Rabies

Question 1

what family/genus is rabies virus

Answer 1

rhabdovirus
genus lyssavirus

Question 2

structure and target of rabies

Answer 2

enveloped

neurotropic - attacks CNS cells (esp. neurons)

Question 3

rabies transmission

Answer 3

bite wound

other modes possible but less common (saliva contact with mucous membranes/broken skin, aerosolization, organ transplantation)

Question 4

rabies pathogenesis

Answer 4

1. bite wound
2. viral replication in myocytes
3. retrograde transport to dorsal root ganglia
4. replication in DRG and motor neurons of the spinal cord
5. rapid ascent to the brain
6. replication in brain neurons causing encephalitis
7. centrifugal spread along nerves
8. systemic spread

Question 5

what are the main targets of rabies virus

Answer 5

1. brain neurons –> induces behavioral changes to increase biting behavior
2. salivary glands –> shedding site, shed in saliva for days to 2 weeks prior to clinical signs

Question 6

is there a carrier state for rabies

Answer 6

no, all affects animals will die

Question 7

how does rabies persist since there is no carrier state and it is not environmentally resistant

Answer 7

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

Question 8

clinical outcome of rabies

Answer 8

death

all animals die once clinical signs are shown

Question 9

clinical signs of rabies

Answer 9

• pica
• hypersalivation
• hydrophobia
• numbness/tingling at bite site
• severe neurologic disease
• behavior changes (furious vs paralytic form)

Question 10

is behavior changes alone diagnostic of rabies

Answer 10

no because there are two presentations and some paralytic forms can progress to furious

Question 10

furious form

Answer 10

signs of aggression

Question 11

paralytic form

Answer 11

stupor; animals seem docile

Question 12

what is the treatment for rabies

Answer 12

none

some human cases have survived by placing in induced coma + antiviral + anti-inflammatories

Question 13

what are the majority of human rabies cases in the world caused by

Answer 13

dog bites
(canine variant)

Question 14

what is the most significant factor in reducing the number of human rabies cases in the US

Answer 14

canine rabies vaccination

canine variant has been ELIMINATED from the US

Question 15

what rabies strain are the majority of cases in the US caused by

Answer 15

bat strains

Question 16

what are the main reservoirs of rabies in the US

Answer 16

bats
raccoons
skunks
foxes

Question 17

what are the main reservoirs of rabies in california

Answer 17

bats
skunks

only terrestrial strain in CA: skunks

Question 18

what animals are susceptible to rabies

Answer 18

all mammals

Question 19

prevention mechanisms for human rabies

Answer 19

vaccinations for at risk groups only

Question 20

post-exposure treatment in humans

Answer 20

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

Question 21

prevention mechanisms for animal rabies

Answer 21

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

Question 22

how is rabies officially diagnosed

Answer 22

DFA of post mortem animal ONLY
- submit whole carcass or head
- do not freeze (takes time to thaw but does not affect sample)

Question 23

what is seen on DFA with rabies

Answer 23

perivascular cuffing
intracytoplasmic inclusions (negri bodies)

Question 24

are veterinary diagnostic labs validated for diagnosing rabies for human health purposes

Answer 24

NO - must be health department

Question 25

post exposure treatment for pets

Answer 25

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

Question 26

handling pet after biting a human

Answer 26

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