Rabies:

Rabies
Rabies infected animal

Rabies Synonym: 

hydrophobia

Rabies Definition:

Viral infectious disease of CNS and is highly lethal viral infection caused by specific type of virus clinically characterized by a variable incubation period from 2 weeks to 16 weeks or longer and for a very short illness i.e. 2-3  days.

Rabies Etiology:


Rabies Causative agent:

lyssa virus type-1
Family: Ribo viradae
Sub-family: rhabdo viradae

Morphological characteristics of Rabies Virus:

It is single strand RNA genome
One end is round and other is flat
Length is 18nm, diameter is 75nm

Types of Rabies virus:

There are two types of rabies virus

  • Street virus 
  • Fixed virus


Rabies Street virus:


  • It is naturally occurring cause of rabies
  • Very lethal 
  • Nor used in vaccine product
  • Incubation period is long.


Rabies Fixed virus:


  • Artificially produced by tissue culture technique
  • It is not lethal 
  • Used in vaccine product
  • Incubation period is 4-6 days.


Reservoir / habitat of infection of Rabies virus:

In urban areas, rabies reservoir is rabid dog
In case of wild life, bats, jackal, fox etc.

 Rabies Source of infection:

All warm blooded animals are responsible for zoonotic infection
Saliva (highly infected with virus) is a source of infection of rabid animals.

Rabies Mode of transmission:



  • Bite of rabid animal

  • Licking of abraded/traumatic skin 

  • mucosal membrane by rapid animal


Incubation period Rabies virus:

 2-16 weeks or longer.

Factors effecting incubation period of Rabies virus:


Site of bite:

If site of bite is towards from CNS then incubation period is short and if away from CNS then incubation period is long.


Severity of bite:



  • Mild 
  • Moderate
  • Deep 
  • Superficial


Number of bites


  • Nature of rabid animal
  • First aid facility


Pathophysiology of Rabies:


  • Inoculation of virus to any other healthy animal
  • Locally multiply or replicated of that virus in connective/muscular tissues.
  • Attachment of virus to inorre ending of peripheral neuron
  • Start moving towards and away from CNS.
  • In CNS it will cause encerptialilits
  • Centrifugally moving towards various areas of the body i.e. skeletal muscles, myocardial muscles and different glands i.e. salivary glands attack on salivary gland is very crucial and a source of infection cause zoonotic infection of CNS and result in death.


Clinical features of Rabies:


  • Prodromal phase/stage
  • Headache, low grade fever and sore throat
  • Pain and tingling at the site of bite
  • Malaise and fatigue
  • Excitation stage:
  • Sensory system involvement
  • Motor system involvement
  • Autonomic system involvement
  • Mental involvement


 Sensory system involvement:


  • Hydrophobia
  • Aerophobia
  • Rigidity and spasticity of muscle 
  • Intolerance of light


Motor system involvement:


  • Rigidity and spasticity of muscles.
  • Autonomic system involvement:
  • Excessive salivation and lacrimation
  • Mental changes/fear of death
  • Depression and anxiety


Convulsion stage:


  • Convulsion/paralysis
  • Coma
  • Death


Diagnosis of Rabies:

  • Neigri body identificatio
  • History of rabid bite
  • Clinical features
  • Immune fluorescent technique.
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Haseenullah Shah

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