Arteriviruses Flashcards
What is the order and family of arteriviruses?
- Order- Nidovirales
- Family-Arteriviridae
What is the genome organisation of arteriviruses?
- Single-Stranded RNA
- Positive Sense
What is the arterivirus virion structure?
- Singular nucleocapsid protein
- 6 different enveloped proteins
What are the two cellular receptors of arteriviruses?
- Heparin-like molecules
- CD163 and sialoadhesins
What are the virus counterparts of arterivirus?
Sialic acid in glycan chains of GP5/M and GP2/3/4 trimers
What cell types do arteriviruses target?
- Macrophages, Monocytes, lymphocytes, endothelial cells
What effects do arterivirus have on the infected cells?
- Necrosis or apoptosis directly
- Supression of type-I interferons
How do arteriviruses replicate?
- Attach to the host receptors
- Fusion of virus membrane with the host membrane
- ssRNA genome is released into the cytoplasm
- Synthesis and proteolysis of replicase polyproteins
- assembly of new virions via exocytosis
What are the three most important things surrounding arterivirus pathogenesis?
- Dysregulation of cytokine production via macrophages
- Immuno-supression
- Persistent Infection
What does equine Arterivirus cause?
Equine Viral Arteritis
What are the Clinical Symptoms of Equine Arterivirus?
- Death- in old young or immunocomprimised horses
- Abortion rate of between 10-60%
- Influenza-like symptoms in adult horses (lethargy and stiff movement)
How does EAV transmit horizontally?
Aerolisation of respiratory tract secretions
How does EAV transmit venereally?
- Acutely infected mares
- Acutely and chronically infected stallions
- Natural service and artificial insemination
How does EAV transmit vertically?
- Transplacental transmission, especially when mares get infected late
- results in abortion, fatal interstitial pneumonia,
- Fibronecrotic enteritis
When do the viruses become inactivated?
- 20-30 mins at 56-58ºC
- 2 to 3 days at 37-38ºC
- Up to 75 days at 4-8ºC
What happens when EAV infects monocytes/ macrophages?
release of pro-inflammatory cytokines and TNF-alpha
dysfunction of the vascular endothelium and systemic pathology, pyrexia, cachexia, lipolysis
What effects the severity of the EAV virus?
- Virus Strain
- Horse Breed
- Donkey species
What are the clinical signs of EAV in stallions
- Decreased Fertility
- Reduced sperm quality
- Caused by increased scrotal temp and edema
- Decreased libido
What samples may you take for EAV?
- Nasal secretions
- Blood
- Semen
How would you detect antigens?
- Virus isolation
- Nucleic acid detection
- Immunohistochemistry
How would you detect antibodies?
Serology
Virus neutralisation
ELISA
fluorescent antibody
Fluorescent microsphere immunoassay
How would you manage the venereal transmission?
- Separate pregnant mares from other horses
- Isolate new arrivals
- Breed carrier stallions only to well vaccinated or seropositive mares
How would you prevent/ control transmission in carrier stallions?
- Physically isolate from uninfected horses
- Clean and disinfect fomites
- Testing and identification
- there is no specific treatment other than surgical castration
What is the genus of PRRS?
Single stranded positive RNA (arterivirus)
How many proteins does the PRRS genome encode?
7 proteins
What are the two distinct PRRS genotypes?
- European
- American
What are the three PRRS subtypes?
- Attenuated strain
- Immuno-Supressive (type I)
- Inflammatory (type II)
What are the primary target cells for PRRSV tropism?
- Monocyte/ Macrophage lineage
- infects different subsets of differentiated macrophages in the lungs, lymphoid tissue and placenta
How is PRRSV transmitted?
* Horizontal transmission
* From contaminated food
* Vertical transmission
* Through transplacental transmission
* Venereal transmission
* During breeding with semen from PI boars
* lateral transmission
* Through fomites or personnel
* Mechanical vectors.
* Flies and mosquitoes might serve as mechanical vectors
What is the pathogenesis of PRRS?
- Infection via aerosols/ fomites
- Mucousal surfaces or lung macrophages
- Draining regional lymph nodes
- Target organs are the lung, thymus, uterus, placenta and testis
What are the clinical signs of PRRS in young pigs?
- Dyspnoea, nasal exudate
- Slow growth
- Reddening of the skin
- Loss of appetite and lethargy
What are the clinical signs of PRRS in pregnant sows?
- Dyspnoea
- Lethargy
- Loss of appetite
- Abortion, stillborn pigs, mummified foetus, weak pigs
What are the clinical symptoms of PRRS?
- Fever
- Mild respiratory distress
What samples would you take to determine PRRS?
- Whole blood EDTA
- Serum
- Lung/ Respiratory tract
- Spleen and tonsils
What are the three subtypes of PRRS virus?
- Attenuated
- Immuno-suppressive
- Inflammatory
