Rabies :Transmission and Clinical features

RABIES

• It is the communicable disease which is always fatal.(100% morality)
• Rabies is an enzootic and epizootic disease of world-wide importance.
• Diseases under international surveillance (WHO)

DISTRIBUTION

• Geographic boundries play  role in the distribution of rabies.
• Water appears to be the most effective natural barriers to rabies.
•  In India, Lakshadweep and Andman & Nicobar islands are free of the disease.
• A Rabies free area has been defined as one in which no case of indigenously acquired rabies has occurred in man or any animal species for 2 years.
•  Countries where rabies is not found  

1. Australia 
2. China (Taiwan),
3. Cyprus
4.  Iceland
5.  Ireland
6.  Malta
7.  Japan
8. Newzealand,
9. Britain.

MODE OF TRANSMISSION

• Bite of rabid dogs or other animals (Most common)
• Non bite exposure

1.   Licks or aerosols
2.  Transplantation of cornea.

PATHOGENESIS

• Enters the peripheral nervous system (PNS) directly
• Migrates to the brain.
• It replicates within muscle tissue, where it is safe from the host’s immune system
• Enters the nervous system through the neuromuscular junctions.
• Produces acute inflammation of the brain
• Brain stem encephalitis
•  Coma and death soon follow.

TYPES

 Furious, or encephalitic rabies

• This occurs in 80 percent of human cases.
• The person experience hyperactivity
• Headache, fever, irritability, restlessness and anxiety.
• Dilated pupils
• Muscle pain
• Vomiting
• Salivation
• Hydrophobia
• Phase coninue 
• Coma
• Death

Paralytic or “dumb” rabies

•  Patient experiences depression
• Paralysis followed by a coma. 
• Death eventually results from respiratory arrest.

SYMPTOMS

Five stages

• incubation
• prodrome
• acute neurologic period
• coma
• death

Prodrome

• Early, flu-like symptoms
• Fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or above
• Headache
• Anxiety
• Feeling generally unwell
• Sore throat and a cough
• Nausea and vomiting
• Discomfort at the site of the bite
• Last from 2 to 10 days, and they worsen over time.

Acute neurologic period

• Neurologic symptoms develop
• confusion and aggression
• partial paralysis, involuntary muscle twitching, and rigid neck muscles
• convulsions
• Toward the end of this phase, breathing becomes rapid and inconsistent.
• hyperventilation and difficulty breathing
• hypersalivation
• frothing at the mouth
• Hydrophobia
• Hallucinations, nightmares, and insomnia
• Priapism, or permanent erection, in males
• Photophobia, or a fear of light

Coma and death

• Person enters a coma
• Death will occur within a matter of hours, unless they are attached to a ventilator.
• Rarely, a person may recover at this late stage.

Why does rabies cause a fear of water?

• Rabies used to be known as hydrophobia
• Cause a fear of water.
• Intense spasms in the throat are triggered when trying to swallow.
• Even the thought of swallowing water can cause spasms.
• This is where the fear comes from.

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