Special Report on Diseases of Cattle Part 55

The disease of the stomach, intestines, and mesenteric glands is very probably the result of feed infection. Tubercle bacilli may have been scattered upon the feed by diseased animals, but the most common source of such infection is the milk of tuberculous cows. Calves may become infected in this way. The disease may remain latent until the animal becomes older.

The not-infrequent occurrence of tuberculosis of the uterus and ovaries makes it probable that the disease may be transmitted by a diseased bull or carried by a healthy one from a diseased cow to a number of healthy cows.

The source of infection is always some previous case of the disease, for the disease can never rise spontaneously; hence, in those stables in which there is frequent change of cattle the introduction of tuberculosis by cattle coming from other infected stables is the most frequent source of infection. Since the bacilli when dried can be carried by the air, it is not necessary that healthy animals come in direct contact with cases of disease to become infected. In general, the greatest number of cases occur in the immediate environment of cities, where there are not only abundant opportunities for infection, owing to the frequent introduction of new animals into herds, but where the sanitary conditions may be regarded as the poorest.

The bacillus of tuberculosis was discovered by Robert Koch in 1882. It is a slender, rodlike body (see Pl. XXVIII, fig. 6) from one-third to two-thirds the diameter of a red blood corpuscle in length. As already explained, when the bacillus has become lodged in any organ or tissue it begins to multiply, and thereby causes an irritation in the tissue around it, which leads to the formation of the so-called tubercle. The tubercle, when it has reached its full growth, is a little nodule about the size of a millet seed. It is composed of several kinds of tissue cells. Soon a change takes place within the tubercle. Disintegration begins, and a soft, cheesy substance is formed in the center, which may contain particles of lime salts. When these tubercles continue to form in large numbers they run together, forming ma.s.ses of various sizes. The disintegration which attacks them leads to the formation of large cheesy ma.s.ses of a yellowish color, containing more or less of lime salts in the form of gritty particles.

These large tuberculous ma.s.ses are surrounded by or embedded in layers of fibrous tissue which in some cases becomes very dense and thick.

The disease is thus a development of these tubercles in one or more organs of the body. The distribution and number of the tubercles determine the course of the disease.

In a large number of cases the changes are limited to the lungs and the serous membranes[4] of the thorax and abdomen. Pathologists have been in the habit of calling the lung disease tuberculosis and the disease of the serous membranes "pearly disease." Statistics have shown that in about one-half of the cases both lungs and serous membranes are diseased, in one-third only the lungs, and in one-fifth only the serous membranes. At the same time the lymphatic glands near the diseased organs are usually involved. Other organs, such as the liver, not infrequently contain tubercles. Though the disease may remain restricted to a single organ, it now and then is found generalized, affecting all organs of the body.

In the lungs (Pl. x.x.xIV) the changes observed vary according to the age and intensity of the disease process. They usually begin with the appearance of very minute tubercles. These may appear in large numbers on the surface of the lungs or within the lung tissue. Later the contents become cheesy and partly calcified. When these tubercles are sufficiently numerous to become confluent, large ma.s.ses may be formed, which undergo the same retrogressive changes of caseation and calcification. In addition to the formation of tubercles in the lung tissue, certain other changes take place. There is usually bronchitis with abundant catarrhal secretion; this plugs up the smaller air tubes, and the lung tissue supplied with air by the tubes collapses. Subsequently it becomes filled with yellowish, cheesy matter, which greatly distends the small air tubes and air vesicles (bronchopneumonia). The connective tissue between the lung lobules, around the tubercles, and around the air tubes becomes thickened and indurated. In the larynx and the bronchi tubercles may vegetate upon the mucous membrane, and ulcers may result from their breaking down. The inflammatory irritation which the growth of the tubercles on the surface of the lungs arouses gives rise to adhesion of the lungs to the ribs and diaphragm. This adhesion is sometimes so firm and extensive that the lungs appear grown to the chest wall.

When, therefore, the lungs in advanced stages of the disease are cut open we observe large yellowish ma.s.ses, from one-quarter to three-quarters of an inch in diameter, of a cheesy texture, in which calcified, gritty particles are embedded and which are surrounded by very firm connective tissue. The neighboring lung tissue, when collapsed and involved in bronchopneumonia, has the color and consistency of pale-red flesh. The air tubes, large and small, stand out prominently on the cut surface. They are distended with a pasty, yellowish, cheesy ma.s.s, surrounded and enveloped in thick mucus, and their walls greatly thickened. The larger bronchi may be sacculated, owing to the distention produced by the cheesy contents.

