Arteriviridae

Question 1

Describe the virions and genome of family Arteriviridae

Answer 1

Enveloped, spherical
Linear, positive-sense, single stranded RNA
*Genomic RNA is infectious

Question 2

T or F: Family Arteriviridae frequently establishes persistent infections

Answer 2

True!

Question 3

Where does Arteriviridae replication take place?

Answer 3

Cytoplasm!
Virions are formed by budding into ER (enveloped, duh)
Released via exocytosis

Question 4

To which genus does equine viral arteritis belong?

Answer 4

Genus arterivirus

One serotype only!

Question 5

Where can equine viral arteritis be found?

Answer 5

Most countries in equines

Question 6

How is equine viral arteritis transmitted?

Answer 6

Spread by carrier stalion (reservoir) 
Lateral spread (masturbation, fomites, personnel) or venereal transmission (natural breeding, artificial breeding) or horizontal (aerosol/respiratory***, fomites, personnel)

Question 7

If transplacental transmission of EAV to the fetus occurs in late gestation, what may result?

Answer 7

A foal with congenitally acquired EAV infection

Question 8

What are the primary sites of virus replication of EVA?

Answer 8

Macrophages and endothelial cells

Damage to blood vessels/endothelium leads to generalized edema and hemorrhages

Question 9

What are secondary sites of replication that can cause problems?

Answer 9

Kidney/seminiferous tubules: temporary infertility in stallions
Placenta: infect fetus and cause fetal death by severe necrotizing myometritis and placental detachment

Question 10

What are clinical signs of EVA in adult horses?

Answer 10

Most asymptomatic
Fever, depression, anorexia, limb edema (hind limbs), preputial edema
Urticaria

Question 11

What are clinical signs of EVA in neonatal foals?

Answer 11

Severe interstitial pneumonia and/or enteritis

Question 12

T or F: mares can abort pregnancy if a natural outbreak of EAV occurs?

Answer 12

True..

Question 13

What is stallion ‘subfertility?’

Answer 13

Not due to the direct effect of the virus but due to intratesticular temperature increase and extensive scrotal edema

Question 14

What signs would you see at necropsy that would help you diagnose this condition?

Answer 14

Edema, congestion and hemorrhages of subcutaneous tissues, visceral organs, lymph nodes

Question 15

Is there a vaccine available? How is it best used?

Answer 15

Yes, colts vaccination can be done at 6-8 mos of age, non-carrier stallions should be vaccinated annually! At least 4 weeks before breeding season
Carriers should only be bred to vaccinated females

Question 16

What is another name for porcine reproductive and respiratory syndrome (PRRS)?

Answer 16

Swine mystery disease (SMD) or Blue Ear Disease

Question 17

How is PRRS transmitted?

Answer 17

Aerosols, direct contact, infected semen, transplacental

Infected piglets can be born viremic and transmit virus for 112 days after infection!!

Question 18

Where is the primary site of replication for PRRS?

Answer 18

Macrophages in lungs and lymphoid tissues!

Question 19

What are the characteristic lesions of acute PRRS infection?

Answer 19

Lymph node enlargement and interstitial pneumonia

Question 20

What are the two phases of PRRS?

Answer 20

Reproductive failure and post weaning respiratory diseases

Question 21

Describe the reproductive failure phase:

Answer 21

Late term abortions, still births, mummified fetuses, premature farrowing, birth of weak piglets
Umbilical cord lesions primarily

Question 22

Describe the post weaning respiratory disease phase:

Answer 22

Severe respiratory distress, characteristic thumping respiratory pattern, severe necrotizing interstitial pneumonia
Labored breathing, fever, loss of appetite, red discoloration of body and BLUE EARS!

Question 23

What is the most common diagnostic method for PRRS?

Answer 23

ELISA to measure IgG antibodies to PRRS virus

Question 24

How is PRRS controlled?

Answer 24

Live-attenuated and inactivated vaccines are commercially available
Control of this virus by exclusion because virus spreads between herds by movement of infected swine/semen