|
Rabies
Rabies is an age-old scourge
which has been recognized as a dread
disease since ancient times. Though it is primarily a disease of the
dog, many other species, including man, are susceptible to infection.
It has been reported in the cat, cow, horse, mule, sheep, goat, hog,
wolf, fox, coyote, hyena, skunk, monkey, deer, antelope, camel, bear,
elk, polecat, bat, squirrel, hare, rabbit, rat, mouse, jackal, marmot,
woodchuck, porcupine, weasel, hedgehog, gopher, raccoon, owl, hawk,
chicken, pigeon, and stork. It is fairly common throughout the world,
though Great Britain, Denmark, Norway, and Sweden have been free from
it for several decades and it has not been reported in Australia.
Rabies may occur in the furious and the dumb forms. In the furious
form, the dog usually first shows a marked change in disposition. Later
the animal has a tendency to wander, and may return home exhausted
after a day or two. The animal seems to become vicious and has an
abnormal tendency to bite. This is because, at this time, the animal
suffers impairment of vision, and, because of fear of its
surroundings, the animal will bite at anything in reach that crosses
its line of vision. As the disease progresses the animal develops a
peculiar hoarseness of voice, shows signs of staggering, paralysis of
the lower jaw, partial paralysis of the limbs, excitability,
convulsions, and finally complete paralysis and death.
In the dumb form, there may simply be a marked depression and then
death, but more commonly the main symptom is paralysis of the lower
jaw. The animal may or may not show a change in
disposition, has no tendency to roam or bite, and is not excitable. The
dropped-jaw appearance often arouses the erroneous contention that a
foreign body might be lodged in the throat. Since the saliva carries
the rabies virus, caution should always be used in approaching the
mouth of an animal that presents such a symptom. The animal eventually
develops complete paralysis and dies. In both furious and dumb rabies
in dogs, once the symptoms appear the animal usually dies within three
to seven days. The disease has been presented here in its most typical
forms. It may occur in many atypical forms, which means that one must
always be aware of its possibility.
The term "hydrophobia," commonly associated with this disease, is a
misnomer. The affected animal has no fear of water as the word implies.
It simply cannot drink because of the paralysis of the lower jaw and
the swallowing mechanism. The term may have its origin in the fact that
humans with rabies develop convulsions due to unsuccessful efforts to
drink, and later even the thought of drinking water may bring on
convulsions. Thus a dread of drinking water becomes established in
many human patients.
Rabies is caused by a filterable virus, is positively diagnosed by the
demonstration of certain structures called Negri bodies on microscopic
examination of brain tissue, and is transmitted mainly by the bite of
rabid dogs, though it has been transmitted experimentally by the
feeding of the meat and milk of rabid animals. Rabies is invariably
fatal in dogs and man when untreated. In dogs, the disease may be
prevented by vaccination, a single vaccination confering immunity for
one year. A newer vaccine is claimed to give protection for at least
three years. As a precautionary measure, all bite cases should be
reported to the local Board of Health, and the animals involved should
be examined to determine whether they have the disease.
|
