Rabies
Rabies is an infectious disease of animals which is a member of a group of viruses
constituting the family Rhabdoviridae. The virus particle is covered in a fatty membrane,
is bullet-shaped, 70 by 180 nanometres and contains a single helical strand of
ribonucleic acid (RNA).
Although rabies is usually spread among domestic dogs and wild carnivorous animals, all
warm-blooded animals are susceptible to infection. The virus is often present in the
salivary glands of infected animals, referred to as rabid, and is excreted in the saliva.
The bite of the infected animal easily introduces the virus into a fresh wound. In
humans, rabies is not usually spread from man to man, rather the majority of infections
occur from rabid dogs. After a person has been inoculated, the virus enters small nerve
ends around the site of the bite, and slowly travels up the nerve to reach the central
nervous system (CNS) where it reproduces itself, and will then travel down nerves to the
salivary glands and replicate further. The time it takes to do this depends on the
length of the nerve it must travel - a bite on the foot will have a much lengthier
incubation period than a facial bite would. This period may last from two weeks to six
months, and often the original wound will have healed and been forgo
tten by the time symptoms begin to occur.
Symptoms in humans present themselves in one of two forms: 'furious rabies', or 'dumb
rabies'. The former is called such because of the severe nature and range of the
symptoms. The virus, upon reaching the CNS will present the person with headache, fever,
irritability, restlessness and anxiety. Progression may occur on to muscle pains,
excessive salivation, and vomiting. After a few days or up to a week the person may go
through a stage of excitement, and be afflicted with painful muscle spasms which are
sometimes set off by swallowing of saliva or water. Because of this the afflicted will
drool and learn to fear water, which is why rabies in humans was sometimes called
Hydrophobia. The patients are also extremely sensitive to air or drafts blown on their
face. The stage lasts only fews days before the onset of a coma, then death. Dumb
rabies begins similarly to furious rabies, but instead of symptoms progressing to
excitement, a steady retreat and quiet downhill state occurs. This may be accompanied
with paralysis before death. Rabies diagnosis in this type of cases can be missed.
Unfortunately with both furious and dumb rabies, once the disease has taken hold
clinically, rapid and relentless progression to invariable death occurs despite all known
treatments.
Treatment for the recently infected would include washing the wound with soap, detergent,
and water. Then an anti-rabies serum can be administered to humans. Alternative to the
serum, an effective and intensive treatment after infection can be obtained through the
use of a killed virus vaccine, because of the unusually long incubation period. The
vaccine, a Human Diploid Cell Vaccine (HDCV) is grown in human fibroblasts (the
principal nonmotile cells of connective tissue) and is quite safe for human use. When
used, the vaccine did dramatically cut the rabies death toll. Previous killed virus
vaccines, which had been made from infected neural tissue, were not completely effective
at immunisation and had caused adverse side effects.
Since contact with wild animals is the main source of infection for humans and their
pets, avoidance of any direct contact with these animals reduces the risk of being bitten
quite dramatically. Raccoons that are wandering in the daylight hours, or any animal
that seems 'friendly' should be avoided as well. Other high-risk animals include skunks,
foxes, jackals, wolves, as well as an odd association with bats.
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