axoplasmic transport in spread of disease
Some infections that affect the
nervous system travel along nerves.
Rabies is a disease (often fatal) caused by a bite of a
rabid dog (and some other animals including monkeys). The saliva of an infected
animal contains the rabies virus. The virus travels from the site of the bite
to the central nervous system, along nerves, by reverse axoplasmic flow and
causes infection there. As this means of transport is slow there is a delay of
a few days between the bite and appearance of symptoms. The duration of this
delay depends on the length of the nerve fibres concerned. A bite on the face
produces symptoms much faster than one on the foot.
The virus of poliomyelitis is also transported (from the
gastrointestinal tract) to the nervous system through reverse axoplasmic flow.
In contrast tetanus travels from the site of infection to
the brain through spaces in the endoneurium of nerve fibres.