The disease usually attacks the bronchial glands, which are situated on the trachea and bronchial tubes at the bifurcation. The changes in the glands are the same as those going on in the lung tissue, and they frequently reach an enormous size.

The tubercle formation on the serous membranes covering the lungs and chest wall (Pl. x.x.xVII, fig. 2), which may go on at the same time with the lung disease or independent of it, has been called "pearly disease," on account of the peculiar appearance of the tubercles. These begin as very minute, grayish nodules, which give the originally smooth, l.u.s.trous membrane a roughened appearance. These minute tubercles enlarge, become confluent, and project above the surface of the membrane as wartlike ma.s.ses, attaining the size of peas. In this stage their attachment to the membrane is by means of delicate fibers. The attachment is loose, so that the tubercle hangs by a short pedicle or neck and may be moved slightly to and fro. Large ma.s.ses are frequently formed by a coalescence of many tubercles and the secondary formation of the same. These may be found on the lungs, the ribs, and the diaphragm. These tubercles likewise undergo degenerative changes. The center partly softens and partly calcifies into a grayish mortarlike ma.s.s, and is gritty. a.s.sociated with the formation of tubercles on the pleura, those glands situated back of the center of the lungs between the two main lobes (posterior mediastinal) become greatly enlarged and the center cheesy. (Pl. x.x.xVI, fig. 1.) They may compress the esophagus and interfere with swallowing. The size attained by these tumors and new growths is well ill.u.s.trated by the fact that, taken together, they not infrequently weigh from 60 to 80 pounds. The bronchial glands, which in the healthy state are not so large as horse-chestnuts, have been found to attain a weight of more than 10 pounds.

In the abdominal cavity tubercles may be found, both in the organs and on the serous membranes covering them. They are situated usually on the omentum, or caul (see Pl. x.x.xVI, fig. 2), the diaphragm, and the walls of the abdomen. In the liver large and small tubercular ma.s.ses are occasionally encountered. (See Pl. x.x.xV.) The mesenteric glands are occasionally enlarged and tuberculous; likewise the glands near the liver.

Tubercles may also develop in the spleen, the kidneys, the uterus and ovaries, and the t.e.s.t.i.c.l.es.

Tubercular affection of the intestines seems to be quite rare, although ulcers of the large intestines have been observed. Nodules may also form under the serous covering of the intestines.

The brain and spinal cord are occasionally found tuberculous. Of 40 cases, Semmer found tuberculosis of the brain in 4. It is not improbable that, owing to the infrequency of exposing the brain and spinal cord, tuberculosis may have escaped the attention of pathologists, and it may be that it is not so uncommon as is generally supposed. The tubercles occur on the membranes of the brain as well as in the substance of the brain itself.

They project into the ventricles as ma.s.ses, varying in size from a pinhead to a hen's egg. They finally lead to various inflammatory changes. Johne has observed numerous small tubercles on the membranes of the spinal cord.

Very rarely tuberculous lesions have been observed in the bones and muscles of the body. Not so rare, however, is the affection of the lymphatic glands embedded in the muscular tissue, and those which can be felt beneath the skin. These are situated at the joints, under the jaw, and along the neck.

Of late tubercular disease of the udder in cows (Pl. x.x.xVIII) has received considerable attention from sanitarians, owing to the infection of the milk with the virus of tuberculosis. According to those who have given this subject special attention, the udder becomes swollen uniformly and quite firm. This swelling, which is painless, frequently attacks but one quarter, more rarely two, these being usually the hind quarters. The larger milk ducts contain yellowish, cheesy particles, in which are many tubercle bacilli. Later larger nodules can be felt within the udder, which undergo the various changes to which tubercles are subject. The udder may grow very hard to the touch and become very large, weighing in some cases up to 40 pounds. The milk, at first normal, becomes thin and watery after a month or so, and is mixed with flakes and tubercle bacilli.

As regards the frequency of the tuberculous processes in the different organs, the following carefully compiled statistics of the disease in Bavaria and Baden may serve as a guide:

Bavaria: Per cent.

