Viruses
can infect every type of living thing including flowering plants, mammals and
bacteria!
Like bacteria they come in a variety of different shapes,
including helical, envelopeand even more complex. Viruses are smaller in size than bacteria
(about 1% of the size on average). The
largest being pox viruses which are about the same size as bacteria.
Each virion (virus particle) is made up of:
·
a core: made up of 1 or 2 DNA
or RNA molecules
·
a capsid: a protein coat which enloses the
core, it protects the genetic material (DNA) and helps it transfer from host to
host ie: spread
·
an envelope: only some viruses have this
additional layer which surrounds the capsid
Viruses can only reproduce when inside a living cell and this
will also cause damage to the cell. The
virus attaches to a 'receptor ' on the cell
surface, different viruses can only attach to certain cells eg: flu virus
attaches to the cells lining the lungs and airways. The virus then 'injects' its RNA or DNA into
the cell where it uses the enzymes to make new virus particles (replicate). The number of virus particles will eventually
kill the cell and they will then be free to move around the body infecting
other cells.
As the virus infects and kills more cells, symptoms will
begin to appear and this will continue until the immune system is able to fight
the virus and overcome it. Some viruses will spread from horse to horse via
biting flies or other biting insects.
Other viruses are spread through droplets from coughing or
sneezing! More seriously some viruses
are airborne!
Many viruses can be dealt with by the immune
system. Vaccinations (before the
horse contracts the virus) can help the immune system recognises the virus more
quickly and so overcome it more quickly but antibiotics DON'T work on viruses.
Some viruses will lie dormant within the body and this can
also help the horse develop immunity.
Viruses are usually 'host specific' so we can't catch horse flu,
however, Rabies
is an important exception and can transfer from species to species.
UK Equine Viruses include:
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Until next time!
Jo
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