Parainfluenza

Question 1

parainfluenza

Answer 1

paramyxoviridae virus

Question 2

Characteristics

Answer 2

1. Ubiquitous { Single most freguesnt cause of acute larngotracheobronchitis / croup]
   May also cause pharyngitis, bronchitis or rhinitis
2. Two serotypes : respirovirius (1,3) and rubelavirus (2,4)
3. Has Hemoagglutinin, Neuraminidase and F protein
4. Hemolysin is present and produces cytoplasmic inclusion bodies
5. PIV types 1,2,3 associated with lower respiratory tract infections in children
6. Grow well in primary monkey or human epithelial tissue
7. Produce minimal cytopathic effect
8. Grow poorly in embryonated eggs

Question 3

Pathogenesis

Answer 3

Virus enters through direct person to person contact or respiratory droplets pr aerosols
Replication causes cytolysis of respiratory mucosa

Question 4

Immunity

Answer 4

All breastfed infants would have antibodies
Antibodies do not provide life long immunity ( Reinfection in adults occurs in the presence of antibodies)
Antibodies only modify the disease
Natural infection stimulates IgA antibodies in mucus ofor a few months
Antibodies do not provide protection, they only modify the disease.

Question 5

Why is there reinfection in children?

Answer 5

Serum antibodies to HN and F on envelope neutralise infectivity
Infants produce local IgA antibodies that do not neutralise virus and have weak response to F protein

Question 6

Epidemiology

Answer 6

Primary infection occurs in early childhood
PIV 3 more prevalent - Causes pneumonia and bronchitis in children under 6 months
PIV 1 and 2 cause croup in children
Exacerbates bronchial asthma
Shedding lasts 3-10 days

Question 7

Treatment

Answer 7

Ribavirin as an aerosol

No vaccines

Question 8

Laboratory diagnosis

Answer 8

Specimen
Throat and nasal swab
Nasal wash and secretions

Antigen detection
RNA by RT-PCR