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Category: Infectious Diseases
Rabies and hydrophobia are two different terms, meaning the
same disease, the former meaning to rage or become mad. This term applies
more especially to the disease as it exists in the maniacal form in the
lower animals, while hydrophobia comes from the Greek, meaning "dread of
water." As we occasionally find this dread of water only in the human
subject, the term is properly used in such a case. The lower animals
frequently attempt to drink water even though the act brings on a
spasmodic contraction of the swallowing (deglutitory) muscles. Hydrophobia
is an acute infectious disease communicated to man by the bite of an
animal suffering from rabies. It is due to a definite specific virus which
is transmitted through the saliva by the bite of a rabid animal. Its
natural habitat (location) is the nervous system, and it does not retain
its virulence when introduced into any other system of organs. It is
essentially a nervous disease and transmitted by the saliva of rabid
animals. When inoculated into a wound this virus must come in contact with
a broken nerve trunk in order to survive and reproduce itself. If by
accident it attacks the end of the broken nerve trunk, it slowly and
gradually extends to the higher nerve centers and eventually produces the
The incubation, or the time it takes for the disease to develop, varies,
but usually is from three to six months. There is a recorded case where
the person began to show symptoms of the disease thirteen days after
having received a severe wound on the head. The incubation period is
seldom longer than six months. The symptoms of the disease in the human
being vary within narrow limits. There are three classic symptoms usually
encountered, and these are fear, apprehension or excitement, together with
deglutitory (swallowing) spasms, terminating in general paralysis. The
patient remains conscious of his agony to the end, but the period of
illness is of short duration, lasting from one to three days.
The bites of rabid dogs cause ninety per cent of the cases in man and
animals. The cat is the next important factor in spreading the disease and
about six per cent of the cases are caused by this animal. For other cases
four per cent come from bites of horses, wolves, foxes, etc. The wolf in
Russia, or other animals like it, may be the chief cause there; but dogs
cause ninety per cent, taking all the cases found. Man, dog, cat, horse,
cattle, sheep, goat, hog, deer, etc., are subject to the disease either
naturally or experimentally. The disease is confined commonly to dogs,
because the dog naturally attacks animals of his own species and thus
keeps the disease limited mainly to his own kind. Naturally the dog
follows this rule, but on the other hand, in the latter stages of the
disease he usually goes to the other extreme and even attacks his own
master, etc. The dogs that are the most dangerous and do the greatest
damage are of the vicious breeds.
The rabbit or guinea pig is used for demonstration in the laboratory.
Guinea pigs respond to the virus more rapidly than do other animals and
therefore they are especially useful in diagnostic work. Rabbits, however,
on account of the convenient size and ease with which they are operated
upon, are usually the choice in the production of material used in
The director of one Pasteur Institute says, "We have two classes of
patients to deal with in the Pasteur institute. The larger class, of
course, are those inoculated by the bite of rabid animals, but we also
have a few who are infected by the rabid saliva accidentally coming in
contact with wounds already produced. In these accidental eases the
disease is almost as likely to result as in those to whom the virus is
directly communicated by the bite." The wounds considered most dangerous
are the recent fresh wounds. The possibility of infection decreases with
the formation of the new connective tissue which protects the ends of the
broken nerve fibres. One must remember, however, that wounds over joints,
especially on the hands, are likely to remain open for some time. A dog
ill of this disease can give the disease to man through licking a wound.
Such a case has been recorded. This dog licked the child's hands before it
was known to be mad. The child died from the disease. As stated before
ninety per cent of the cases are inoculated by the bites of rabid animals.
The wounds are considered according to their severity and location.
Lacerating, tearing wounds upon uncovered surfaces, especially the head,
are the most dangerous. This is due to the fact of the closeness of the
brain and the large amount of infection in such a wound, and for this
reason treatment should be immediately given. But smaller wounds should
also be treated for the smallness of the wound furnishes no sure criterion
as to the future outcome of the disease. All possible infections should be
regarded as dangerous when considering the advisability of taking the
Pasteur Treatment. The small wound has usually a longer period of
incubation, because of the small amount of infection, still it may cause a
fatal termination. A dog never develops rabies from a lack of water or
from being confined or overheated during the summer months. A spontaneous
case of rabies has never been known. It must be transmitted from animal to
animal and the history of the case will point to a previous infection by a
Where rigid quarantine rules exist the disease does not occur. In
Australia they quarantine every dog, that comes to that country, for six
months, and in consequence they have never had a case of rabies. In Russia
they have had many cases. In Constantinople the disease frequently "runs
riot." France has lost as many as 2,500 dogs in one year. Before the
Pasteur Treatment was instituted (in 1885) there was an average of sixty
deaths in human beings in the Paris hospitals.
