Togaviridae

Question 1

Where do Togaviruses replicate within the cell?

Answer 1

cytoplasm

Question 2

What are bridge vectors?

Answer 2

Vectors that can interchange between ruban, sylvatic, and or rural life cycles

Question 3

Eastern equine encephalitic (EEV) belongs to what genus?

Answer 3

Alphavirus

**ZOONOTIC

Question 4

How many distinct linages of EEV are there?

Answer 4

4. I, IIA, IIIB, III

I - is the most pathogenic

Question 5

What mosquito is the most common vector of EEV?

Answer 5

Culleta melanura

Question 6

Who is involved in the Primary (enzootic) cycle of EEV? When does it occur?

Answer 6

Enzootic EEV cycle occurs in the summer between:

Marsh bird (amplifying host) and Mosquitos (Cullseta melanura)
(sometimes rodents and reptiles can be reservoirs)

Question 7

Who is involved in the Epizootic cycle of EEV?

Answer 7

Wild and Marsh birds and Aedes spp of Mosquito

Humans and Horses are DEAD END HOSTS

Question 8

What is the progression of EEV after getting infected via mosquito bite?

Answer 8

Replication in nyoblasts, fibroblasts, LN, Osteoblasts, lymphoid tissue –> Replication in organs –> Viremia –>CNS–> replication in neurons, vascular endothelium, glial cells –> apoptosis of neurons/glial cells –> encephalomyelitis

Question 9

What clinical signs are seen in a horse with EEV?

Answer 9

Fever, anorexia, depression
hemorrhage in brain, CNS signs, paralysis, head pressing

*many horses only suffer mild dz

Question 10

What clinical signs are seen in birds with EEV?

Answer 10

Typically none, as they are the reservoir, occasionally: depression, tremors, paralysis, necrosis of spleen and liver

Question 11

Where is the Western Equine Encephalitis virus (WEEV) the most virulent?

Answer 11

In North American - strains are more virulent

Question 12

T/F: WEEV caused more severe dz than EEV

Answer 12

FALSE

WesternEEV is less severe than EEV

Question 13

Who is involved in the PRIMARY (enzootic) cycle of WEEV?

Answer 13

Birds are the amplifying hosts
Culex spp of mosquito are the vector

Horse and human are dead end hosts

Question 14

Who is involved in the SECONDARY (epizootic) cycle of WEEV?

Answer 14

Rodents are the amplifying hosts
Aedes spp of Mosquito are the vector

Horses and humans are dead end hosts

Question 15

T/F: WEEV is clinically indistinguishable from EEV

Answer 15

TRUE

clinical signs are very similar (although WEEV infections tend to be more mild)

Question 16

Mortality rate of horses with WEEV is up to ___%?

Answer 16

30%

Question 17

What clinical signs may you see in birds with WEEV

Answer 17

Decrease in egg production (turkeys), Neuro signs (Emu)

Question 18

What subtypes of Venezuela Equine Encephalitis (VEEV) are the most virulent?

Answer 18

1A, 1B, 1C = epizootic, highly virulent for horses

the remaining groups are not virulent to horses

Question 19

Who is involved in the enzootic cycle of VEEV?

Answer 19

Rodents = amplification reservoir
Culex spp of mosquito is the vector

Humans and horses are dead end hosts

Question 20

Who is involved in the epizootic cycle of VEEV?

Answer 20

***Horses = amplifying hosts
Mosquitos = vectors

Humans = dead end host

Question 21

T/F: Mutations can occur in the less virulent strains of VEEV (strains 2-6) that can convert them to high virulent strains

Answer 21

TRUE

Question 22

How do you control VEEV?

Answer 22

Mosquito control - chemical or biological and surveillance

Question 23

T/F: there is a combo vaccine that covers VEEV, EEV, and WEEV

Answer 23

FALSE

Combo vax for EEV and WEEV
VEEV has its own live vax (uses TC83 to make it)