Rabies - Symptoms and causes Diagnosis Treatment

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.