connection with the disease was made by Louis Pasteur in 1881, and
consisted in the new principle of producing immunity by the inoculation of
weakened cultures of the bacillus causing the disease. This method has been
quite extensively adopted in France, and to some extent in other European
countries, and in the United States. The fluid used for inoculation
consists of bouillon in which modified anthrax bacilli have multiplied and
are present in large numbers. The bacilli have been modified by heat so
that to a certain degree they have lost their original virulence. Two
vaccines are prepared. The first or weaker, for the first inoculation, is
obtained by subjecting the bacilli to the attenuating effects of heat for a
longer period of time than in the case of the second, or stronger vaccine,
for a second inoculation some 12 days later.
There are several difficulties inherent in the practical application of
Pasteur's vaccine. Among them may be mentioned the variable degree of
attenuation of different tubes of the vaccine and the varying
susceptibility of the animals to be inoculated. The use of this vaccine is
increasing, nevertheless, and has reduced the mortality in the affected
districts from an average of 10 per cent in the case of sheep, to less than
1 per cent, and from 5 per cent with cattle, to less than one-half of 1 per
cent.
It is very important to call attention to the possibility of distributing
anthrax by this method of protective inoculation, as the bacilli themselves
are present in the culture liquid. It is true that they have been modified
and weakened by the process adopted by Pasteur, but it is not impossible
for such modified virus to regain its original virulence after it has been
scattered broadcast by the inoculation of large herds. It is obviously
unsafe to have such vaccine injected by a layman; instead, it should be
handled only by a competent veterinarian.
There are other disadvantages in this method of vaccination, and they all
must be given due consideration. The unstable keeping quality of the
Pasteur vaccine is a very important factor to be considered. Experience in
this line has proved that Pasteur vaccine may deteriorate within a very
short time after its preparation, and in repeated instances it has proved
inert within three months of its preparation. When exposed to warm
temperature and light, it deteriorates very rapidly; and when it is
considered that the products of manufacturers may be stored under
unfavorable conditions in branch houses and on the shelves of rural drug
stores, the loss of potency can be readily explained. These deficiencies
have been recognized by many investigators, and because of the superior
keeping qualities particular attention has been directed toward the
preparation of a spore vaccine by Zenkowsky of Russia, Detre of Hungary,
and Nitta of Japan. For the purpose of producing a spore vaccine it is
desirable to use a peptone-free agar medium, and after inoculation with an
attenuated culture of the anthrax bacillus, it is allowed to grow at a
temperature of 37∞ C. for 4 to 7 days. By this time an abundance of spores
will have formed. The growth is then collected in sterile flasks and heated
to a temperature of 60∞ C. for one-half hour to destroy the vegetative
forms of the organism. If it is desired to use for vaccination one million
spores, it is advisable to dilute the vaccine to a quantity of which 1
cubic centimeter would contain this number. Of such a vaccine 1 cubic
centimeter would constitute the dose for cattle and horses. In all forms of
vaccination against anthrax in sheep the greatest care must be exercised,
as these animals are very susceptible to the disease, and at times vaccines
which have no ill effects on cattle will prove fatal to sheep. Therefore
the dose of the spore vaccine for sheep should not be more than one-fourth
of that given to cattle.
Sclavo, Sobernheim, and others have established that injections of
increasing quantities of virulent cultures into immune animals produced a
serum which has great protective value against anthrax. Such protective
serum may be produced in the various susceptible animals.
For immunization purposes it is advisable to use the simultaneous method;
that is, both the spore vaccine and the anthrax serum should be injected.
