Rabies
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Introduction
- An acute progressive encephalitis zoonotic disease caused by a bullet-shaped rhabdovirus called rabies virus
- The virus is a single-stranded enveloped RNA virus and has the potential to infect all mammals
- Transmitted by infected secretions, usually saliva
- Infected dogs are responsible for 99% of human rabies infection
- Wildlife -foxes, wolves, jackals, bats, racoons, skunks, or mongoose account for a small proportion of transmission in non-endemic countries
- Infection occurs from scratch and bites or when infected secretions are in direct contact with exposed skin or mucous membranes
- Occasionally contact with a virus-containing aerosol or the ingestion or transplant of infected tissues may initiate the disease process
Clinical features
After an incubation period of 1 to 3 months (sometimes from 1 week to 1 year), infected patients develop:
- Symptoms around site of bite/scratch
- Pain
- Parasthesiae
- A non-specific prodrome of 1 - 4 days consisting of
- Fever
- Headache
- Malaise
- Myalgia
- Anorexia
- Nausea
- Vomiting
- Sore throat
- Cough
- Paraesthesia
- An acute encephalitic stage (presenting as forms of furious or paralytic rabies)
- Furious rabies
- Signs of hyperactivity-agitation, combativeness, restlessness
- Excitable behaviour
- Hallucinations and pyschosis
- Confusion
- Muscle spasms
- Meningismus
- Seizures
- Hydrophobia (fear of water)
- Sometimes aerophobia (fear of drafts or of fresh air).
- Death occurs after a few days due to cardio-respiratory
- Paralytic
- Muscles gradually become paralyzed, starting at the site of the bite or
- A coma slowly develops, and eventually death
- Brainstem dysfunction
- Diplopia
- Facial paralysis
- Optic neuritis
- Difficulty with deglutition
- Priapism
- Spontaneous ejaculation
- Coma
Rabies, once symptomatic is usually fatal
Differential diagnoses
- Gullain-Barre syndrome
- Other causes of viral encephalitis
- Poliomyelitis
- Allergic encephalomyelitis
Diagnoses
- By diagnostic techniques detecting whole viruses, viral antigens, or nucleic acids in infected tissues (brain, skin, or saliva) intra-vitam and postmortem
- Fluorescent antibody testing on brain tissue is the gold standard for rabies diagnosis
Investigations
- Full Blood Count and differentials
- Urea and Electrolytes
- Culture of secretions
- Cerebro Spinal Fluid (C SF) analysis
- Serology
- Pulmonary Chain Reaction (PCR)
- Direct rapid immunohistochemistry tests
- Enzyme-linked immunosorbent assays
Treatment goals
- Disinfect wound; avoid early suturing
- Provide passive immunization with antirabies antiserum
- Provide active immunization with the vaccine
Non-drug treatment
Wound care
The wound or site of exposure should be:
- Cleansed under running water
- Washed for several minutes with soapy water
- Disinfected and dressed simply
It should not be sutured immediately
Drug treatment
Purified cell culture and embryonated egg-based rabies vaccines (CCEEVs) is recommended.
- CCEEVs can be administered by intradermal (ID) or IM injection
- Post-exposure prophylaxis (PEP) and Pre-exposure (PrEP) regimens require a series of vaccine injections according to the manufacturers recommended schedules
- Most vaccine manufacturers currently recommend:
- for PrEP a 1-site IM 3-dose regimen and
- for PEP a 1-site IM 5-dose regimen on days 0, 3, 7, 14 and 28 or
- 4-dose Zagreb regimen (2-site IM on day 0 and 1-site IM on days 7 and 21).
Schedules
- Unimmunized persons or those whose prophylaxis is probably incomplete.
- Rabies (purified cell culture) vaccine:
- Adult: 1 ml by deep subcutaneous or intramuscular injection in the deltoid region on days 0, 3, 7, 14 and 28
Plus:
- Rabies immunoglobulin (RIG) given on day 0
- Maximum dose calculation for RIG is 40 IU/kg body weight for equine derived RIG (eRIG), and 20 IU/kg body weight for human derived RIG (hRIG).
- Child: same as for Adult
- For fully immunized persons:
- Rabies (purified cell culture) vaccine
- Adult: 1 ml by deep subcutaneous or intramuscular injection in the deltoid region on days 1 and 3
- Child: same as for adult
Post-exposure prophylaxis (PEP)
- Should be initiated as soon as possible after exposure
- The decision to initiate PEP should be based on contact categories below:
|
Categories of contact with suspect rabid animal |
Description |
PEP |
|
Category I |
Touching or feeding animals, animal licks on intact skin (no exposure) |
Washing of exposed skin surfaces, no PEP |
|
Category II |
Nibbling of uncovered skin, minor scratches, or abrasions without bleeding (exposure) |
Wound and immediate vaccination |
|
Category III |
Single or multiple transdermal bites or scratches, contamination of mucous membrane or broken skin with saliva from animal licks, exposures due to direct contact with bats (severe exposure) |
Wound washing, immediate vaccination, and administration of rabies immunoglobulin |
- Pregnancy not a contraindication to rabies vaccine
Supportive measures
- Allay anxiety: reassure
- Other measures as appropriate for clinical situation
Prevention
Pre-exposure prophylaxis
Should be offered to persons at high risk of exposure and/or contact with rabies virus:
- Veterinarians
- Cave explorers
- Laboratory workers who handle the rabies virus
- Animal handlers
- Workers in quarantine stations
- Field workers who are likely to be bitten by infected wild animals
- Certain port officials Bat handlers
- Persons living in (or traveling to) areas where rabies is enzootic and/or where there is limited access to prompt medical care.
- Those caring for patients caring for patients with rabies (Although there is no proven evidence of human transmission)
- If there is substantial risk of exposure, and rapid access to post-exposure prophylaxis is limited, give pre-exposure prophylaxis Rabies vaccine
PrEP schedule
- 2-site ID vaccine administered on days 0 and 7
Or
- 1-site IM vaccine administration on days 0 and (1 ml by deep subcutaneous or intramuscular injection in the deltoid region)
Booster doses every 2 - 3 years for those at continued risk