Reoviridae & Birnaviridae (Exam 2) Flashcards
What are the general properties of reoviridae?
Double stranded
Segmented RNA genome
Icosahedral/spherical
Two or three concentric layers
Non-enveloped
Arthropod-borne and enteric pathogens
What are the steps of reoviridae replication?
Attachment
Receptor-mediated endocytosis
Outer capsid removed = core particle
mRNAs transcribed and released into cytoplasm
Genomic RNA synthesis/protein translation (viral factories)
New virions form
Release via accessory protein or cell lysis
What is included in the “virus factory” or reoviridae replication?
Intra-cytoplasmic inclusion body = virus factory
Inside = mRNA, dsRNA, viral proteins
Virions form in and around perimeter
What causes the large amounts of diversity in reoviridae?
Reassortment
What are the (6) requirements of reoviridae reassortment?
- Sympatry (same environment)
- Ecology (same species)
- Co-infection (infect same cells)
- Packaging (into same virion)
- Replicative compatibility
- Fitness (as fit or more than parental strains)
What disease is caused by rotavirus?
“milk scours”
What are the symptoms of “milk scours”?
Diarrhea, dehydration, acid-base imbalance
What is the host specificity of rotavirus groups?
Species specific!!
What is the structure of rotaviruses?
3 layer icosahedron (but round)
What is the structure of the rotavirus genome?
11 segment dsRNA genome
What is the stability of rotaviruses?
Stable in the environment (non-enveloped)
Stable at low pH
Resistant to lipid solvents
What is the pathogenesis of rotavirus?
Attacks villus tip cells
Causes atrophy, loss of digestive enzymes, dip in absorption –> malabsorption –> diarrhea
What enterotoxin is produced by rotaviruses? What does it cause?
Enterotoxin = NSP4
Causes osmotic imbalance in crypt cells, leading to secretory diarrhea
What age does rotavirus infect?
Neonatal/perinatal animals
2d to 8w of age
What clinical signs are associated with rotavirus?
Watery diarrhea, dehydration
Anorexia, depression, vomiting
+/- death due to severe dehydration or second infection
How is rotavirus transmitted?
Horizontal: fecal-oral route
What is the incubation period of rotavirus?
Quick
1-24 hours
What is the host range of rotavirus?
Every animal on earth
What are the risk factors to infection of rotavirus?
Poor sanitation
Lack of maternal immunity
Failure of passive transfer
What factors can increase morbidity of rotavirus?
Chilling, overcrowding
Other pathogens: E. coli, coronavirus, cryptosporidia
How is rotavirus diagnosed?
Latex agglutination (feces)
Histopathology
ELISA
PCR
How is rotavirus immunity acquired?
Good colostrum/milk quality and feeding
Vaccination or natural infection of dams
What sanitation/hygiene methods are used in prevention/control of rotavirus?
Disinfection of pens, feeding utensils, etc.
Rotavirus is not readily inactivated
Pasture rotation in range cattle operations
What (3) orbiviruses are listed by the World Organization of Animal Health?
Bluetongue virus
Epizootic hemorrhagic disease virus
African horse sickness virus
What cell types are targeted by orbivirus?
Endothelial cells!
Reticuloendothelial cells (macrophages, dendritic cells)
What is the pathogenesis of orbivirus?
Vasculitis
Vascular leakage
What are the pathological signs lesions of orbivirus?
Edema
Hemorrhage