by the veterinarians of the eighteenth century. It received its first
important notice from the great Jenner, who confounded it with grease in
horses, since animals with this disease are very liable to have the
eruption of variola appear on the fetlocks. He saw these cases transmit
the disease to cattle in the byres and to the stablemen and milkmaids
who attended them, and furnish the latter with immunity from smallpox,
which led to the discovery of vaccination. Horsepox is also frequently
mistaken for the exanthemata attending some forms of venereal disease in
horses.
Variola in the horse, while it is identical in principle, general
course, complications, and lesions with variola in other animals, is a
disease of the horse itself, and is not transmissible in the form of
variola to any other animal; nor is the variola of any other animal
transmissible to the horse. Cattle and men, if inoculated from a case of
horsepox, develop vaccinia, but vaccinia from the latter animals is not
so readily reinoculated into the horse with success. If it does develop,
it produces the original disease.
_Causes._--The direct cause of horsepox is infection. A large number of
predisposing causes favor the development of the disease, as in the case
of strangles, and this trouble, like almost all contagious diseases,
renders the animal which has had one attack immune. The chief
predisposing cause is youthfulness. Old horses which have not been
affected are less liable to become infected when exposed than younger
ones. The exposure incident to shipment, through public stables, cars,
etc., acts as a predisposing cause, as in the other infectious diseases.
The period of final dentition is a time which renders it peculiarly
susceptible.
Dupaul states that the infection is transmissible through the atmosphere
for several hundred yards. The more common means of contagion is by
direct contact or by means of fomites. Feed boxes and bridles previously
used by horses affected with variola are probably the most frequent
carriers of the virus, and we find the lesions in the majority of cases
developed in the neighborhood of the lips and nostrils. Coition is a
frequent cause. A stallion suffering from this disease may be the cause
of a considerable epizootic, as he transmits it to a number of brood
mares and they in turn return to the farms where they are surrounded by
young animals to which they convey the contagion. The saddle and croup
straps are frequent agents of infection. The presence of a wound greatly
favors the inoculation of the disease, which is also sometimes carried
by surgical instruments or sponges. Trasbot recites a case in which a
set of hobbles, which had been used on an animal suffering from
variola, were used on a horse for a quittor operation and transmitted
the disease, which developed on the edges of the wound.
_Symptoms._--There is a period of incubation, after an animal has been
exposed, of from five to eight days, during which there is no
appreciable alteration in the health. This period is shorter in summer
than in winter. At the end of this time small nodes develop at the point
of inoculation and the animal becomes feverish. The horse is dull and
dejected, loses its appetite, and has a rough, dry coat with the hairs
on end. There is moderate thirst. The respirations are somewhat
quickened and the pulse becomes rapid and full. The body temperature is
elevated, frequently reaching 104 deg. or 105 deg. F. within 36 or 48 hours from
the appearance of the first symptoms.
The visible mucous membranes, especially the conjunctivae, are of a
bright rosy red. In the lymphatic, cold-blooded, and more common horses
these symptoms of fever are less marked; even with a comparatively high
temperature the animal may retain its appetite and work comparatively
well, but these cases, if worked and overheated, are liable to develop
serious complications.
At the end of from three and a half to four days the eruption breaks
out, the fever abates, and the general symptoms improve. The eruption in
severe cases may be generalized; it may be confined to the softer skin
of the nose and lips, the genital organs, and the inside of the thighs,
or it may be localized in the neighborhood of a wound or in the
irritated skin of a pair of greasy heels. It consists of a varying
number of little nodes which, on a mucous membrane, as in the nostrils
or vagina, or on soft, unpigmented skin, appear red and feel at first
like shot under the epidermis. These nodes soften and show a yellowish
spot in the center when they become pustules. The epidermis is dissolved
and the matter escapes as a viscid fluid at first citrine and later
cloudy and purulent, which dries rapidly, forming scabs; if these fall
off or are removed they leave a little shallow, concave ulcer which
heals in the course of five or six days. In the softer skin if pigmented
the cicatrices are white and frequently remain so for about a year, when
the pigment returns. The lips or genital organs of a colored horse, if
covered with a number of small white spots about the size of a pea, will
usually indicate that the animal has been affected with the horsepox.
