Picornaviridae

Questions

1. Describe the general properties of this group of viruses

2. What are two main subtypes of this group, describe in detail?

3. How would you prevent polio.

4. Coxsackie virus has several groups, describe the pathological conditions associated with each?

5. How would you diagnose and treat coxsackie viruses?

Picornavirus are 20-30nm, icosahedral, enveloped, ss, +ve polarity. There are two main groups based on resistance to ph between 3-5 and habitat. 1^st group is rhino viruses, 2^nd group is enteroviruses. Note that enteroviruses do not cause gastroenteritis. The former has more than 100 serotypes, which cause common cold infections, upper and lower respiratory tract infections and bronchiolitis in infants. Development of vaccine is unlikely. The latter has different viruses. The polio virus causes poliomyelitis in adults. There are 3 serotypes of which, only A is highly virulent, has a faecal oral route of spread. It penetrates the intestinal mucosa and then spreads to regional lymph nodes. In some cases, further multiplication may cause viraemia, and sometimes may infect the meninges causing meningitis. It may also spread to the anterior horn of the spinal cord, causing motor neurone lesions, or to the brain cause poliomyelitis or polioencephalitis. Prevention is by an oral vaccine, live, attenuated, sabine vaccine. Covers the three polioviruses, give at 2, 4, 6 months, again at 4-6 yrs and then again at 12-15yrs old. Earlier a dead Salk vaccine was used.

The Coxsackie virus is another group belonging to the enterovirus group. It has four different types: A, B, Echo virus, Enteroviruses. These have 24, 6, 34,& 4 serotypes respectively. Type A causes (HH) – herpangina, hand/foot & mouth disease. Type B causes (BMPPP): Bornholm’s disease (epidemic myalgia  muscular pain), Myocarditis, pericarditis, pancreatitis, poliomyelitis like illness. Enterovirus type 68, 70, 71 cause: (PAE): Pneumonitis, bronchiolitis, acute haemorrhagic conjunctivitis, encephalitis. Diagnosis is isolation of virus in faeces, sometimes throat and CSF specimens required. Use serology to confirm for antibodies. Pleconaril is a new anti-viral inhibits several types of picornaviruses by binding irreversibly to viral capsid.

Category: Microbiology Notes