Rabies Flashcards
what family/genus is rabies virus
rhabdovirus
genus lyssavirus
structure and target of rabies
enveloped
neurotropic - attacks CNS cells (esp. neurons)
rabies transmission
bite wound
other modes possible but less common (saliva contact with mucous membranes/broken skin, aerosolization, organ transplantation)
rabies pathogenesis
- bite wound
- viral replication in myocytes
- retrograde transport to dorsal root ganglia
- replication in DRG and motor neurons of the spinal cord
- rapid ascent to the brain
- replication in brain neurons causing encephalitis
- centrifugal spread along nerves
- systemic spread
what are the main targets of rabies virus
- brain neurons –> induces behavioral changes to increase biting behavior
- salivary glands –> shedding site, shed in saliva for days to 2 weeks prior to clinical signs
is there a carrier state for rabies
no, all affects animals will die
how does rabies persist since there is no carrier state and it is not environmentally resistant
has slow progression (long incubation period) that allows animals to shed virus for a long time before they die
alters behavior to increase shedding through bite wounds
clinical outcome of rabies
death
all animals die once clinical signs are shown
clinical signs of rabies
- pica
- hypersalivation
- hydrophobia
- numbness/tingling at bite site
- severe neurologic disease
- behavior changes (furious vs paralytic form)
is behavior changes alone diagnostic of rabies
no because there are two presentations and some paralytic forms can progress to furious
furious form
signs of aggression
paralytic form
stupor; animals seem docile
what is the treatment for rabies
none
some human cases have survived by placing in induced coma + antiviral + anti-inflammatories
what are the majority of human rabies cases in the world caused by
dog bites
(canine variant)
what is the most significant factor in reducing the number of human rabies cases in the US
canine rabies vaccination
canine variant has been ELIMINATED from the US
what rabies strain are the majority of cases in the US caused by
bat strains
what are the main reservoirs of rabies in the US
bats
raccoons
skunks
foxes
what are the main reservoirs of rabies in california
bats
skunks
only terrestrial strain in CA: skunks
what animals are susceptible to rabies
all mammals
prevention mechanisms for human rabies
vaccinations for at risk groups only
post-exposure treatment in humans
if not vaccinated: immediate dose of human rabies Ig + rabies vaccine at days 3, 7, and 14
if vaccinated: vaccine booster only
- NO vaccinated animals have ever acquired the disease
prevention mechanisms for animal rabies
vaccinations required for all domestic animals
- dogs and cats: initial vaccine at 12-16 weeks + 1 year booster + annual or q3 year boosters (depending on type)
no vaccine available for wildlife
how is rabies officially diagnosed
DFA of post mortem animal ONLY
- submit whole carcass or head
- do not freeze (takes time to thaw but does not affect sample)
what is seen on DFA with rabies
perivascular cuffing
intracytoplasmic inclusions (negri bodies)
are veterinary diagnostic labs validated for diagnosing rabies for human health purposes
NO - must be health department
post exposure treatment for pets
if unvaccinated: vaccinate animal and quarantine for 4 months without human contact OR euthanasia
if overdue for vaccine: revaccinate + quarantine for 45 days with owner
if vaccinate: revaccinate + quarantine for 45 days with owner
- unlikely to get disease if current on vaccines
handling pet after biting a human
if its a pet: confine for 10 days and observe, do not administer vaccine during observation period
if its a stray or wildlife: euthanize and test regardless of signs
