Lecture 33 11/14/24

Question 1

What are the characteristics of rabies virus?

Answer 1

-RNA virus
-susceptible to disinfectants
-inactivated by drying
-genetic variants are host-adapted with high antigenicity
-only causes disease in mammals

Question 2

What are the characteristics of rabies virus host adaptations?

Answer 2

-distinct variants associated with specific hosts
-geographically definable regions
-transmission between members of the same species
spillover infections possible but not sustainable
-variants can switch to new hosts
-globally carried by dogs

Question 3

What are the characteristics of rabies globally?

Answer 3

-neglected zoonosis
-95% of cases occur in Asia and Africa
-responsible for 40% of deaths in children under the age of 15 in underdeveloped countries
-threat to billions of people with limited access to rabies post-exposure prophylaxis

Question 4

What are the characteristics of rabies in the US?

Answer 4

-reservoirs include terrestrial carnivores and bats
-pets and livestock are infected by wildlife
-humans are exposed by livestock, unvaccinated pets, and bats

Question 5

What are the characteristics of rabies prevalence in the US?

Answer 5

-true prevalence is unknown
-cases are reported to local and state departments and the CDC
-reportable disease on both state and federal level

Question 6

What has lead to a decline in rabies cases in the US?

Answer 6

-vaccination
-leash laws
-removal of stray animals

Question 7

How are rabies cases lost to the reporting system?

Answer 7

-not observed
-not suspected of being rabid
-not captured
-not sent to diagnostic lab
-not suitable for testing
-falsely diagnosed negative

Question 8

What are the characteristics of rabies variants in the US?

Answer 8

-7 antigenic variants
-each variant has distinct geographic region
-each region has a single reservoir species
-1% of bats in wild are estimated to have rabies (throughout US)

Question 9

What percent of confirmed rabid animals are wild?

Answer 9

around 91%

Question 10

Why is the raccoon rabies variant problematic?

Answer 10

-raccoons thrive in suburban/urban settings
-aggressive and swift animals
-increase in human exposures, need for PEP risk assessment, and animal control calls

Question 11

What are the characteristics of rabies in rodents and lagomorphs?

Answer 11

-species are susceptible, but cases are rare
-no role in epidemiology/dead end hosts
-no human cases associated with exposure

Question 12

What are the characteristics of rabies in TN?

Answer 12

-last human case in 2002
-seen in bats, skunks, and raccoons

Question 13

Which animals are evaluated under “enhanced” surveillance practices for raccoon rabies in East TN?

Answer 13

-roadkill
-nuisance animals

Question 14

How is rabies most commonly transmitted?

Answer 14

saliva containing the virus is spread through a bite

Question 15

What are the characteristics of bats spreading rabies?

Answer 15

-can transmit rabies even when other terrestrial reservoirs are not present
-often dwell in houses
-active at night
-very small teeth; bites not always noticed

Question 16

What can lead to a rabies exposure not resulting in disease?

Answer 16

-no virus in saliva
-virus not multiplying/progressing to CNS
-protective antibody response

Question 17

How does rabies cause disease?

Answer 17

-virus enters peripheral nerves
-virus enters CNS through retrograde axoplasmic flow
-virus rapidly spreads through CNS and causes encephalitis
-virus spreads to salivary glands from CNS
-neurologic and behavioral signs result

Question 18

What is the period of communicability?

Answer 18

period of time during which a rabid animal is shedding virus in the saliva and therefore is capable of transmitting virus to a susceptible host

Question 19

How long is the period of communicability in dogs, cats, and ferrets?

Answer 19

up to 3 days prior to clinical signs until death

Question 20

Why is a 10 day quarantine used for dogs, cats, and ferrets that bite people?

Answer 20

because shedding only begins up to 3 days prior to clinical signs, animals capable of shedding rabies should begin experiencing clinical signs within the quarantine if they are capable of spreading rabies to the bite victim

Question 21

Why are animals that bite that are overdue for rabies vx not vaccinated until after the 10 day quarantine?

Answer 21

to make sure vx reactions are not mistaken for clinical signs of rabies

Question 22

What is the incubation period?

Answer 22

period of time from infection until onset of clinical signs of disease

Question 23

What can affect the length of the rabies incubation period?

Answer 23

-amount of inoculum
-nerve supply at site
-distance to CNS
-host resistance
-strain of virus

Question 24

What are the characteristics of human rabies cases in the US?

Answer 24

-1 to 5 cases annually
-70% males
-average age around 46 years old

Question 25

What contributes to human deaths from rabies worldwide?

Answer 25

-prevalence is high in rural, underdeveloped areas
-cost of post-exposure prophy. is too high for developing countries