CIRCOVIRIDAE

Question 1

Circoviridae is the smallest RNA virus. True or False?

Answer 1

False, DNA.

Question 2

Give the virion properties of Circoviridae.

Answer 2

• Circular single-stranded DNA
• String of pearls
• Replication: nucleus; rolling circle mechanism
• Nonenveloped
• Icosahedral symmetry

Question 3

What are the associated diseases of Beak and Feather disease?

Answer 3

1. Permanent loss of feathers
2. Beak and claw deformities when in captivity (beaks: shiny, overgrown, or broke, exhibiting delaminations, or with palatine necrosis)
3. Abnormal pin feathers
4. Abnormal mature feathers (retention of sheaths, blood in shaft, fracture or rachis)
5. Severe leukopenia and nonregenerative anemia (without feather lesions)

Question 4

What is the pathogenesis of Beak and Feather disease?

Answer 4

1. Tropism for rapidly dividing cells (e.g. basal epithelial layer of feather follicles, beak, and claw, lymphoid tissues, intestinal epithelium
2. Characteristic basophilic intracytoplasmic (botryoid) inclusions occur in follicular epithelium
3. Necrosis and inflammation with dystrophic feathers
4. Lymphoid depletion

Question 5

What are the histopathological findings described in Beak and Feather disease?

Answer 5

• Virions resemble the previously described porcine circovirus 1
• Basophilic intracytoplasmic (botryoid) inclusions occur in follicular epithelium
• Necrosis and inflammation with dystrophic feathers

Question 6

Porcine circovirus 1 is non-pathogenic. True or False?

Answer 6

True

Question 7

What are the associated diseases of Porcine circovirus 2?

Answer 7

*** PCVAD syndromes
- Post-weaning multisystemic wasting syndrome
- Porcine dermatitis and nephropathy syndrome
- Porcine respiratory disease complex (bronchointerstitial pneumonia associated with combinations of pathogens, including M. hyopneumoniae)
- Reproductive failure
- Granulomatous enteritis
- Exudate epidermitis
- Necrotizing lymphadenitis

*** Progressive weight loss or decreased rate of weight gain, paleness or icterus, ill thrift

Question 8

Give the pathogenesis of Porcine circovirus 2.

Answer 8

** Coinfections enhance PCV2 replication & pathogenicity: Porcine Parvovirus, Swine Influenza virus, PRRSV, M. hyopneumoniae
** Torque Teno sus viruses (TTSuVs) implicated in PCVAD pathogenesis
** Take Note: The common feature of these infections is immune activation, which somehow enhances the replication of porcine circovirus 2 in a variety of target cells. Thus, PCVADs are apparently exacerbated by the immunostimulation that results from co-infecting pathogens, or even from the immunostimulatory action of adjuvants such as keyhole limpet hemocyanin.
** PCVAD identified as postweaning multisystemic wasting syndrome lesions: Granulomatous inflammation in lymphoid, lungs, liver, kidney, heart, and intestines, “botryoid” inclusion bodies, lymphoid depletion
*** Porcine Dermatitis Nephropathy Syndrome (PDNS): Infarctive skin/ Ischemic necrosis lesions (rear legs), vasculitis, glomerulonephritis

Question 9

What are the histopathological findings in Porcine circovirus 2?

Answer 9

1. Macrophages with botryoid inclusions
2. Paracrystalline viral array in inclusions