It is desirable to divide the herd to be treated into groups of ten or
twelve and inject, first, each animal of the group with the serum,
following this with the injection of the spore vaccine. The serum should be
injected on one side, either on the neck or back of the shoulder, and the
spore vaccine on the other side, injections being made subcutaneously. In
herds in which the disease has already made its appearance it is necessary
to take the temperatures of all the animals and to subject to the
simultaneous vaccination only those that show no rise in temperature. All
others should be given the serum-alone treatment in doses varying in
accordance with the severity of the symptoms manifested by the individual
animals. If the examination reveals a considerable number of infections, it
is advisable to use the serum alone for all the animals, and in three or
four weeks to revaccinate by the simultaneous method. The dosage should
depend on the potency of the serum, serum of a high potency naturally being
most desirable. Thus serum in 10 cubic centimeter doses for large animals,
and 3 to 5 cubic centimeter doses for smaller ones, has been found to be
effective in producing a temporary immunity.
As anthrax is entirely different from blackleg, vaccine for the latter does
not act as a preventive against the former.
ANTHRAX IN MAN (MALIGNANT PUSTULE, OR CARBUNCLE).
Anthrax may be transmitted to man in handling the carcasses and hides of
animals which have succumbed to the disease. The infection usually takes
place through some abrasion or slight wound of the skin into which the
anthrax spores, or bacilli, find their way. The point of inoculation
appears at first as a dark point or patch, compared by some writers to the
sting of a flea. After a few hours this is changed into a reddened pimple,
which bears on its summit, usually around a hair, a yellowish blister, or
vesicle, which later on becomes red or bluish in color. The burning
sensation in this stage is very great. Later this pimple enlarges, its
center becomes dry, gangrenous, and is surrounded by an elevated,
discolored swelling. The center becomes drier and more leatherlike, and
sinks in as the whole increases in size. The skin around this swelling or
carbuncle is stained yellow or bluish, and is not infrequently swollen and
doughy to the touch. The carbuncle itself rarely grows larger than a pea or
a small nut, and is but slightly painful.
Anthrax swellings or edemas, already described as occurring in cattle, may
also be found in man, and they are at times so extensive as to produce
distortion in the appearance of the part of the body on which they are
found. The color of the skin over these swellings varies according to the
situation and thickness of the skin and the stage of the disease, and may
be white, red, bluish, or blackish.
As sooner or later these carbuncles and swellings may lead to an infection
of the entire body, and thus be fatal, surgical assistance should at once
be called if there is well-grounded suspicion that any swellings resembling
those described above have been caused by inoculation with anthrax virus.
Inasmuch as physicians differ as to medicinal treatment of such accidents
in man, it would be out of place to make any suggestions in this
connection.
Extensive data are available, however, on the effectiveness of anthrax
serum for the treatment of the disease in man. It is recommended that from
30 to 40 cubic centimeters of serum be injected in three or four different
places. Should no improvement follow in 24 hours additional injections of
20 to 30 cubic centimeters should be administered.
In most instances the results are favorable, and this treatment is
acknowledged to be superior to any other mode of treatment known for the
disease.
To show that the transmission of anthrax to man is not so very uncommon, we
take the following figures from the 1890 report of the German Government:
The attention of the authorities was brought to 111 cases, of which 11
terminated fatally. The largest number of inoculations were caused by the
slaughtering, opening, and skinning of animals affected with anthrax;
hence, the butchers suffered most extensively. Of the 111 thus affected, 36
belonged to this craft. Infected shaving brushes also are very dangerous.
In addition to anthrax of the skin (known as malignant pustule), human
beings are subject, though very rarely, to the disease of the lungs and the
digestive organs. In the former case the spores are inhaled by workmen in
establishments in which wool, hides, and rags are worked over, and it is
therefore known as woolsorter's disease. In the latter case the disease is
contracted by eating the flesh of diseased animals which has not been
thoroughly cooked. These forms of the disease are more fatal than those in
which the disease starts from the skin.
BLACKLEG.
[Pl. XLII.]
