Families: Arteriviridae & Roniviridae Flashcards
What is the morphology of Arterivirdae’s virion? What is its genome like?
spherical, with a smooth surface envelop and a ring-like structure
ssRNA positive sense
Where does Arterivirdae replicate? How does the virion form?
cytoplasm
buds into the rER and is released by exocytosis
What are 4 common Arteriviridae viruses that cause significant disease?
- equine arteritis virus (EAV)
- porcine reproductive and respiratory syndrome virus (PRRSV)
- lactate dehydrogenase-elevating virus (LDV) of mice breeding colonies
- simian hemorrhagic fever virus (SHFV)
What are the tropisms of equine arteritis virus (EAV) and porcine reproductive and respiratory syndrome virus (PRRSV)?
- macrophages (monocytes)
- respiratory and reproductive tracts
Arteriviridae replication cycle:
What order, family, and genus does equine arteritis virus (EAV) belong to?
Nidrovirales
Arteriviridae
Arterivirus
What species does equine arteritis virus (EAV) affect?
horses, donkeys, zebras, ponies (no outbreaks in mules reported)
- isolates vary in virulence
- only one serotype
- 10-70% infected stallions become carriers
What is the prevalence of equine arteritis virus (EAV) in horse breeds? What likely causes this?
Standardbreds > Thoroughbreds > Warmbloods > Quarterhorses
management practices
What are the 3 modes of transmission of equine arteritis virus (EAV)?
- RESPIRATORY - common where horses gather, like racetracks, sales, and shows
- VENEREAL - acutely infected mares and acutely/chronically infected stallions, typically via natural service and artificial insemination
- IN UTERO - fomites (equipment), mechanical (humans, other animals)
How does freezing infecting semen affect equine arteritis virus (EAV)?
no effect - semen remains infectious
What 4 things were observed in experimental infections of equine arteritis virus (EAV)?
- fever
- depression
- serous ocular and nasal discharge
- pregnant donkeys did not abort
Equine arteritis virus (EAV) transmission:
When are asymptomatic infections most commonly observed in equine arteritis virus (EAV)? Severe infections?
mares bred to long-term carriers
foals with respiratory signs and enteritis
What disease is seen in adults, pregnant mares, and stallions infected with equine arteritis virus (EAV)?
fever, depression, anorexia, edema
abortion, stillbirth
decreased fertility (acute), reduced sperm quality caused by increased scrotal temperature and edema, decreased libido
What are common postmortem lesions associated with equine arteritis virus (EAV) in acute cases, foals, and aborting mares?
edema, congestion, hemorrhages, fluid accumulation in body cavities
pulmonary edema, interstitial pneumonia, splenic infarcts, enteritis
endometrial hemorrhages, autolyzed fetus
What is the pathology of equine viral arteritis?
- EAV infection (respiratory, venereal, in utero)
- EAV in macrophages 24 hours PI
- EAV in satellite lymph nodes 48 hours PI
- EAV in endothelium and circulating monocytes 3 days PI
- systemic distribution of EAV and male carrier state
- EAV in blood vessel endothelium and medial myocytes 6-8 days PI
- severe damage to blood vessels 10 days PI and abortion of infected newborn
- EAV in renal tubular epithelium and shedding in urine 10-21 days PI
How can laboratory diagnosis of equine arteritis virus (EAV) occur?
- virus isolation from semen from a carrier stallion on rabbit kidney cells
- nucleic acid (RNA) detection in rtPCR
- antigen detection via IHC and histopathology
- serology: virus neutralization, complement fixation, agar gel immunodiffusion, indirect fluorescent antibody, fluorescent microsphere immunoassay, ELISA
How can carrier stallions be detected?
breeding to 2 seronegative mares
What are 9 differential diagnoses for equine arteritis virus (EAV) infection?
- equine influenza
- equine infectious anemia
- African horse sickness
- Hendra virus
- equine rhinitis A and B viruses
- equine adenoviruses
- equine herpesviruses 1 and 4
- purpura hemorrhagica
- Berteroa incana (hoary alyssum) poisoning
How is equine arteritis virus (EAV) infection controlled?
- modified live vaccine for breeding mares
- identification of persistently infected stallions
- no breeding of anti-EAV antibody positive mares
What 2 requirements should horses pass to be proven equine arteritis virus (EAV) negative and able to export?
- horses should be seronegative
- semen should be negative for virus isolation and rtPCR
What are the 2 major porcine reproductive and respiratory syndome virus (PRRSV) genotypes?
- European prototypes - EU-type I (Lelystad virus)
- North American prototypes - NA-type II (VR-2332); ENDEMIC
Porcine reproductive and respiratory syndrome virus (PRRSV) is constantly changing into different quasispecies. What do the European and North American strains share? What do they lack?
