Rabies is a viral disease spread to humans through bites or scratches from infected animals like dogs. It causes inflammation of the brain and is fatal without treatment. The rabies virus travels through the nervous system from the site of infection to the brain. Symptoms in humans include fear of water, increased reflexes, and mental changes. Post-exposure prophylaxis includes wound cleansing, vaccine administration, and other measures to prevent the virus from reaching the nervous system. Pre-exposure prophylaxis through vaccination is recommended for those at high risk of exposure like animal handlers.
3. • Rabies is a viral disease that cause Encephalitis in warm
blooded animals , it is also known as Hydrophobia
• Its caused by Lyssavirus type 1 ( family – Rhabdoviridae )
• Transmission of Rabies to human :- Bites ( 95%) ,
scratches & licks from infected animals
• It is a zoonotic disease of warm blooded animals such as –
Dogs , cats , bats , wolves etc.
• Rabies is described the disease in 2300 B.C , The word “
“Rabies” originates from “rabhas” meaning “to do violence”
it comes from Indian ancient Sanskrit dating 3000 B.C
• Because there is no cure ( in ancient ) those that had bitten
by a rabid dog would commonly commit suicide to avoid
painful death.
• Louis Pasteur was the first person to diagnose that rabies
targets the CNS and in 1890 created the rabies vaccine.
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• Rhabdovirus
• Lyssavirus Type 1
• Bullet shaped virus
• Size is 180 x 75 nm
• Has a lipoprotein envelope
• Knob like spikes or glycoprotein G
• Matrix protein layer
• Genome – unsegmented , linear ,
neagative sense RNA
5. Host Factors
• All warm blooded animals including man are
susceptible to Rabies.
• Rabies in man is dead-end-infection
• Laborattory staffs working with rabies virus ,
veteranians , dog handlers , and hunters ( face
bigger risk of rabies ).
Mode of Transmission
• Animal Bite : People are infected following a deep
bite or scratch by an infected animals. Dogs are
the main host and transmitter of rabies.
• Licks : licks on broken skin and mucosa can
transmit the disease.
• Aerosol : by inhalation of aerosol infected with
virus –
in lab – lab workers can become infected
in caves – where rabid bats are present.
• Person to person ( rare ) – Human to human
trasnmission is possible through corneal grafting
because rabies antigen has been detected in
corneal cells of a case of Hydrophobia.
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6. • Rabies virus replicates in muscle or connective
tissue cells at or near the site of introduction before it
attaches to nerve endings and enter peripheral
nerves.
• It spreads from the site of infection centripetally via
the peripheral nerves towards the central nervous
system ( 3mm/hr ).
• Following infection of the central nervous system, the
virus spreads centrifugally in peripheral nerves to
many tissues , including salivary gland.
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• The incubation period in man is highly variable ,
commonly 1-3 months following exposure but may
vary from 7 days to many years.
• The Incubation period depends on the:
• Site of bite
• Severity of the bite
• Numbers of wounds
• Amount of virus injected
• Species of biting animal
• Protection provided by the clothing and treatment
undertaken if , any.
• In general , incubation period tends to be shorter in
severe exposure and bites on face , head , neck and
upper extremeties and bites by wild animals.
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• Rabies in man is called Hydrophobia
• Prodromal stage – the disease begins with
prodromal symptoms such as headache ,
malaise , myalgia , sore throat and slight fever
lasting for 3-4 days.
• There is pain and tingling or numbness at the
site of bite.
• Acute neurologic stage – widespread excitation
and stimulation of all parts of nervous system
usually involving in order the sensory system
motor system , sympathetic system and mental
system.
• The patient is intolerant to noise , bright light or a
cold draught of air ( sensory ), Aerophobia ( fear
of air ) may be present.
• Increases reflexes and muscle spasm.
• Dilation of pupil , increased perspiration ,
saliavation and lacrimation.
• Mental changes include fear of death , anger ,
irritability and depression
• Swallowing liquid become unsuccessful.
