Families: Circoviridae and Anelloviridae Flashcards
What is the smallest known viral pathogen of animals?
Circoviridae
What kind of genome does Circoviridae have?
circular ssDNA
What is the structure of Circoviridae? How does it replicate?
non-enveloped, icosahedral capsid
rolling circle replication - unidirectional NA replication that rapidly synthesizes multiple copies of circular DNA
Where is the origin of replication of Circoviridae located?
between the start point of 2 ajor divergently arranges ORFs (-CAP and CP)
Where is the origin of replication of Circoviridae located?
between the start point of 2 major divergently arranges ORFs (-CAP and CP)
What gene is responsible for the synthesis of the ORFs near Circoviridae’s origin of replication?
rep
Where does Circoviridae replicate? What are the 5 steps?
in the host’s nucelus
- virus penetrates host cell
- uncoats and releases viral genomic ssDNA into nucleus
- ssDNA —> dsDNA
- viral mRNA is transcribed and translated into protein
- newly synthesized ssDNA can either act as a template for transription/translation, or be encapsidated to form virions to be released via budding
What is Psittacine Beak and Feather Disease? In what 3 ways is it transmitted?
contagious, fatal viral disease (Circoviridae) affecting the beaks, feathers, and immune system of psittacines
- direct contact
- inhalation or ingestion of aerosols
- infected fecal material and feather dust
What are the 3 forms of Psittacine Beak and Feather Disease?
- PERACUTE: affects neonatal parrots, causing septicemia, pneumonia, enteritis, weight loss, and death (may die before feather abnormalities)
- ACUTE: affects young birds during their first feather formation, causing depression and sudden changes in developing feathers (color, bending, breaking, bleeding, shedding)
- CHRONIC: loss of production of powder down, beak may soften and rot away
What is the best diagnostic approach of Psittacine Beak and Feather Disease?
detection of viral genome on whole blood sample
How is Psittacine Beak and Feather Disease prevented and controlled?
- elimination or quarantine of carrier birds to prevent transmission
- vaccines (not available worldwide)
What causes porcine multi-systemic wasting syndrome? What are 5 signs?
Porcine Circovirus-2
- wasting or ill thrift
- extremely enlarged lymph nodes
- rubbery lungs with interlobular edema
- enlarged liver
- white spots on kidney caused by interstitial nephritis
How do Porcine Circovirus-1, 2, and 3 compare genetically?
CPV-1 and CPV-2 show a high degree of sequence identity and similar genomic organization, while CPV-3 has a similar genome organization, but the sequence identity is much lower
What causes porcine dermatitis and nephropathy syndrome? What are 2 signs?
PCV
- necrotizing skin, usually red to purple in color
- enlarged kidneys with petechial and/or multifocal areas of necrosis
How do Porcine Circoviruses affect the reproductive system?
- abortions and stillbirths
- piglets with enlarged hearts and livers at necropsy
What are 2 characteristics of PCV-2 systemic disease?
- presence of PCV-2 antigen or DNA in microscopic lymphoid lesions
- presence of gross and microscopic lesions characteristis of the disease
How is Porcine Circovirus infection controlled?
- minimize stress
- clean, healthy environment and facilities
- minimize mixing, moving, and density
- eliminate or diminish co-infections
- oral or injectable anti-inflammatories
- all-in all-out management
Why was Anelloviridae originally named TT virus? What is its genome like?
- initials of original patient infected
- “transfusion transmitted virus”
circular ssDNA
(torques = necklace; tenuis = thin)
What causes chicken infectious anemia? What are the typical signs?
Gyrovirus in the family Anellovirus (originally part of Circoviridae)
young (commercial) chickens with aplastic anemia, generalized lymphoid atrophy and profound immune suppression that leads to secondary viral, bacterial, and fungal infection
How is chicken infectious anemia transmitted? What economic impact does it have?
trans-ovarian (vertical)
through infected organic material or equipment (oral, respiratory)
- poor food conversion rate
- reduction in weight gain
- high contamination rates for carcasses in the slaughter house
What organ affinity does chicken infectious anemia virus have? At what age is infection most common?
thymus (also seen in spleen, bursa, and bone marrow)
first 3 weeks of life
What 2 cells does chicken infectious anemia virus typically infect?
- hemocytoblasts
- T lymphocyte precursors
What are 4 common clinical signs of chicken infectious anemia?
- lethargic, depressed, and pale chicks
- older chicken appear less developed for their age
- chicks huddle under heat source constantly
- hemorrhage in musculature and subcutaneous wing tips
What are 5 common postmortem lesions caused by chicken infectious anemia?
- ecchymosis and skin hemorrhages in young chicken resulting in blue discoloration of hock
- subcutaneous hemorrhages and petechial bread of young chicken
- pale anemic carcass
- thymus atrophy
- pale, yellow bone marrow (fatty)
How is chicken infectious anemia diagnosis confirmed? How is infection controlled?
detection of virus or vrial DNA in thymus or bone marrow —> PCR, commercial ELISA kits
live vaccines for antibody-negative breeder flocks during the rearing period (8-16 weeks)
In what animal is Torque Teno virus infection highly prevalent? How is it primarily transmitted? How does it affect the economy?
pig populations worldwide
fecal-oral route
may worsen the progression of other diseases and increase economic losses