At times the pustules may become confluent and produce large,
superficial, serpentine ulcers on the membrane of the nostrils, around
the lips or eyelids, or on the borders of wounds and in greasy heels; in
this case the part becomes swollen, hot, painful, and is covered with a
profuse discharge of matter. In this form there is frequently a
secondary fever lasting for a day or two.
In severe cases there may be a suppurative adenitis, or inflammation of
the lymphatic glands which are fed from the affected part. If the
eruption is around the nostrils and lips, the glands between the jaws
(submaxillary) form abscesses as in a case of strangles; if the eruption
is in a pair of greasy heels abscesses may form in the fold of the groin
(inguinal). There may be so much tumefaction of the nostrils as to
produce difficulty in breathing.
_Complications._--A case of horsepox may be attended with various
complications of varying degrees of importance. Adenitis, or suppuration
of the glands, has just been mentioned. Confluent eruptions irritate the
part and induce the animal to rub the inflamed part against the manger
or scratch it in other ways and thus produce troublesome ulcers, which
may leave ugly scars. Irritation of the mucous membrane of the nose
causes severe coryza with purulent discharge.
The eruption may occur in the throat or in the air tubes to the lungs,
developing an acute laryngitis or bronchitis. If the animal is exposed
to cold, or worked so as to engorge the lungs with blood at the
termination of the specific fever, just when the eruption is about to
localize, it may be determined to the lungs. In this case we have a
short, dry cough, labored breathing, the development of a secondary
fever of some gravity, and all the external symptoms of a pneumonia.
This pneumonia differs, however, from an ordinary pneumonia in the
symptoms furnished by the examination of the lungs themselves. In place
of a large mass of the lung tissue being affected the inflammation is
disseminated in smaller spots over the entire lung.
_Diagnosis._--The diagnosis of horsepox is to be based on the presence
of a continuous fever, with rosy mucous membranes, for several days and
the appearance of the characteristic eruption. If the eruption is in the
nasal cavities, marked by a considerable discharge and attended with
submaxillary abscesses, it may be confounded with strangles. If the
throat is affected, it may be confounded with an angina (laryngitis or
pharyngitis), but in the latter the local trouble precedes or is
concomitant with the fever, while in the former the fever precedes the
local trouble by several days. Variola may be confounded with bronchitis
or pneumonia if complicated with these troubles and the eruption is
absent from the exterior, but it is of little moment, as the treatment
for both is much the same. When the eruption is in the neighborhood of
the genital organs the disease has been mistaken for dourine. In variola
the eruption is a temporary one; the nodes and pustules are followed by
shallow ulcers and rapid cicatrization unless continued in the vagina or
on the penis by the rubbing of the walls and filth which accumulates;
there are apt to be pustules at other parts of the body. In the venereal
disease the local trouble commences as a papule and breaks into an
ulcer without having formed a pustule. The ulcer has not the convex rosy
appearance of that of the less serious discharge; the symptoms last for
a longer period, by which time others aid in differentiating the two. In
glanders the tubercle is hard and, after breaking into an ulcer, the
indurated bottom remains, grayish or dirty white in color, ragged, and
exuding a viscous, oily discharge. There is no disposition to
suppuration of the neighboring glands. In variola the rosy shallow ulcer
and healthy pus, with the acutely tumefied glands, should not be
mistaken, at least after a day. I have seen in mules acute glanders
which required a day's delay to differentiate from strangles; at that
time the farcy buds appeared.