Tuberculosis of lungs and serous membranes 41 Tuberculosis of lungs alone 33 Tuberculosis of serous membranes alone (pearly disease) 17 Tuberculosis of other organs 8

Baden: Tuberculosis of lungs alone 21 Tuberculosis of serous membranes alone 28 Both combined 39 Generalized tuberculosis 9 Tuberculosis of the s.e.xual organs alone 3

_Symptoms._--The beginning of the disease usually pa.s.ses unnoticed, inasmuch as it is very slow and insidious and rarely accompanied with fever. When the lungs are involved a dull, short cough is noticed, which may later on become prolonged, convulsive, and very troublesome to the animal. The cough is more frequent in the morning after movement and drinking. The breathing varies. Only when much of the lung tissue is diseased is it labored and accompanied with active movements of the chest and nostrils. Discharge from the nose is rare or absent. At times, however, when the tubercles have broken down and cavities containing cheesy ma.s.ses have formed in the lung tissue, or when the air tubes have become filled with cheesy and mucous ma.s.ses, coughing will dislodge them and cause their discharge. In advanced stages the breath may have a disagreeable odor.

Pressure on the chest wall may give rise to pain.

The general effect on the body is at first slight. In fact, animals may remain in good flesh for a considerable time. Invariably as the disease progresses loss of flesh and appet.i.te and paleness of the mucous membranes become manifest. These symptoms are accompanied with a gradual diminution of the milk secretion. The debilitated condition of the animal is also manifested by a staring coat and a tough, dry, harsh skin (hidebound).

Digestive disturbances are indicated by tympanites, or distention of the rumen by gas, colic, and diarrhea, alternating with constipation. The animal generally dies from exhaustion after a period of sickness which may last months or even years.

[Ill.u.s.tration: PLATE x.x.xIV. TUBERCULOSIS OF THE LUNGS OF CATTLE.]

[Ill.u.s.tration: PLATE x.x.xV. TUBERCULOSIS OF THE LIVER.]

[Ill.u.s.tration: PLATE x.x.xVI. TUBERCULOSIS OF LYMPH GLAND AND OF OMENTUM (CAUL).]

[Ill.u.s.tration: PLATE x.x.xVII. FIG. 1.--TUBERCULOSIS OF SIRLOIN AND PORTERHOUSE CUTS OF BEEF.

FIG. 2.--TUBERCULOSIS OF PLEURA OF A COW, SO-CALLED "PEARLY DISEASE."]

[Ill.u.s.tration: PLATE x.x.xVIII. TUBERCULOSIS OF COW'S UDDER.]

TUBERCULOSIS.

DESCRIPTION OF PLATES.

PLATE x.x.xIV. Tuberculosis of the lungs of cattle. The upper figure represents a large cheesy ma.s.s, surrounded by a capsule of connective tissue, the whole embedded in healthy lung tissue. The lower figure ill.u.s.trates in section a ma.s.s of tubercles which have undergone cheesy degeneration, and some of which are surrounded by dense connective tissue.

PLATE x.x.xV. Tuberculosis of the liver. A large portion of the lobe represented in the plate has undergone tuberculous changes. Numerous nodules are shown in various stages of the disease, the majority of which, however, contain the yellowish, partly cheesy, partly gritty areas characteristic of advanced tuberculous degeneration. This large ma.s.s involves the surface of the liver, and also extends into the liver substance.

PLATE x.x.xVI. Tuberculosis of lymph gland and of omentum (caul).

Fig. 1. A lymph gland from the region of the thorax behind or above the esophagus, or gullet (posterior, or dorsal, mediastinum). The gland is shown cut through and laid open. It is very much enlarged, and the yellowish cheesy ma.s.ses which represent tissue undergoing tuberculous changes are well shown on the cut surface.

Fig. 2. Omentum, or caul, resting upon the paunch. The reddish nodules with which the membrane is beset are tubercles, the product of the disease.

PLATE x.x.xVII. Fig. 1. Tuberculosis of the sirloin and porterhouse cuts of beef. The grapelike tuberculous growths are mainly restricted to the lining membrane of the abdomen.

Fig. 2. Tuberculosis of the pleura of a cow, so-called "pearly disease."

Notice the grapelike cl.u.s.ters of tubercular nodules scattered over the lining membrane of the chest (pleura).

PLATE x.x.xVIII. Tuberculosis of cow's udder. The udder was uniformly swollen and quite firm. Small cheesy foci and yellowish lines of tuberculous material follow the course of the milk ducts. The mucous membrane of the milk cistern (_a_) is ulcerated and covered with yellowish cheesy particles. The supramammary lymphatic gland (_b_) is greatly enlarged and contains many miliary tubercular foci.

