detection of antigens by immunofluorescence. 
  • The specimens collected are :
  1. Antemortem
  2. Corneal smear
  3. Skin biopsy from neck or saliva
  4. Postmortem
  5. Brain biopsy
  • A definitive diagnosis Negri bodies in the brain or spinal cord.
  • Rabies virus specific antibodies detection in serum and CSF.(devlop late)
  • Indirect fluorescent antibody test
  • Rapid fluorescent focus inhibition (RFFIT)
  • Reverse-transcription polymerase chain detection of rabies virus nucleic acid in the saliva.
  • It is done during early CNS infection.

NEGRI BODIES

  • Negri bodies are practically pathognomic for rabies
  • Composed of fibrillar matrix and virus particles

STRUCTRE

  • Deeply eosinophilic inclusions 
  • Seen in hematoxylin and eosin stained sections.
  • Consists of a mass of nucleocapsids
  • Intracytoplasmic membranes.

SITE OF OCCURENCE

  • Ammon’s horn of neurons of the brain stem(Hippocampus)
  • Purkinje cells of the cerebellum
  • Can be seen in axons(infection spread from here)
  • Found away from the inflammatory, nonspecific lesions

DETECTION

  • Immunofluorescence of biopsy sample
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