_Prognosis._--The average case of horsepox runs a course of dejection,
loss of appetite, and more or less fever for about four days, followed
by a rapid convalescence, and leaves the animal as well and as sound as
before. If the eruption has been excessive or confluent, the ulcerations
may act as irritants and render the animal unfit for use for several
weeks. Laryngitis, pharyngitis, bronchitis, and pneumonia in this
disease are not of greater gravity than they are when occurring from
other causes. The spots denuded of pigment left by the pustules on the
lips and genitals may temporarily depreciate the value of the animal to
a slight degree.
_Treatment._--As this is a disease unattended by alterations of the
blood itself, although a specific fever, and is of a sthenic type,
active remedies are admissible and indicated. The horse should be placed
on a low diet (little or no oats)--bran mashes, a moderate quantity of
good, sound hay, a few carrots or apples, which will act as laxatives;
also slop feed. Barley flour is more cooling for mashes than bran or
oatmeal. Water may be given as the animal desires it, but it should not
be cold; if a half bucketful of water is kept in the manger, the horse
will take but a few swallows at a time. One-dram doses of nitrate of
potash or 1-ounce doses of sweet spirits of niter are useful in the
drinking water. If the fever is high, the antipyretics are indicated:
Sulphate of quinin in 1-dram doses; iodid of potash in 1-dram doses;
infusion of pine tops, of juniper leaves, of the aromatic herbs, or of
English breakfast tea are useful in the later stages. If complications
of the air passages or lungs are threatened, a large mustard poultice
should be applied to the belly and sides of the chest. Oxid of zinc
ointment should be used on confluent eruptions, and if the ulceration is
excessive it may have to be touched with caustic.
Great care must be taken to keep the animal protected from cold drafts
of air or other exposure. Blankets or sheets should be used on the body
and bandages on the legs. After convalescence is established, nutritious
feed of easy digestion and walking exercise are all that is needed,
except perhaps a little Glauber's salt to prevent constipation.
_Prophylactic treatment._--When horsepox breaks out among a large number
of horses, especially on a farm where there are a number of colts, it
may be assumed that the greater majority will contract the disease, and
it is more economical that they should have it and be through with it at
once. If the weather is moderate, all the animals which have not been
affected can be inoculated, which will produce the disease in a mild
form, with the eruption at a point of election, and render the danger of
complication a minimum one. For inoculation the discharge from the
pustules of a mild case should be selected and inoculated by
scarification on the belly or the under surface of the neck.
ANTHRAX.
_Synonyms:_ Carbuncle, splenic fever, splenic apoplexy, etc.;
charbon, sang de rate (French); Miltzbrand (German).
_Definition._--Anthrax is a severe and usually fatal contagious disease,
characterized by chills, great depression and stupor of the animal, and
a profound alteration of the blood. It is caused by the entrance into
the animal's body of a bacterium, known as the _Bacillus anthracis_, or
its spores.
Practically all animals are susceptible to anthrax. The herbivora are
especially susceptible, in the following order: The sheep, the ox, and
the horse. The guinea pig, the hog, the rabbit, mice, and other animals
die quickly from its effects. Man, the dog, and other omnivora and
carnivora may be attacked by it in a constitutional form as fatal as in
the herbivora, but fortunately in many cases develop from it only local
trouble, followed by recovery.
Anthrax has been a scourge of the animals of the civilized world since
the first written history we have of any of their diseases. In 1709-1712
extensive outbreaks of anthrax occurred in Germany, Hungary, and Poland.
In the first half of the nineteenth century it had become an extensively
spread disease in Russia, Holland, and England, and for the last century
has been gradually spreading in the Americas, more so in South America
than here. In 1864, in the five governments of Petersburg, Novgorod,
Olonetz, Twer, and Jaroslaw, in Russia, more than 10,000 horses and
nearly 1,000 persons perished from the disease.
_Causes._--The causes of anthrax were for a long time attributed
entirely to climatic influence, soil, and atmospheric temperature, and
they are still recognized as predisposing factors in the development of
the disease, for it is usually found, especially when outbreaks in a
great number of animals occur, in low, damp, marshy countries during the
warm seasons. It is more frequent in districts where marshy lands dry
out during the heat of summer and are then covered with light rains.
