Rabies Flashcards
Rabies - virology
Neurotropic virus - single strand negative send RNA virus
-Part of Lyssa genus
-5 proteins
-bullet shaped
-Genotype 1 = classic rabies virus [source = terrestrial mammals]
Rabies - transmission
Saliva of infected animals
Infection via broken skin
Rabies - pathogenesis
Virus neters nerve endings - virus evades immune surveillance
Centripetal retrograde axonal transport to brain
Trans-synpatic spread
Viral replication in CNS
Inclusion [Negri] body formation
Neurons intact - but dysfunctional
Centrifugal neurongal transport to:
-Salivary glands - for viral excretion
-Virus carried to skin, heart, muscle, tongue
Rabies - incubation period
Days to years - usually 20-90 days
Rabies - yearly cases
59,000 cases/year
Children <15 years 40%
Rabies - country with largest burden
India
36% of global rabies
Rabies - common prodromal stage
Virus in PNS - reaching dorsal root ganglion = causing paraesthesia and intense pruritus
Rabies - furious rabies [80% cases] clinical features
Brainstem, cranial nerves, limbic system
Phases of arousal and lucid intervals
CN lesions III [oculomotor], VII [facial] and VIII [vestibulocochlear]
Autonomic stimulations:
-Secretions, hypersalivation, hyperthermia, priapism
Cardiac arrhythmias
Coma
Paralysis
Hydrophobia:
-Worsens as disease progresses
-Reflex forceful jerky inspiratory muscle spasms with inexplicable terror
Survival <7 days following onset of clinical symptoms
Rabies - Paralytic/’dumb’ rabies clinical features
More insidious
Medulla, spinal cord, spinal nerves
Ascending paralysis - loss of tendon reflexes
Fasciluations
Fever, sweating
Bulbar/respiratory paralysis
Hydrophobia
Survival <30 days
Rabies - complications
Heart:
-Arrythmias, hypotension, cardiac failure
Lungs:
-Asphyxiation, pneumonia, inspiratory spasms, ARDS
CNS:
-Convulsions, hypo/hyperpyrexia, DI, SIADH
GI:
-Bleedings, stress ulceration
Rabies - diagnosis
Skin punch biopsy - back of neck with hair follicles:
-Immunofluorescence - rabies antigen in hair follicle, PCR
Saliva serial collection = PCR
Serum, CSF = neutralising antibody
Most are post-mortem:
-Brain-needle necropsy
Rabies - pathology
Negri body - eosinophilic inclusion body in nerve cell
Rabies - treatment
Rabies 100% fatal in symptomatic unvaccinated patients infected by dogs = palliation
Attempt ICU only if:
-American bat virus
-Some vaccine was given before onset
-Early appearance of antibody
-ICU facilities available
Rabies - immediate management of wound/dog bite
Scrub with soap and water for 15 mins
Virucidal agents - povidine iodine, 70% ethanol = flood wound
Avoid suturing
Remember tetanus
Risk assessment:
-Skin intact
-Contamination
-Species of mammal
-Vaccination history
-Behaviour and appearance of animal [if dog behaving normally 15 days following bite = unlikely dog is rabid]
Rabies - post-exposure management
IM rabies post-exposure vaccine [Essen] regimen = day 0, 3, 7 and between 14-21 [for unvaccinated]
If previously vaccinated = day 0 + 3 IM or 4 sites intradermal day 0
[IM only for immunocompromised = 5 doses]
Rabies immunoglobulin [RIG]/passive immunisation
-Used for category 3 exposure
-For immunosuppressed patients [regardless of vaccination status]
-Locally infiltrated into wounds
-Covers first 7 days while antibodies against vaccine is raised
Rabies - category 3 HIGH risk
Transdermal bites or scratches
Licks on broken skin
Mucous membrane saliva contact
Exposure to bats or raw meat of rabid animal
Immunocompromised people
Deep multiple bits to head, neck, hands
Rabies - vaccine SE
Local symptoms - irritation site of infection
Generalised symptoms [14%]:
HA, fever, malaise
Systemic allergic reaction <6%:
-Rash, angioedema, arthralia
Anaphylaxis = extremely rare