• This characteristic symptom of hydrophobia (fear
of water) is pathognomonic of rabies and is absent
in animals.
• The duration of illness is 2 to 3 days, but may be
prolonged to 5-6 days in exceptional cases.
• Patient dies abruptly due to respiratory arrest ,
convulsion or pass to coma and paralysis.
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Diagnosis
• A clinical diagnosis of hydrophobia can be made on
the basis of history of bite by a rabid animal and
characteristic signs and symptoms.
• Laboratory diagnosis- The lab tests not routinely
done for the management of animal bite cases as
these are not cost effective and have limited
availability in specific centres of big cities.
• Rabies can be confirmed in patients early in the
illness by antigen detection using
immunofluorescence of skin biopsy, and by virus
isolation from saliva and other secretions.
Treatment
• There is no specific treatment for rabies. Case
management includes the following procedure :
• The patient should be isolated in a quiet room
protected as far as possible from external stimuli
such as bright light, noise or cold draughts which
may precipitate spasms or convulsions.
• Relieve anxiety and pain by liberal use of sedatives.
• Ensure hydration and diuresis
• Intensive therapy in the form of respiratory and
cardiac support may be given.
• Patients with rabies are potentially infectious
because the virus may be present in the saliva,
vomits, tears, urine or other body fluids.
• Where human cases of rabies are encountered
frequently preexposure prophylaxis is
recommended.
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• This may be considered under 2 heads.
• Post-exposure prophylaxis.
• Pre-exposure prophylaxis.
• POST – EXPOSURE PROPHYLAXIS
• The aim of post-exposure prophylaxis is to neutralize the inoculated virus before it can enter the nervous
system.
• Local treatment of wound: The purpose of local treatment is to remove as much virus as possible from the site
of inoculation before it can be absorbed on nerve endings.
• The local treatment comprises the following measures:
• Cleansing : Immediate flushing and washing the wound(s), scratches and the adjoining areas with plenty of
soap and water, preferably under a running tap, for at least 15 minutes
• If soap is not available, simple flushing of the wounds with plenty of water should be done as first-aid.
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• Chemical treatment : residual virus should be inactivated by irrigation with virucidal agents either alcohol (400-
700 ml/litre OR povidone iodine (Betadine).
• Antibiotics and anti-tetanus measure: The application of antibiotics and anti tetanus procedures when
indicated should follow the local treatment recommended above. The use of any local applicant or irritant like
turmeric, red chilli, lime etc. should be discouraged and avoided.
• Intramuscular administration of vaccine for post-exposure prophylaxis:
• The post-exposure vaccination schedule is based on injecting 1 ml or 0.5 ml (the volume depends on the type of
vaccine) into the deltoid muscle (or anterolateral thigh in children aged <2 years ).
• Pre exposure prophylaxis:
• PEP is recommended for anyone who is at continual, frequent or increased risk of exposure to the rabies virus
for example laboratory worker dealing with rabies virus, animal handlers, veterinarians.
• Schedule: i/m 0.5 or 1 ml or i/d administration of 0.1 ml volume per site given on days 0,7,21 or 28.
• Adverse events following immunization:
• Minor and transient erythema, pain and/or swelling may occur at the site of injection
• Mild systemic adverse events following immunization (AEFI), such as transient fever, headache, dizziness and
gastrointestinal symptoms, have been observed in 5-15% of vaccines.
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• .Nerve tissue vaccine :These are prepared
from the animal tissues. These are of the
following types:
• BPL- Vaccine ( Semple vaccine)
• Suckling mouse brain vaccine
• Duck embryo vaccine- Vaxirab
• Cell culture vaccines (currently used)
• Human diploid cell vaccine (HDCV)- Ravivax
• Purified chick embryo cell vaccine (PCECV)-
Rabipur
• Purified vero-cell rabies vaccine (PVRV)-
Abhayrab
The vaccine against rabies are grouped
into three group as follows:
