Tuesday, 13 September 2011

Viral Diseases in Animals

Viral Diseases in Animals
Viruses carry out no independent metabolism: they do not respirate, they do not process nutrients, they do not generate waste products, and they rely on living cells of the host for their reproduction. A virus outside a cell is an inert bit of particulate matter; once inside, however, the virus seizes command of the cell's biosynthetic machinery, converting the cell into a "high-tech" factory for the production of new virus particles.

Many viruses eventually kill their host cells, resulting in disease and provoking an assault by the immune response of the host. Sometimes, this response goes away, so that the harmful effects of the immune response are actually more serious than those of the viral disease itself Other viruses provoke little, if any, reaction, and some can remain dormant, or latent, in the host for years. The vast majority of all virus infections appear to be asymptomatic in nature that is, the infections are so mild and the host response so effective that clinical signs of disease never develop.

Very few viral diseases are responsive to specific antiviral therapy. Instead, the secondary effects of a viral infection are addressed in an effort to protect the host against secondary bacterial or fungal infection while the immune response to the virus is developing. Most successful attacks against viral invasion are carried out by the body itself The most effective therapy for viral diseases is prevention, that is, vaccination. Most antibiotics and antifungals have no effect on viruses; clinically useful drugs with specific antiviral activity are still relatively few in number and restricted almost exclusively to some very specific virus infections.


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