Togaviridae Flashcards
Which of the following is NOT true of Togaviruses?
A. Positive-sense, linear, single-stranded RNA viruses
B. They are Arboviruses that of zoonotic importance.
C. The family consists of 2 important Genera: Alphavirus and Rubivirus
D. All of the above are true.
B.
Only the genus Alphavirus contains viruses that are considered Arboviruses (viruses borne by arthropod vector); Rubiviruses such as German measles in humans, are not transmitted by arthopods.
T or F:
For Eastern Equine Encephalitis Virus, there are at least 4 known lineages, with lineage I being in North America, Canada and the Caribbean and the most virulent to humans and horses, and lineages II and III being in Central and South America and being less virulent.
True
Which of the following is an INCORRECT association for the ENZOOTIC cycle for EEEV?
A. This cycle happens generally in the summertime
B. The reservoir host here is the passerine bird
C. The vector here is the Aedes or Coquilettidia mosquito
D. Rodents and reptiles can also be reservoirs
E. Passerine birds develop sufficient viremia to infect enzootic vectors as well as bridge vectors, therefore also serving as an amplifying host
C. Is incorrect. The ENZOOTIC VECTOR=Culiseta melanura
The EPIZOOTIC vector is Aedes and some other mosquitoes
T/F:
In the EEEV transmission cycle, humans and horses serve as dead-end hosts, as well as caged pheasants.
False
Caged pheasants CAN transmit the virus to each other via pecking or eating each other; therefore they develop a viremia sufficient to transmit the disease…thus they are not dead-end hosts.
Which of the following is NOT a clinical sign of EEEV in horses?
A. Fever, anorexia, depression B. Hypersensitivity to light C. Periods of colic before neurological signs D. Head pressing E. Complete paralysis
B.
Sensitivity to SOUND
T/ F:
EEEV in humans can manifest in either an encephalitic form, where patients display cyanosis and then seizures and coma, or a systemic form, in which no neurological symptoms occur but patients exhibit muscle and joint pain. The disease has about a 30% case mortality rate.
True.
Also, people get fever, malaise, vomiting, diarrhea and anorexia before neurological symptoms arise.
T/F:
Western Equine Encephalitis (WEEV) seems to have emerged via a recombination event of an EEEV-like virus and a Sindbus-like Alphavirus.
True.
Remember, recombination is (along with reassortment) an example of genetic shift, which is a sudden change, as opposed to genetic drift, which is a cumulation of mutations over time.
The following is true of WEEV, EXCEPT:
A. It appears to be less virulent than EEEV
B. It is prevalent in the Western half of North and South Americas
C. The enzootic forms in South America are more virulent than the epizootic forms in N. America
D. Just as in EEEV, the Aedes mosquito is the main epizootic vector
C. The epizootic forms in NA are more virulent than the enzootic forms seen in SA
What is the ENZOOTIC vector for EEEV?
A. Aedes spp
B. Culex tarsalis
C. Passerine birds
D. Lagomorphs and rodents
B. The specific vector mentioned for the ENZOOTIC cycle for WEEV is Culex tarsalis (although the figure implies it could be any Culex spp)
Aedes spp serve as the EPIZOOTIC vector
Passerine birds are the endemic reservoirs as well as epizootic amplifying hosts
Lagomorphs and rodents can serve as amplifying hosts in the epizootic cycle
T/F:
For WEEV, prairie dogs and jackrabbits serve as primary amplifying hosts, whereas house finches and sparrows are known to serve as secondary amplifying hosts.
False
Sparrows/finches= Primary amplifying hosts
Jackrabbits/prairie dogs=secondary amplifying hosts
T/F:
For Venezuelan Equine Encephalitis Virus (VEEV), there are 6 antigenic subtypes, with 1A-1C being the most virulent for horses and existing predominantly in the epizootic cycle, and are generally referred to as epizootic strains.
True.
The enzootic strains are 1D-1F and II-IV
and are less virulent
What are the correct enzootic cycle primary vectors, reservoirs, and bridge vectors for VEEV, respectively?
A. Culex Melanconium, Aedes and Posorophora, cotton or spiny rats
B. Culex Melanconium, Cotton or spiny rats, Aedes and Posophora
C. Aedes or Posophora, Cotton/spiny rats, Culex Melancomum
B.
T/F:
For the epizootic cycle of VEEV, the horse serves as the amplifying host and several species of mosquitoes serve as primary vectors.
True
T/F:
In VEEV, endemic strains can mutate to form epidemic strain 1AB.
True.
A major concern/distinction with VEEV compared to the other Alphaviruses is:
A. Devastating encephalitis caused to humans and horses which spreads fast
B. In-utero infections in horses
C. Abortion, stillbirth, fetal encephalitis and congenital disease in humans
D. Babies and young children are especially vulnerable to the neurological effects of this disease.
E. All except A
E.