Decaying vegetable matter seems most favorable for nourishing and
preserving the virus.
The direct cause of anthrax is always infection of a previously sound
animal, either directly from a diseased animal or through various media
which contain excretions or the debris from the body of one previously
infected.
The specific virus of anthrax was first discovered by Davaine in 1851.
He recognized microscopic bodies in the form of little rods in the blood
of animals suffering from anthrax. It was not, however, till a quarter
of a century later that Pasteur defined the exact nature of the
bacillus, the mode of its propagation, and its exact relationship to
anthrax as the sole cause of the disease. In the animal body the bacilli
have a tendency to accumulate in the spleen, liver, and elsewhere, so
that these organs are much more virulent than the muscles or less
vascular tissues. When eliminated from the animal in the excretions, or
when exposed to outside influences by the death of the animal and the
disintegration of the tissues, the body of the rod is destroyed and the
spores only remain. These spores, which may be called the seeds of the
bacilli, retain their vitality for a long period; they resist ordinary
putrefaction; they are unchanged by moisture; and they are not affected
by moderate heat. If scattered with the debris of a dead animal on the
surface of the ground, they may remain around the roots of the grass in
a pasture or may be washed to the nearest low-lying ground or marsh. If
buried in the body of an animal dead from anthrax, they may be washed
deep into the ground, and in later years (in one proved case 17 years)
be brought to the surface and infect other animals. They are frequently
brought to the surface of the earth, having been swallowed by
earthworms, in the bodies of which they have been found.
This accounts for the outbreaks at the time of the first rains after a
dry season. During the latter the earthworm goes deep in the ground in
search of moisture; it finds the spore which has been washed there in
past years, swallows it, and afterwards brings it to the surface. The
virus is carried with the wool from infected sheep and remains in it
through the process of manufacture into cloth. The spores remain in the
hides of animals which have died of anthrax and retain their vitality
throughout months of soaking in the tanners' pits, the working of the
harness maker or the cobbler, and after the oiling of the completed
leather. The dried spores in the dust from any of these products may be
carried by the atmosphere.
Infection of an animal takes place through inoculation or contact of the
bacillus or its spores with an abraded surface or mucous membrane, on a
sound animal. In an infected district horses may eat with impunity the
rich pasturage of spring and early summer, but when grass gets low they
crop it close to the ground, pull up the roots around which the virus
may be lodged, and under these conditions the animals are more apt to
have abrasions of the lips or tongue by contact with dried stubble and
the dirt on the roots; this favors the introduction of the germs into
the system. The virus may be introduced with feed and enter the
blood-vessel system from the stomach and intestines. If in the dust,
dried hay, or on the parched pasture of late summer, the virus may be
inhaled and be absorbed from the lining of the lungs. If in harness
leather, it needs but an abrasion of the skin, as the harness rubs it,
to transfer the spore from the leather to the circulation of the animal.
The writer saw a case of anthrax occur in a groom from the use of a new
horse brush. The strap which passes over the back of the hand inoculated
an abrasion on the knuckle of the first finger, and in 12 hours a
"pustule" had formed and the arm had become infected.
