Rabies :Diagnosis and Negri bodies

The site in the brain that is a favored location for ischemic damage, rabies virus infestation, and toxic damage resulting from alcohol is the Purkinje cells in the cerebellum.

In chronic ischemia, the Purkinje cells undergo apoptosis (individual cell necrosis) and assume a shrunken, deeply eosinophilic cytoplasm with fading out of the nucleus (red neuron). The eosinophilic Negri inclusion body of rabies is located in the cytoplasm of the Purkinje cells. Alcohol has a direct toxic effect on Purkinje cells, resulting in cerebellar atrophy. 

The nucleus basalis of Meynert is associated with neuronal loss in Alzheimer disease. 

Negri bodies

Rabies

Ans. is ‘b’ Rabies Virus & ‘c’ Measles Virus 

Hemadsorption

.                                   When hemagglutinating viruses grow in cell cultures, their presence can be indicated by the addition of guinea pig erythrocyte to culture. If the viruses are multiplying in the culture, the erythrocytes will adsorb on to the surface of cells. This is known as Hemadsorption.

.                                   Viruses causing Hemagglutination are :

– Influenza Virus          – Measles               – Rubella                – Coxsackie Virus         – Rhino Virus        – Rabies

– Parainfluenza Virus   – TogaVirus             – EnteroVirus          – EchoVirus                    – ReoVirus

Diagnosis of rabies

The diagnosis of rabies is usually made by the detection of rabies virus antigens by immunofluorescence. The specimens collected are :

Antemortem                                                                > Corneal smear

Skin biopsy from neck or saliva

Postmortem                                                                  Brain biopsy

Ans. is ‘a’ i.e., Rabies is diagnosed by immunofluorescence

.  Diagnosis of rabies is usually made by the detection of rabies virus antigens by immunofluorescence.

.  Rabies does not cause life long immunity, in fact rabies infection cause death of all patients.

.  Rabies virus is of single serotype only.

.  Rabies Vaccines are killed inactivated vaccines

Ans. is ‘d’ i.e., They do not contain rabies virus antigen

Ans. is. ‘d’ i.e., Fluorescent

The method most commonly used for diagnosis of rabies is the demonstration of rabies virus antigen by immunofluorescence.

Ans. B i.e. Antigen detection by immunofluorescence of skin biopsy

Negri bodies

• They are eosinophilic, sharply outlined, pathognomonic inclusion bodies (2-10 µm in diameter) found in the cytoplasm of certain nerve cells containing the virus of rabies, especially in Ammon’s horn of the hippocampus.
• Often also found in the cerebellar cortex of postmortem brain samples of rabies victims.
• They consist of ribonuclear proteins produced by the virus.

Ans. D i.e. Neuron

Negri bodies are distributed throughout the brain, particularly in Ammon’s horn, the cerebral cortex, the brainstem, the hypothalamus, the Purkinje cells of the cerebellum, and the dorsal spinal ganglia.

Ans. Negri bodies in brain

Ans. is ‘b’ i.e., Corneal smear

Diagnosis of rabies

The diagnosis of rabies is usually made by the detection of rabies virus antigens by immunofluorescence. 

The specimens collected are :

• Antemortem
• Corneal smear
• Skin biopsy from neck or saliva
• Postmortem
• Brain biopsy
• A definitive pathologic diagnosis of rabies can be based on the finding of Negri bodies in the brain or spinal cord.
• Other methods for Rabies diagnosis

i)  Rabies virus specific antibodies detection in serum and CSF.

• But rabies virus-specific antibodies develop relatively late in the clinical course when the patient survives beyond the acute phase.
• Two methods are used to detect antibodies:
• Indirect fluorescent antibody test.
• Rapid fluorescent focus inhibition (RFFIT)

ii)  Reverse-transcription polymerase chain detection of rabies virus nucleic acid in the saliva.

• It is done during early CNS infection.

Negri bodies

Ans. B: Rabies

Negri bodies are discrete, intracytoplasmic, deeply eosinophilic inclusions that measure several microns in diameter. In about 75% of cases of rabies these can be seen on hematoxylin and eosin stained sections.

They occur in neurons of the brain stem, particularly those in the hippocampus, and in the Purkinje cells of the cerebellum. Ultrastructural studies have shown that Negri body consists of a mass of nucleocapsids surrounded by viral particles budding from intracytoplasmic membranes.