Exam 2 - Family: Circoviridae

Question 1

Family: Circoviridae

Answer 1

Include the genuses

1. Circovirus
2. Gyrovirus

Question 2

Genus: Circovirus Diseases

Answer 2

1. Psittacine beak and feather disease virus
2. Porcine circovirus type-1 (non-pathogenic)
3. Porcine circovirus type-2 (Post-weaning Multisystemic Wasting Syndrome - PMWS)

Question 3

Genus: Gyrovirus Diseases

Answer 3

Chicken infectious anemia virus

Question 4

Family: Circoviridae - Properties

Answer 4

Small viruses, 17-22 nm, circular single-stranded DNA genomes. Virus replication occur in actively dividing cell. DNA replication occurs int he nucleus and requires cellular proteins and other components produced during the S phase of the cell cycle. Virions are very stable, resisting 60oC for 30 minutes and pH 3 to 9.

Question 5

Genus: Circovirus - Properties

Answer 5

Has a circular single stranded ambisense DNA

Question 6

Genus: Gyrovirus - Properties

Answer 6

Has a circular single stranded negative sense DNA. Chicken infectious anemia virus have 12 trumpet like structures that are less obvious in other circoviruses.

Question 7

PMWS - Hosts

Answer 7

Most common in pigs at 4-6 weeks of age or 2-3 weeks post weaning

Question 8

PMWS - Transmission

Answer 8

Fecal-oral transmission is most common. Virus is found in all secretions. Vertical transmission (transplacental infection). Fomites.

Question 9

PMWS - Pathogenesis

Answer 9

Individual coalescing foci of granulomatous inflammation in lymphoid tissues, lungs, liver, kidney, heart and intestines.

Contain prominent “botryoid” (grape like) intracytoplasmic inclusion bodies in virus infected macrophages.

Lymphoid depletion

Question 10

PMWS - Transplacental Infection

Answer 10

Infection during the first and second trimesters results in fetal death and resorption or aborted fetuses with severe cardiac congestion. Infection during last trimester has minimal effects on fetuses.

Question 11

PMWS - Clinical signs

Answer 11

Lethargy, progressive weight loss, cough, dyspnoea, slow growth, lymphadenopathy, diarrhea, skin discoloration, congenital tremors, icterus.

Question 12

PMWS - Co-infection

Answer 12

With porcine parvovirus (PPV), porcine reproductive and respiratory virus (PRRSV) and opportunistic bacteria may cause severe disease and more pronounced lesions.

Question 13

PMWS - Vaccination - Chimeric vaccines

Answer 13

New generation chimeric vaccines have been developed that utilize the non-pathogenic porcine circovirus-1 (PCV-1) as a genetic backbone for expression of the immunogenic capsid protein of PCV-2.

Question 14

PMWS - Vaccination - Inactivated or baculovirus-expressed vaccines

Answer 14

Virus like particles that include the capsid protein of PCV-2 are also available as vaccines.

Question 15

PMWS - Vaccination - vaccine schedules

Answer 15

• Piglets are either 1 or 2 doses with the 1st dose at 3 weeks of age, and second dose 3 weeks later
• Sow vaccination - 2 and 5 weeks antepartum.

Question 16

Porcine Dermatitis and Nephropathy Syndrome (PDNS)

Answer 16

Associated with PCV-2. Sporadic, and reported in older piglets. Findings include necrotizing skin lesions, vasculitis, and fibrinous glomerulonephritis. Hemorrhagic necrosis of the skin.

Question 17

Chicken Infectious Anemia - Host

Answer 17

Highly contagious to young chicks (2-4 weeks of age). Older chickens more resistant to clinical disease.

Question 18

Chicken Infectious Anemia - Transmission

Answer 18

Virus is shed in feces and feather dander. Horizontal transmission through inhalation or oral exposure. Transmitted vertically through egg. Environmentally stable virus, remains in contaminated fomites for long periods.

Question 19

Chicken Infectious Anemia - Pathogenesis

Answer 19

Hemocytoblasts in the bone marrow, precursor T cells in the cortex of the thymus, and dividing CD4+ and CD8+ cells in the spleen. Apoptin protein of CAV virus induce apoptosis. Immunosuppression and aplastic anemia. Vulnerable to secondary bacterial and fungal infections.

Question 20

Chicken Infectious Anemia - Clinical Signs

Answer 20

Chicks are anorectic, lethargic, depressed, reduced body weight gain, and pale. Blood may be watery and clot slowly as a result of thrombocytopenia. Subcutaneous hemorrhages and skeletal hemorrhages, pale muscles.

Question 21

Chicken Infectious Anemia - Diagnosis

Answer 21

Examination of PCV. Low PCV, examination of blood for total erythrocytic count will reveal anemia, thrombocytopenia, blood watery and will clot slowly.

Question 22

Chicken Infectious Anemia -Vaccination

Answer 22

Aim of vaccination is to protect the progeny from vaccinated breeders from early infections by means of maternally derived antibodies. Live vaccines are available