Lecture 33 11/14/24 Flashcards
What are the characteristics of rabies virus?
-RNA virus
-susceptible to disinfectants
-inactivated by drying
-genetic variants are host-adapted with high antigenicity
-only causes disease in mammals
What are the characteristics of rabies virus host adaptations?
-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
What are the characteristics of rabies globally?
-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
What are the characteristics of rabies in the US?
-reservoirs include terrestrial carnivores and bats
-pets and livestock are infected by wildlife
-humans are exposed by livestock, unvaccinated pets, and bats
What are the characteristics of rabies prevalence in the US?
-true prevalence is unknown
-cases are reported to local and state departments and the CDC
-reportable disease on both state and federal level
What has lead to a decline in rabies cases in the US?
-vaccination
-leash laws
-removal of stray animals
How are rabies cases lost to the reporting system?
-not observed
-not suspected of being rabid
-not captured
-not sent to diagnostic lab
-not suitable for testing
-falsely diagnosed negative
What are the characteristics of rabies variants in the US?
-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)
What percent of confirmed rabid animals are wild?
around 91%
Why is the raccoon rabies variant problematic?
-raccoons thrive in suburban/urban settings
-aggressive and swift animals
-increase in human exposures, need for PEP risk assessment, and animal control calls
What are the characteristics of rabies in rodents and lagomorphs?
-species are susceptible, but cases are rare
-no role in epidemiology/dead end hosts
-no human cases associated with exposure
What are the characteristics of rabies in TN?
-last human case in 2002
-seen in bats, skunks, and raccoons
Which animals are evaluated under “enhanced” surveillance practices for raccoon rabies in East TN?
-roadkill
-nuisance animals
How is rabies most commonly transmitted?
saliva containing the virus is spread through a bite
What are the characteristics of bats spreading rabies?
-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
What can lead to a rabies exposure not resulting in disease?
-no virus in saliva
-virus not multiplying/progressing to CNS
-protective antibody response
How does rabies cause disease?
-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
What is the period of communicability?
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
How long is the period of communicability in dogs, cats, and ferrets?
up to 3 days prior to clinical signs until death
Why is a 10 day quarantine used for dogs, cats, and ferrets that bite people?
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
Why are animals that bite that are overdue for rabies vx not vaccinated until after the 10 day quarantine?
to make sure vx reactions are not mistaken for clinical signs of rabies
What is the incubation period?
period of time from infection until onset of clinical signs of disease
What can affect the length of the rabies incubation period?
-amount of inoculum
-nerve supply at site
-distance to CNS
-host resistance
-strain of virus
What are the characteristics of human rabies cases in the US?
-1 to 5 cases annually
-70% males
-average age around 46 years old
What contributes to human deaths from rabies worldwide?
-prevalence is high in rural, underdeveloped areas
-cost of post-exposure prophy. is too high for developing countries
