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