Belgium and Austria average one thousand dogs annually. There was a yearly
average in Germany of four hundred dogs, dying of rabies, until the law
requiring the muzzling of dogs was strictly enforced and since that time
the disease is practically unknown. We do not have strict quarantine laws
against dogs, and the result is death from hydrophobia in many states
annually. It was formerly believed that rabies was a hot weather disease.
The number of cases during the winter months of late years has disproved
that belief, for the records of the institute for treatment of hydrophobia
at Ann Arbor have shown a decrease of cases during the summer months. This
was before 1908. This shows that rabies is not a hot weather disease.
Ordinarily cases of rabies occur here and there (sporadic), but if the
conditions are favorable epidemics break out. One dog may bite several
dogs and these dogs bite others and thus spread the disease to many. Not
every animal bitten by a mad dog develops the disease. The disease does
not always follow the bite. Only about forty per cent of all animals
bitten by a mad dog contract the disease. This is given by a noted
authority. Statistics also show that in man the disease develops in only
about twenty per cent of the cases in those who have been bitten by rabid
dogs. But in dealing with those who have been bitten such measures should
be taken as would be if they were certain of developing the disease; one
cannot tell how much poison enters the system in such cases and preventive
procedures should be taken. There are reasons why everyone who is bitten
does not contract the disease.
The location and character of the bite must be considered. Bites on the
head, neck and hands have been recognized as more dangerous, from early
times, and such bites produce fatal results quicker than do bites on other
parts of the body, and the reason is largely due to the fact that the
other parts of the body are more or less protected by the clothing, and
this clothing prevents the entrance of so much poison into the system.
Bites on the head give a high mortality rate and are rapidly fatal. The
close proximity to the brain is one reason.
The part the clothing plays in protection is clearly shown by the
following quotation from an eminent authority: "In India where the natives
dress very scantily, the mortality was exceedingly high up to a few years
ago, at which time the British introduced the Pasteur laboratories. The
clothing protects the body and it holds back the saliva and can be looked
upon as a means of filtering the saliva of the rabid animal, most of the
saliva is held back as the teeth pierce the clothing, so that upon
entering the flesh the teeth are practically dry, and only a portion of
the virus is introduced. Upon entering the wound this small amount of
virus is further diluted by the tissue juices to the non-infectious point.
We know from actual experimental work in the laboratory that the higher
dilution will not kill."
If a portion of the brain of an animal dead from street virus is taken and
made up in a dilution of one to five hundred, and this is injected, we
find that it does not produce death. But a dilution of one to three
hundred will invariably kill. This is practically what very often happens
when one is bitten through the clothing. The saliva may be filtered and
held back so that a small amount is introduced; perhaps a dilution of one
to five hundred of the virus may get into the wound, but this is usually
not enough to cause the disease. There is no possible way of estimating
the amount of the inoculation. In such cases one's chances of never
contracting the disease are only decreased; that is all we can say.
The treating of individuals, bitten by rabid animals, in the Pasteur
Institutes, is simply the practical application of results obtained by
Pasteur from his original work on rabies virus. Pasteur was a French
chemist living in Paris, and he began his search for the cause and cure of
rabies in 1880. He hoped to find a sure method of preventing the
development of the dread disease, even if he could not find a cure for it
after it had developed. While he was pursuing this research Pasteur had
access to the cases of rabies in the Paris hospitals, and these numbered
sixty each year. He had practically an unlimited supply, for France could
furnish him with twenty-five hundred more mad dogs, and a large number of
other animals each year.
Pasteur devoted the remainder of his life to the study of this subject. He
collected some saliva from the mouth of a child, on December 11, 1880, who
had died at the Hospital Trousseau four hours before. This saliva he
diluted with distilled water, and this mixture he injected into rabbits,
and they all died, and the saliva taken from these rabbits when injected
into other rabbits caused their death with rabies. He found also that
saliva from rabid dogs almost always caused the disease. The incubation
period varied within wide limits, and very often the animals lived. He
then used the blood of rabid dogs for inoculation, but these blood
inoculations always failed to produce the disease. Pasteur was convinced
after careful study of rabid animals during the many months necessary to
complete his experiments, that rabies was a disease of the nervous system,
and that the poison (virus) was transmitted from the wound to the brain by
the way of the nerve trunks. Then to prove his theory Pasteur removed a
portion of the brain of a dog that had died of rabies. A part of this was
rubbed up in sterile water and used to inoculate other animals; and
subcutaneous inoculations with this material almost always produced death.
