Elementary Virology - Answers

Arlo Guthrie — Mon, 20 Apr 2009 13:50:27 GMT

Current Revision posted to Revision Guide For Student Nurses - Part 2 by Arlo Guthrie on 4/20/2009 1:50:27 PM

ANSWERS

What type of microscope is employed for the examination of viruses and why?
An electron microscope. Viruses are tiny and it is impossible to view them under a normal light microscope.
List 4 characteristics common to all viruses.
- Obligate parasites.
- Reproduce by replication and are incapable of reproduction without a host cell.
- Extremely small in size (20-300nm in diameter).
- Carry DNA or RNA but never both.
What is a virion?
An inert virus outside of the host; an infectious form which carries genetic material from one cell to another.
Name the 2 main parts of a virus which comprise the nucleocapsid.
- Central core of nucleic acid (DNA or RNA) known as the genome.
- Protein coat known as the capsid.
  Some viruses also have a lipoprotein membrane forming a surrounding envelope.
What is the name of the individual protein structure units which comprise the capsid?
Capsomeres.
List 4 shapes of nucleocapsid.
- Helical (e.g. distemper).
- Icosahedral (e.g. parvovirus).
- Complex (e.g. poxvirus).
- Composite (e.g. some bacteriophages).
List 4 naked virus families.
- Adenoviridae.
- Papoviridae.
- Parvoviridae.
- Reoviridae.
List 4 enveloped virus families.
- Coronoviridae.
- Herpetoviridae.
- Retroviridae.
- Rhabdoviridae.
State the method by which viruses reproduce.
Replication; the virus invades a susceptible host cell, takes over control of the metabolism and produces copies of itself.
Briefly describe the method by which viruses reproduce.
- Virus attaches to receptor sites on host cell membrane and fuses with it.
- Virus enters host and capsid breaks down to release nucleic acid.
- Nucleic acid replicates (either in the host's cytoplasm or nucleus) and directs the host cell metabolism to create new virus material.
- New virus are assembled and leave the host cell by budding through or rupturing the cell membrane.
Why are viral infections difficult to control?
- Drugs that interfere with viral replication usually have a harmful effect on the host cells.
- Incubation periods are often lengthy, and thus symptoms may only be seen once large numbers of virus particles have infected a large number of cells.
What supportive nursing techniques might you employ in the case of a patient suffering a viral infection?
- Fluid therapy.
- Assisted feeding.
- Antibacterial therapy to limit secondary infection.
How might the spread of viral infection be prevented?
- Barrier nursing.
- Isolation.
- Quarantine.
- Disinfection.
- Sterilisation.
- Immunisation.
What is a prion?
A tiny, infectious protein particle responsible for infections within the central nervous system.
Give an example of a rare prion disease seen in cats.
Feline spongiform encephalopathy (FSE).