Blackleg, black quarter, quarter ill, symptomatic anthrax, charbon
symptomatique of the French, Rauschbrand of the Germans, is a rapidly
fatal, infectious disease of young cattle, associated with external
swellings which emit a crackling sound when handled. This disease was
formerly regarded identical with anthrax, but investigations by various
scientists in recent times have definitely proved the entire dissimilarity
of the two affections, both from a clinical and a causal standpoint. The
disease is produced by a specific bacillus, readily distinguishable from
that causing anthrax. (Pl. XXVIII, fig. 4.) Cattle between 6 months and 2
years of age are the most susceptible. Sucking calves under 6 months are
rarely attacked, nor are they so susceptible to inoculation as older
animals. Cattle more than 2 years of age may become affected, but such
cases are infrequent. Sheep and goats may also contract the disease, but
man, horses, hogs, dogs, cats, and fowls appear to be immune.
Like anthrax, blackleg is more or less restricted to definite localities.
There are certain pastures upon which the disease regularly appears in the
summer and fall of the year. As to any peculiarities of the soil nothing is
definitely known. Some authors are inclined to regard moist, undrained, and
swampy pastures favorable to this disease, but these theories will hardly
hold, as it is found in all kinds of soil, in all altitudes, at all seasons
of the year, and under various climatic conditions. It occurs in this
country from the Atlantic to the Pacific and from Mexico to Canada, but it
is more prevalent in the Western and Southwestern States. In Europe it
exists in France, various parts of Germany, in Belgium, Norway, Denmark,
Italy, and in the Alps of Switzerland. In Africa it occurs in Algeria and
to some extent in Natal and bordering countries. In South America it
prevails quite extensively throughout Argentina. Cattle in Cuba and
Australia also suffer.
_Cause._--The cause of the disease is a bacillus resembling in some minor
respects the anthrax bacillus and differing but little from it in size. It
also possesses the power of forming within itself a spore. In Plate XXVIII,
figure 4, this is represented as an uncolored spot located in one end of
the rod, which is enlarged so that the rod itself appears more or less
club-shaped. What has already been stated concerning the significance of
the spore of the anthrax bacillus applies equally well to these bodies.
They resist destructive agents for a considerable time, and may still
produce disease when inoculated after several years of drying. This fact
may account for the occasional appearance of blackleg in stables. In order
to meet the requirements for the development of the spores, which takes
place only in the absence of the atmosphere, it is necessary that the wound
be very small and deep enough to penetrate the subcutaneous tissue.
Several observers have found this organism in the mud of swamps. By placing
a little of the mud under the skin, the disease has been produced.
Since the disease may be produced by placing under the skin material
containing the specific bacilli and spores, it has been assumed that cattle
contract the disease through wounds, principally of the skin, or very
rarely of the mouth, tongue, and throat. Slight wounds into which the virus
may find access may be caused by barbed wire, stubbles, thorns, briers,
grass burs, and sharp or pointed parts of feed. Infection by way of
digestive tract is also probable.
_Symptoms and lesions._--The symptoms of blackleg may be either of a
general or of a local nature, though more frequently of the latter. The
general symptoms are very much like those belonging to other acute
infectious or bacterial diseases. They begin, from one to three days after
the infection has taken place, with loss of appetite and of rumination,
with dullness and debility, and a high fever. The temperature may rise to
107∞ F. To these may be added lameness or stiffness of one or more limbs,
due to the tumor or swelling quite invariably accompanying the disease.
After a period of disease lasting from one to three days the affected
animal almost always succumbs. Death is preceded by increasing weakness,
difficult breathing, and occasional attacks of violent convulsions.
The most important characteristic of this disease is the appearance of a
tumor or swelling under the skin a few hours after the setting in of the
constitutional symptoms described above. In some cases it may appear first.
This tumor may be on the thighs (hence "blackleg," "black quarter"), the
neck, the shoulder, the breast, the flanks, or the rump; never below the
carpal (or knee) and the hock joint. It more rarely appears in the throat
and at the base of the tongue. The tumor, at first small and painful,
spreads very rapidly both in depth and extent. When it is stroked or
handled a peculiar crackling sound is heard under the skin; this is due to
a collection of gas formed by the bacilli as they multiply. At this stage
the skin becomes dry, parchment-like, and cool to the touch in the center
of the tumor. If the swelling is cut into, a frothy, dark-red, rather
disagreeable-smelling fluid is discharged. The animal manifests little or
no pain during the operation.