_Symptoms._--The symptoms of anthrax usually develop with extreme
rapidity. The horse is dejected and falls into a state of profound
stupor, attended with great muscular weakness. The feeble, indolent
animal, if forced to move, drags its legs. There are severe chills,
agitation of the muscles, symptoms of vertigo, and at times colicky
pains. The mucous membranes turn a deep ocher or bluish-red color. The
body temperature is rapidly elevated to 104 deg. or 105 deg. F. The breathing is
increased to 30 or 40 respirations in the minute and the pulse is
greatly accelerated, but while the arteries are soft and almost
imperceptible, the heart beats can be felt and heard, violent and
tumultuous. In some cases, when inoculation is through the skin, large
subcutaneous swellings appear; these may involve a leg, a shoulder, one
side of the body, or the neck or head. The swelling is at first hot and
painful, but afterwards it becomes necrotic and sensation is lost. The
symptoms last but two, three, or four days at most, when the case
usually terminates fatally. An examination of the blood shows a dark
fluid which will not clot, and which remains black after exposure to the
air. After death the bodies putrefy rapidly and bloat up; the tissues
are filled with gases, and a bloody foam exudes from the mouth,
nostrils, and anus, and frequently the mucous membranes of the rectum
protrude from the latter. The hairs detach from the skin. Congestion of
all the organs and tissues is found, with interstitial hemorrhages. The
muscles are friable and are covered with ecchymotic spots. This is
especially marked in the heart.
The black, uncoagulated, and incoagulable blood shows an iridescent scum
on its surface, which is due to the fat of the animal dissolved by the
ammonia produced by the decomposed tissues. The serum oozes out of every
tissue and contains broken-down blood, which, when examined
microscopically, is found to have the red globules crenated and the
leucocytes granular. A high power of the microscope also reveals the
bacteria in the shape of little rodlike bodies of homogeneous texture
with their brilliant spores.
The lymphatic ganglia are increased four, five, six, or ten times their
natural size, enlarged by the engorgement of blood. The spleen shows
nodulated black spots containing a muddy blood, which is found teeming
with the virus. This organ is much enlarged and is quite friable. The
mucous membranes of the intestines are congested and reddish brown; the
surface of the intestines is in many places denuded of its lining
membrane, showing fissures and hemorrhagic spots. The liver has a cooked
appearance; the kidneys are congested and friable; the urine is red; the
pleura, lungs, and the meninges are congested, and the bronchi of the
lungs contain a bloody foam.
_Treatment._--Treatment of anthrax in animals by medicinal means has not
proved satisfactory. In cases of local anthrax an incision of the
swelling followed by the application of disinfectants sometimes causes
good results. In such cases, however, the danger of disseminating the
infection from the wounds tends to make this procedure inadvisable
unless great care is taken.
Good results are obtained from the use of serum in the treatment of the
disease. For this purpose 30 to 100 cubic centimeters should be
administered subcutaneously or intravenously. If no improvement is
noticed within 24 hours the injection should be repeated. In a number of
instances afforded to test the curative value of the serum in cases of
anthrax in man and animals splendid results were obtained.
The prophylactic treatment formerly consisted in the avoidance of
certain fields and marshes which were recognized as contaminated during
the months of August and September and had been occupied the years in
which the outbreaks usually occurred. It underwent, however, a
revolution after the discovery by Pasteur of the possibility of a
prophylactic inoculation or vaccination which granted immunity from
future attacks of the disease similar to that granted by the recovery of
an animal from an ordinary attack of the disease.
This treatment consists in the use of a vaccine which is made by the
artificial cultivation of the virus of anthrax in broth and in the
treatment of it by means of continued exposure to a high temperature for
a certain time, which weakens the virus to such extent that it is
capable of producing only a very mild and not dangerous attack of
anthrax in the animal in which it is inoculated, and thus protects it
from inoculation of a stronger virus. The production of this virus,
which is carried on in some countries at the expense of the governments
and is furnished at a small cost to the farmers in regions where the
disease prevails, in this country is made in private laboratories only.
At the present time very good results are being obtained with
vaccination consisting of an injection of highly potent anthrax serum on
one side of the animal and a vaccine on the other side. This method of
treatment requires only a single handling of the animals and further
possesses advantages over the Pasteur treatment in that it immediately
makes animals immune. In the numerous applications of this form of
treatment very good results have been obtained and the immunity produced
thereby visually lasts at least one year. The vaccinated animals should
be kept for a period of ten days to two weeks from exposure, since
during that period they are at times even more susceptible to the
disease, and therefore care should be taken not to reduce their
vitality.