Rabies
It is endemic throughout the world.
The fatality is almost 100 %.
Reservoirs
- In Europe- Foxes, dogs, cats, cattle and horses
- In Asia and
- In Central and
Infection in animals causes death in 2 weeks. Infected animals change behaviour to either becoming aggressive or familiar.
Transmission is through animal bite or contact with infectious body fluids. Copies salivation that occurs in infected animal as part of the clinical presentation is an important of infectious material.
Aerosol transmission is rare however transmission in laboratories and in caves which harbour rabid bats has been reported.
Transmission in corneal transplanted patient has been documented in literature.
Infectious period for infected animals is 5 days before the onset of illness to the time the animal dies.
Incubation period in human range between 2 to 8 weeks depending on the distance from the head. However it could be as long as 6-9 months.
Clinical
Presentation
The illness has insidious onset.
There may be history of animal bite. Paresthesia around the bitten are should raise suspicion.
Fever, headache, nausea and sense of apprehension are the early signs.
Spasm in response to tactile, auditory, visual or olfactory stimuli is common and the patient should be kept in quite and dark room.
Later the patient develops hydrophobia and hallucination.
Paralysis will be followed by coma.
Ascending flaccid paralysis with sphincter involvement and sensory disturbance is observed in the later stage.
Respiratory and bulbar paralyses are the main causes of death.
Investigation
Quarantine the animal.
Tests
Testing is carried out in containment level 2 or 3.
Fluorescent antibody testing of corneal impression (not scraping) or skin biopsies from the nuchal area of the neck with hair follicle containing peripheral nerve is good method of testing for rabies. Negative results does not exclude rabies.
The virus can be isolated from saliva, CSF and other body fluids.
RT-PCR can be done on saliva and other tissues.
Serology- rabies antibodies may be detected on the blood and CSF.
Post-mortem brain tissues can be stained with fluorescent antibody.
Management
Care of Exposed
person
Patient should be assessed for
Exposure- bitten or licked on
the open wound or mucous membranes,
The site,
The time and place of the
incident,
The animal species and whether
it is under observation or not, and
Information on vaccination
history of the animal and the patient
Risk assessment
and action
Level of Risk Action
No risk No PEP
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Low risk Not immunised 5 doses at 0,3, 7, 14, and 30 days
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Completed Give further
Pre-exposure 2 doses at 0 and 3 or 7 days
Vaccine
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High risk Not immunised 5 doses at 0, 3, 7, 14 and 30 days and *Immunoglobulin
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Completed Give further
Pre-exposure 2 doses at 0 and 3 or 7 days.
Vaccine
* Rabies specific human immunoglobulin- 20 IU/kg. Half given around the wound after cleaning, and the rest given intramuscular. The main adverse effect is pain around the injection area.
Post-exposure prophylaxis
Fully vaccinated individual requires only 2 booster doses of vaccine.
Not fully vaccinated or unvaccinated individual requires 5 doses of vaccine. Depending on the risk the individual may require rabies specific human immunoglobulin.
Care of symptomatic patient
Treatment is ineffective.
Patient should be isolated.
Sedation may alleviate pain. Recently a patient has recovered from Rabies after she was induced to have coma for several weeks. The expert opinion is that it is not the direct cytopathic effects that cause fatality in patients but it is the autonomic nervous system crises.
Strict infection control measure should be implemented to reduce transmission of infection to staff members.
The staff should be vaccinated with 4 intradermal injections of 0.1 ml given on to the four limbs.
Protective clothing such as gloves, gowns and face visors should be used to reduce contact with body fluid. Staff exposed to secretions to the mucous or broken skin should start PEP.
Prevention
In western European Countries, vaccination of wild animal has been successful in controlling Rabies transmission in wild animal.
Pre-exposure prophylaxis
Three doses at 0, 7 and 28 days provide adequate protection. Each dose is injected to deep subcutaneous tissue or intramuscularly.
Single booster dose at 2 to 3 years interval should be given if there is continuous exposure.
For travellers – 2 doses is enough at 0 and 4 weeks. The response rate after 2 dose is over 98 %.