As it is frequently desirable to know whether the disease is anthrax or
blackleg, a few of the most obvious post-mortem changes may here be cited.
The characteristic tumor with its crackling sound when stroked has already
been described. If after the death of the animal it is more thoroughly
examined, it will be noted that the tissues under the skin are infiltrated
with blood and yellowish, jellylike material and gas bubbles. The
muscular tissue beneath the swelling may be brownish or black, shading into
dark red. (Pl. XLII.) It is soft, easily torn and broken up. The muscle
tissue is distended with numerous smaller or larger gas-filled cavities,
often to such extent as to produce a resemblance to lung tissue. Upon
incision it does not collapse perceptibly, as the gas cavities are not
connected with one another.
In the abdomen and the thorax bloodstained fluid is not infrequently found,
together with bloodstaining of the lining membrane of these cavities. Blood
spots (or ecchymoses) are also found on the heart and lungs. The liver is
congested, but the spleen is always normal in appearance.
_Differential diagnosis._--Among the features of this disease which
distinguish it from anthrax may be mentioned the unchanged spleen and the
ready clotting of the blood. It will be remembered that in anthrax the
spleen (milt) is very much enlarged, the blood tarry, coagulating feebly.
The anthrax carbuncles and swellings differ from the blackleg swellings in
not containing gas, in being hard and solid, and in causing death less
rapidly.
It is difficult to distinguish between the swellings of blackleg and
malignant edema, as they resemble each other very closely and both are
distended with gas. Malignant edema, however, generally starts from a wound
of considerable size; it usually follows surgical operations, and seldom
results from the small abrasions and pricks to which animals are subjected
in pastures. Inoculation experiments on guinea pigs, rabbits, and chickens
will generally disclose the differences between the three diseases above,
as all these species are killed by the germ of malignant edema, only the
first two species by the anthrax bacillus, while the guinea pigs alone will
succumb to the blackleg infection. Hemorrhagic septicemia may be
differentiated from blackleg by its affecting cattle of all ages, by the
location of the swelling usually about the region of the throat, neck, and
dewlap, by the soft, doughy character of the swellings without the presence
of gas bubbles, and finally by the characteristic hemorrhages widely
distributed throughout the body. Other means of diagnosis, which have
reference to the specific bacilli, to the inoculable character of the virus
upon small animals, and which are of decisive and final importance, can be
utilized only by the trained bacteriologist and veterinarian.
_Treatment._--In this disease remedies have thus far proved unavailing.
Some writers recommend the use of certain drugs, which seem to have been
beneficial in a few cases, but a thorough trial has shown them to be
valueless. Others advise that the swelling be opened by deep and long
incisions and a strong disinfectant, such as a 5 per cent solution of
carbolic acid, applied to the exposed parts; but this procedure can not be
too strongly condemned. As nearly all those attacked die, in spite of every
kind of treatment, and in view of the fact that when these tumors are
opened the germs of the disease are scattered over the stables or pastures,
thus becoming a source of danger to other cattle, it is obvious that such
measures do more harm than good and should be put aside as dangerous.
Bleeding, nerving, roweling, or setoning have likewise some adherents, but
the evidence indicates that they have neither curative nor preventive value
and therefore should be discarded for the method of vaccination which has
been thoroughly tried and proved to be efficacious.