Tuberculosis in the abdominal organs is often signalized by abortion and by abnormal s.e.xual manifestations. When the brain is involved, the disease may cause convulsions, unconsciousness, paralysis, as well as peculiar movements in a circle, oblique position of the head, etc. Lydtin quotes the following description of the disease as taken from a Swiss sanitary order:

A dry, short, interrupted, hoa.r.s.e cough, which the sick animals manifest, especially in the morning at feeding time, still more after somewhat violent exertion. At first these animals may be full blooded and lay on a considerable amount of fat when well fed. As the disease progresses they grow thin and show more and more those appearances which indicate diseased nutrition, such as a staring, l.u.s.terless, disheveled coat; dirty, tense skin, which appears very pale in those regions free from hair. The temperature of the skin is below normal. The loss of fat causes sinking of the eyes in their sockets. They appear swimming in water, and their expression is weak. The cough is more frequent, but never or very rarely accompanied with discharge. The body continues to emaciate, even with plenty of food and a good appet.i.te, so that the quant.i.ty of milk is small. At times in the early stages of the disease, still more in the later stages, the diseased animals manifest considerable tenderness when pressure is applied to the front or the sides of the chest by coughing, moaning, etc. Often symptoms are wanting in spite of the existence of the disease.

Lydtin also quotes at length a description of the abnormal s.e.xual desire occasionally observed among cows when affected with this disease.

_Diagnosis._--A disease so varied in its attack upon the different organs of the body and in the extent of the disease process must necessarily lead to mistakes when diagnosis is attempted by ordinary means of examination.

It has been confounded with the later stages of pleuropneumonia, with parasitic diseases of the brain, the lungs, the intestines, and with actinomycosis. A careful examination of the lungs by auscultation and percussion enables the expert to locate large tuberculous ma.s.ses, owing to dullness, loss of respiratory murmur, and abnormal sounds, such as blowing, whistling, and creaking. The majority of cases of tuberculosis in cattle, however, including many in which the lungs are quite seriously involved, can not be detected in this manner.

THE TUBERCULIN TEST.

The tuberculin test, which is marvelously accurate in its indications, has been almost universally adopted for the detection of tuberculosis.

Tuberculin is a drug prepared by sterilizing, filtering, and concentrating the liquids in which the tubercle bacillus has been allowed to vegetate. It contains the cooked products of the growth of these bacilli, but no living bacilli; consequently, when this substance is injected under the skin of an animal it is absolutely unable to produce the disease, cause abortion, or otherwise injure the animal. In case the injected animal is normal there is no more effect upon the system than would be expected from the injection of sterile water; however, if the animal is tuberculous, a decided rise of temperature will follow the use of tuberculin by the subcutaneous method.

This substance, discovered by Koch, has the effect, when injected into the tissues of a tuberculous animal, of causing a decided rise of temperature or other manifestations while it has no such effect upon animals free from the disease. The value of tuberculin for this purpose was tested during the years 1890 and 1891 by Guttman, Roeckl and Schutz, Bang and Salomonsen, Lydtin, Johne and Siedamgrotzky, Nocard, and many others. It was at once recognized as a most remarkable and accurate method of detecting tuberculosis even in the early stages and when the disease had yet made but little progress. It is now quite generally employed.

The tuberculin test came into existence through the most careful and thorough scientific experimentation.

As a result of its use an accurate diagnosis may be established in more than 90 per cent of the cases tested. The relatively few failures in diagnoses are included among two cla.s.ses of cattle. The first cla.s.s contains those that are tuberculous, but which do not react either because of the slight effect of an ordinary-sized dose of tuberculin on an advanced case of the disease with so much natural tuberculin already in the system, or on account of a recent previous test with tuberculin which produces a tolerance to this material, lasting for about six weeks. The second cla.s.s includes those that are not tuberculous, but which show indications of a reaction as a result of (_a_) advanced pregnancy, (_b_) the excitement of [oe]strum, (_c_) concurrent diseases, as inflammation of the lungs, intestines, uterus, udder, or other parts, abortion, retention of afterbirth, indigestion, etc., (_d_) inclosure in a hot, stuffy stable, especially in summer, or exposure to cold drafts or rains, (_e_) any change in the method of feeding, watering, or stabling of the animal during the test. Notwithstanding all these possibilities of error, the results of thousands of tests show that in less than 3 per cent of the cases tested do these failures actually occur. In the first cla.s.s the chances of error are decidedly reduced by the skilled veterinarian by making careful physical examination and diagnosing clinically these advanced cases, and by the injection of double or triple doses into all recently tested cattle, with the taking of the after-temperature, beginning two hours following the injection and continuing hourly for 20 hours.