- 55-70% nucleotide identity at the genome level
- 50-80% amino acid similarity
- cross protection - immunity produced by one strain does not protect against the other
(LV and VR-2332)
In what 6 ways is porcine reproductive and respiratory syndrome virus (PRRSV) transmitted?
HORIZONTAL:
1. respiratory
2. fecal-oral
3. direct contact
VERTICAL:
4. trans-placental
5. semen (venereal)
6. artificial insemination
(spread every possible way)
Genome structure and organization of PRRSV:
- leader (ORF)
- RNA polymerase (1a, 1b)
- structural genes
7 strands of RNA
What are the primary target cells for replication of porcine reproductive and respiratory syndrome virus (PRRSV)?
porcine alveolar macrophages (PAM)
What 5 characteristics make the spread of porcine reproductive and respiratory syndrome virus (PRRSV) very easy?
- immunosuppressive
- PRSSV survives a long time in the cold and we conditions
- highly infectious - small amount is enough to infect entire herd
- persistent infection up to 200 days in some pig shedders
- easily mutated, making vaccine preparation hard
Why is it hard to tell between infected and vaccinated individuals with porcine reproductive and respiratory syndrome virus (PRRSV)?
difficult to differentiate - requires DIVA tests
What are 4 respiratory presentations of porcine reproductive and respiratory syndrome virus (PRRSV) infection?
- interstitial pneumonia with tan discoloration and mottling with a rubbery texture
- enlarged lymph nodes
- destruction of alveolar macrophages
- thumping - shallow and rapid breathing indicative of pneumonia
What are 5 reproductive presentations of porcine reproductive and respiratory syndrome virus (PRRSV)?
- abortion
- stillbirth
- mummification
- virus shed in semen
- impacts on semen quality
What presentation of porcine reproductive and respiratory syndrome virus (PRRSV) is common in the European prototype?
(EU type I - LV)
blue ear - edema and cyanosis
How can porcine reproductive and respiratory syndrome virus (PRRSV) infection be diagnosed?
- fluorescent antibody examination of frozen tissue
- PCR, especially in fetal materials from abortion
- restriction fragment length polymorphism
- virus isolation
- viral genome sequencing
- IHC
- ELISA
- immunoenzymatic staining assay: indirect immunofluoresence
- viral infection neutralization test
What is the purpose of the porcine reproductive and respiratory syndrome virus (PRRSV) vaccine?
decrease titer and duration of viremia/viral shedding
- modified live vaccine not safe for naive pregnant females
What are 4 management control measures that can prevent porcine reproductive and respiratory syndrome virus (PRRSV) infection?
- biosecurity (all-in-all-out)
- reduce concurrent infection
- replacement of gilts
- checking AI semen used
When was simian hemorrhagic fever virus first noticed? What are 7 clinical signs?
macaques imported from India in 1964
- fever
- facial edema
- anorexia
- dehydration
- skin petechiae
- diarrhea
- hemorrhage
How is simian hemorrhagic fever virus transmitted? What are the 2 target cells?
blood-to-blood transmission with 100% mortality within 5-25 days
- macrophages
- dendritic cells
What species can Toroviruses affect? What shape does it take?
equids, bovines, humans, swine
torus = circular convex molding (doughnut)
- capsid may be bent into an open torus, coferring a biconcave disk/kidney shape or may be straight, resulting in a rod-shaped particle
Torovirus (ToV) vs. Coronavirus (CoV):
What are 4 common Toroviruses?
- bovine torovirus Breda I
- equine torovirus strain Berne
- human torovirus
- porcine torovirus Merkelo
In what animals is porcine torovirus (PToV) most commonly found in? What was used to detect it? What else can be used?
piglets with diarrhea
immunoelectron microscopy
- neutralization assays
- indirect ELISA
- PCR**
What is the shape of Roniviridae virions?
enveleoped baciliform particles with a helical nucleocapsid composed of the nucelocapsid protein (p20) surrounded by a lipid envelop containing two transmembrane glycoproteins (gp64, gp116)
What is the genome of Roniviridae like? Where does it replicate?
non-segmented, positive-sense ssRNA with 5-6 long open reading frames
cytoplasm with nucleocapsids budding at the membrane of the rER and Golgi
Where is the primary Roniviridae of veterinary importance and its 2 genotypes? What does it typically infect? What are the primary natural hosts?
Okavirus - gill-associated virus, yellow-head virus
crustaceans - giant tiger shrimp (Penaeus monodon)
How does gill-associated virus (GAV) typically affect shrimp?
chronic infection in healthy brood stock and farmed black tiger prawns