After this Pasteur tried a new method and injected directly into the
nervous system, either into the nerve trunk or directly into the brain,
after trephining, and all such injections produced rabies in the injected
animal and death. He also found that rabbits inoculated in the brain
always died in the same length of time. When he injected into the nerve
trunk the inoculation period was longer, depending upon the distance from
the brain. Two problems now remained for Pasteur to solve, and these were,
how could he obtain the definite virulence and how could he reduce the
virulence regularly and gradually, so that it could be used by inoculation
safely as a vaccine to produce immunity to rabies in healthy animals, and
also to prevent the development of rabies in animals bitten by rabid
animals. He first tried successive inoculations. These inoculations were
made, after trephining, directly to the brain, and he used a portion of
the brain as a virus each time. He inoculated rabbit number one with a
portion of brain taken from a rabid dog, and this rabbit died on the
fifteenth day. He then inoculated rabbit number two with a portion of the
brain of rabbit number one; from the brain of rabbit number two the virus
was supplied for inoculating rabbit number three, and thus the brain of
each inoculated rabbit was taken, after its death, for material to
inoculate the next rabbit in the series. This experimentation showed him
that each rabbit in the series died a little sooner, showing that the
virus was becoming more virulent, till no increase in activity of the
poison was shown after the fiftieth successive inoculation. "Rabbits
inoculated with a brain suspension of rabbit number fifty all died in
seven days." This caused Pasteur to name the virus of number fifty "virus
fixe," a virus of definite length. He now had obtained a virus of definite
strength and the next question was, how could the virulence be gradually
and definitely reduced.
This he accomplished after many experiments. He proved that pieces of the
"medulla oblongata" suspended in sterile tubes which contained fragments
of caustic potash, steadily and gradually reduced their virulence as they
dried, till the fourteenth day, when they were practically inert. New
specimens were prepared each day and cords which had dried in one day
Pasteur called "one-day virus;" cords which had dried in two days, "two
day's virus," and so on up to the fourteenth day. With this graduated
virus he now experimented on dogs, and the injection he used on the first
day consisted of an emulsion of fourteen-day virus; for the second day,
the thirteen-day virus, thus using a stronger virus each day, until on the
fourteenth day he used the full strength virus. This treatment produced
what is called immunity in the dog, and even the direct inoculation into
the brain of the strong virus would not produce death.
After Pasteur had thoroughly satisfied himself by repeated trials, he
announced his wonderful discovery, and it was in 1886 that Pasteur
considered the preventive inoculation in human beings as resting upon a
satisfactory experimental basis. During these five years this eminent man
proved that it was possible to protect or immunize the lower animals,
rabbits and dogs, against inoculation with the virulent virus.
The efficiency of this immunity was given trials by different methods of
inoculation. It was found that sixty per cent of dogs inoculated under the
"dura" (a membrane of the brain) were saved if treatment was given the
second day. This test is more severe than is required to meet the ordinary
infection of rabies. Pasteur, after a series of these final tests were so
convincing, prescribed the preventive inoculations in human beings and on
July 6th, 1886, the first human patient received the first treatment of
his series of inoculations.
The method of obtaining the attenuated virus used in the treatment is as
follows: A rabbit is inoculated by the brain method before described, each
day, with suspension of the fresh, fixed virus. These rabbits die in six
days after the inoculation. In this way a rabbit dies each day; the spinal
cord is removed, divided into sections, and suspended in a flask
containing potassium hydrate. The action of potassium hydrate is drying
(desiccating). A series of these cords, which have been hung on fourteen
successive days, are always kept in stock for the treatment of patients.
The virus becomes less active with each successive day of exposure to
drying (desiccation) and finally the virulence is altogether lost.
When the patient comes for treatment the fourteenth and thirteenth-day
cords are used for the first inoculation, and on each successive day the
patient receives inoculation, the strength of which has been regulated by
the number of days the cord has been hanging. During the first four days
patients receive injections of six cubic centimeters of emulsions made
from cords aging from fourteen to seven days, and from the fifth day until
the completion of the course of treatment patients receive emulsions from
cords of higher immunizing properties, but no cords desiccated for less
than four days are used.
Death rate from 1878-1883 before Pasteur treatment was instituted taken
from documents in the department of the Seine:
1878 143 bitten. 24 deaths.
1879 76 " 12 "
1880 68 " 5 "
1881 156 " 22 "
1882 67 " 11 "
1883 45 " 6 "
Average of one death to every six bitten, or seventeen per cent mortality.
