Parvoviridae

Question 1

Disease mechanisms of B19 parvovirus

Answer 1

Spread by respiratory and oral secretions,
Infects mitotically active erythroid precursor cells in bone marrow and establishes lytic infections,
Establishes large viremia and can cross the placenta.

Question 2

Parvovirus causes

Answer 2

Biphasic disease.
Initial phase is related to viremia: influenza-like symptoms (ILS) and viral shedding

Later phase is related to nonifectious immune response: circulating immune complexes of antibody and virions that do not fix complement.
Result: erythematous maculopapular rash, arthralgia, and arthrtis.

Depletion of erythroid precursor cells and destabilization of erthrocytes imitate aplastic crisis in people with chronic anemia.

Question 3

Parvovirus disease factors

Answer 3

Capsid virus is resistant to inctivation.
Contagious period precedes symptoms.
Virus causes placenta and infects fetus.

Question 4

Modes of control for parvovirus

Answer 4

None

Question 5

Typical of the rash for erythema infectiosum

Answer 5

Slapped-cheek appearance

Question 6

Parvovirus disease

Answer 6

Erythema infectiosum.
The third stage of Fifth’s disease begins as the rash starts to fade with areas of central clearing. This leaves a reticulated or lacy pattern of erthema which can last several weeks.

The most common complication is joint involvement ranging from mild arthralgias to overt arthritis.

Question 7

Describe paroviridae

Answer 7

Smallest DNA virus,
Naked icosahdreal capsid,
Single stranded DNA genome,
Requires growing cells (B19) or helper virus (dependovirus) for replication