_Prevention._--The various means suggested under "Anthrax" to prevent the
spread or recurrence of this disease are equally applicable to blackleg,
and hence do not need to be repeated here in full. They consist in the
removal of well animals from the infected pasture to a noninfected field,
the draining of the swampy ground, the burial or burning of the carcasses
to prevent the dissemination of the germs over vast areas through the
agency of dogs, wolves, buzzards, or crows, the disinfection of the stables
and the ground where the animals lay at the time of death, and, if
possible, the destruction of the germs on the infected pastures. One of the
most effective methods for freeing an infected pasture from blackleg is to
allow the grass to grow high, and when sufficiently dry to burn it off. One
burning off is not sufficient to redeem an infected pasture, but the
process should be repeated several years in succession. This method,
however, is in many instances impracticable, as few cattle owners can
afford to do it, and the only means left for the protection of the animals
is vaccination.
_Immunization by vaccination._--Three French veterinarians, Arloing,
Cornevin, and Thomas, were the first to discover that cattle may be
protected against blackleg by inoculation with virulent material obtained
from animals which have died of this disease. Later they devised a method
of inoculation with the attenuated or weakened blackleg spores which
produced immunity from natural or artificial inoculation of virulent
blackleg germs. Their method has undergone various modifications both in
regard to the manufacture of the vaccine and in the mode of its
application. Kitt, a German scientist, modified the method so that but one
inoculation of the vaccine was required instead of two, as was the case
with that made by the French investigators. The vaccine formerly prepared
and distributed by the Bureau of Animal Industry combined the principle of
Arloing, Cornevin, and Thomas, and the modification of Kitt.
By vaccination we understand the injection of a minute amount of
attenuated--that is, artificially weakened--blackleg virus into the system.
This virus is obtained from animals which have died from blackleg, by
securing the affected muscles, cutting them into strips, and drying them in
the air. When they are perfectly dry they are pulverized and mixed with
water to form a paste, smeared in a thin layer on flat dishes, placed in an
oven, and heated for six hours at a temperature close to that of boiling
water. The paste is then transformed into a hard crust, which is pulverized
and sifted and distributed in packages containing either 10 or 25 doses.
This constitutes the vaccine, the strength of which is thoroughly tested on
experiment animals before it is distributed among the cattle owners. This
vaccine, which is in the form of a brownish, dry powder, is mixed with
definite quantities of sterile water, filtered, and by means of a
hypodermic syringe the filtrate injected under the skin in front of the
shoulder of the animal. The inoculation is usually followed by
insignificant symptoms. In a few cases there is a slight rise of
temperature, and by close observation a minute swelling may be noted at the
point of inoculation. The immunity conferred in this way may last for 18
months, but animals vaccinated before they are 6 months old and those in
badly infected districts should be revaccinated before the following
blackleg season.
The effect of the vaccine prepared by this bureau in preventing outbreaks
of the disease and in immediately abating outbreaks already in progress was
highly satisfactory, and it is not to be doubted that thousands of young
cattle were saved to the stock owners during the 25 years in which the
vaccine was distributed.[6] More than 47,000,000 doses were sent out during
this period, and from reports received it is safe to conclude that more
than 40,000,000 were actually injected, whereby the percentage of loss from
blackleg has been reduced from 10 per cent, which annually occurred before
using, to less than one-half of 1 per cent per annum. With these figures
before us it is plain that the general introduction of preventive
vaccination must be of material benefit to the cattle raisers in the
infected districts. Moreover, there is every reason to believe that with
the continued use of blackleg vaccine in all districts where the disease is
known to occur, and an earnest effort on the part of the stock owners to
prevent the reinfection of their pastures by following the directions
given, blackleg may be kept in check and gradually eradicated.
Immunization against blackleg is now frequently accomplished by the use of
the so-called blackleg aggressin and blackleg filtrates.
NECROTIC STOMATITIS (CALF DIPHTHERIA).
[Pl. XLIII.]
Necrotic stomatitis is an acute, specific, highly contagious inflammation
of the mouth occurring in young cattle, and characterized locally by the
formation of ulcers and caseo-necrotic patches and by constitutional
symptoms, chiefly toxic.
This disease has also been termed calf diphtheria, gangrenous stomatitis,
ulcerative stomatitis, malignant stomatitis, tubercular stomatitis, and
diphtheritic patches of the oral mucous membrane.