Incubation period from eleven days to thirteen months, average one hundred
and twenty days, depending upon location of bite. Pasteur Institute
records during the years 1886-1887 and first half of 1888, show that
Pasteur had under his supervision 5,374 persons bitten by animals either
proven or thought to have been mad. Mortality for 1886 was 1-34 per cent,
during 1887 it was 1-12 per cent, during 1888 it was 77/100 per cent. With
the later treatment the mortality has decreased to 3-10 per cent in 1908.
The Pasteur method of treatment is a process of immunization which must be
completed before the development of the disease. It is of no value after
the symptoms have appeared.
Those who have not been affected can be immunized the same as those who
have been bitten. The individual who has been bitten by a mad dog realizes
when and how severely he has been bitten, and were it not for the
so-called period of latent development of the virus, it would not be
possible to carry out the Pasteur treatment. The patient may, if he will,
take advantage of this fact and be immunized by treatment before the
disease has developed. Deep and severe bites are most dangerous, but the
disease may develop simply from a rabid dog licking a scratch of the skin.
As before stated bites on exposed or uncovered surfaces, are more
dangerous than those through clothing. There is a very easy access of the
saliva to the wound in the unprotected part, while in the protected parts
the teeth in passing through the protection, clothing, are freed of their
saliva at least partially. The virus is conveyed from the bitten part or
inoculation to the central nervous system through the nerve trunk, and the
rapidity of extension depends upon the resistant powers of the patient,
the virulence and the amount of virus deposited in the bitten part at the
time the person was bitten. This disease develops only in nerve tissues.
Virus can be found in the nerves of the side bitten, while the
corresponding nerves on the opposite side are free from it. It can be
ascertained that the virus is present in the medulla oblongata before the
lower portion of the cord.
Comparative danger. A wound of the hand after a delay of three weeks is
as dangerous as a bite on the head exposed only a few days. There is
always a possibility of an accumulative action and extension of the virus
along the nerve trunk to the central nervous system during the interval of
exposure, and this should be always borne in mind. It is stated by
authority that the virus is not transmitted by the bite of a rabid animal
until two days previous to the appearance of the first symptoms. It is
with some difficulty that a decision is reached in advising patients who
are bitten to take treatment early in the course of the disease. The
symptoms are often so very obscure and slight that they are not
recognized. If a dog which is not naturally vicious suddenly bites without
any cause it should be tied securely and watched for seven days; and
should it develop symptoms of the disease during this period the bite
should be considered dangerous.
Immediate treatment of the wound. A temporary measure is the
cauterization of the wound; do not neglect this because a few hours have
passed since the person was bitten, for wounds may be cauterized with
advantage even after two or three days have elapsed. Of course the earlier
it is done the better. If they are thoroughly laid open and scrubbed it is
more effective. Nitric acid used freely is the best method to use. Wash
the wound freely with boiled water after the acid has been applied;
ninety-five per cent carbolic acid may be used if nitric acid cannot be
If carbolic acid is used it is necessary that it be washed from the wound
by the free use of absolute alcohol, followed by boiled water and a
dressing of bichloride of 1-7000. This prevents the ulceration of the
wound by the carbolic acid. Cauterization thoroughly done destroys a part
of the inoculated virus. Thorough cauterization is especially necessary
with large wounds in which large quantities of the virus is inoculated.
When to send patients to an Institute. Send them immediately, if there is
good reason to believe the animal had rabies. It is not wise to wait until
the animal dies; it is very important that treatment is begun as soon as
possible, especially in severe bites.
What to send for examination. The entire head may be sent by express, or
better, the health officer should bring it in person. This saves time and
relieves anxiety; or a portion of the brain may be removed under
thoroughly clean conditions and placed in a sterilized twenty per cent
solution of glycerin and water. In this way the virus retains its
virulence and putrefaction is diminished. The first method is the best,
taking the head directly. The head after it reaches the laboratory is
examined microscopically for "negri bodies," and if there is no
contamination the microscopic findings are verified by animal
inoculations. The presence of negri bodies in a specimen is of great value
owing to the rapidity with which a diagnosis can be made. In one case a
positive diagnosis was reported within twenty minutes after the specimen
entered the laboratory and within the next hour and a half the patient
bitten by the dog the same day had begun her course of protective
injections and was saved.
Protection. To stamp out this disease city authorities, etc., can enact
laws. All ownerless dogs should be killed, and the keeping of useless dogs
should be discouraged by taxation. All dogs should be thoroughly muzzled
where the disease prevails. This article is made up from an article
written by an acknowledged authority on this disease, a man in charge of a
Cities where Pasteur Institutes are located:
Ann Arbor, Michigan. Baltimore, Maryland.
Chicago, Illinois. Austin, Texas.
Minnesota. Toronto, Ont.
New York City.
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