Chapter 47

_Symptoms._--Three forms of the disease are recognized, based upon the distribution of the lesions--the superficial, or cutaneous, the pectoral, or thoracic, and the intestinal form. The last is a usual accompaniment of the other two and may be mild or severe. Naturally the symptoms vary according to the violence of the attack and to the particular form of disease with which the animal is affected. In the superficial, or cutaneous, form the presence of a swollen tongue, throat, and dewlap, or even of the lower portion of the legs, gives us a clew to the trouble. An entire loss of appetite occurs, and in milk cows there is a diminution of the milk secretion. The temperature may be only slightly elevated, but it is usually very high. Salivation is set up by the inflammation of the mouth and pharynx. Unsuccessful efforts at eating and swallowing are made. There may be difficulty in breathing, depending on the amount of involvement of the larynx, trachea, bronchi, or lungs. There may be a blood-stained discharge from the nostrils, and the mucous membrane thereof will often show punctiform hemorrhages. The pulmonary form shows the same symptoms as croupous pneumonia, with a frequent suffocative cough and oppressed breathing, or dyspnea. When the intestines are involved the patient strains to defecate, and passes shreds of intestinal mucus along with blood-stained feces. The urine also may be tinged with blood. Finally a severe diarrhea takes place, the animal becomes correspondingly weak, and death takes place in 24 to 36 hours. Cases may die in as short a period as six to eight hours, while in the pectoral form of the disease the animal may linger six or eight days. Cases have been reported which became chronic and in which death did not take place for a month or more. In some of the cases running an acute course, symptoms of toxemia are present; there is a lack of sensation of the skin, staggering gait, trembling, eyes fixed, neck at times bent to one side, and the eyes showing a wild expression. At times the animals appear as if in pain and look around at the flanks. In the pectoral form they may stand with the forelegs wide apart in evident effort to breathe more freely. Sometimes there is a champing of the jaws and a very free flow of glairy saliva dropping from the mouth.

The prognosis is decidedly unfavorable and 80 to 90 per cent of the cases result fatally.

_Lesions._--The characteristic lesions of hemorrhagic septicemia consist of hemorrhagic areas in the subcutaneous, subserous, and muscular tissues, the lymph glands, and the viscera; in fact, they are distributed more or less widely throughout the body and vary in size from a mere speck to the diameter of a half dollar or even larger. The superficial form presents itself first as a doughy tumefaction of the skin about the region of the throat, neck, dewlap, or legs, which pits on pressure. This tumefaction consists essentially of a cerogelatinous exudate into the subcutaneous and intermuscular tissues.

Bloody extravasations may take place in subcutaneous tissues in various places, but they are usually seen about the lower portion of the neck. The mucous membranes and submucous tissues of the mouth, tongue, pharynx, and larynx become involved in the process and are greatly thickened, inflamed, and infiltrated with serum. The mucous membrane becomes reddish purple, and that of the nostrils may in addition show hemorrhagic spots on its surface. The lymphatic glands in this region are also swollen and infiltrated with bloody serum. The salivary glands are pale and dry. The pectoral type, though at times existing alone, may coexist with the cutaneous form. The inflammatory edema of the mouth extends to the mucous membrane of the trachea and bronchi, producing an extensive thickening and a yellowish infiltration. The lung shows interstitial thickening from the outpouring of serum into its meshes. It may become pneumonic.

The diaphragm, heart sac, and heart walls show numerous hemorrhagic points and larger bloody extravasations. Sometimes there is a serous pleurisy, with more or less fibrinous exudate. In the intestinal form the submucous and subperitoneal tissues show alterations from a few hemorrhagic spots to large bloody suffusions, or even gelatinous infiltrations. This latter is seen about the region of the pancreas and in the folds of the mesentery. There is a severe hemorrhagic inflammation of the intestines and a staining of the intestinal contents with blood. The muscular system throughout shows hemorrhagic areas. The abdominal viscera, liver, spleen, and kidneys often present hemorrhagic lesions.

_Differential diagnosis._--Anthrax, which presents superficial swellings, like hemorrhagic septicemia, may be distinguished from that affection on post-mortem examination by the enlargement and engorgement of the spleen, the contents of which are soft and tarry. The blood of anthrax animals is very dark, and does not become light red on exposure to air, nor does it coagulate, while in hemorrhagic septicemia the blood is normal in appearance and coagulates. The detection of the anthrax bacillus in the blood would be final.

In blackleg the animals affected are usually under 2 years of age. The swellings are quite evident, and usually occur on the legs, above the knees or hocks, and are distended with gas, which crackles, or crepitates, when pressed upon. If one of these tumors is opened, a bloody serum will exude, and the gas gives off the odor of rancid butter. The internal hemorrhages are not general, although they may occur. A microscopic examination of the juices from the tumefaction will show the blackleg bacillus.

In cerebrospinal meningitis the causative agent is unknown, but probably exists in the feed. It may occur in any locality and at any season of the year. There are no local swellings, and cattle are not frequently affected.

Cornstalk disease may be differentiated from this affection from the fact that it always occurs after the cattle are turned into a cornstalk field, by its sudden onset, the absence of any characteristic symptoms or post-mortem lesions, and the failure to find the causative agent in the blood.

In making a post-mortem examination of animals affected with hemorrhagic septicemia, it would be well to examine the articular surfaces of the long bones, as it has been reported that they are frequently ulcerated. This should apply especially to those cases that have shown lameness.

_Treatment._--Treatment is absolutely useless, so far as we know at present, and for all practical purposes prophylaxis alone should be relied upon. The same sanitary precautions, such as isolation, disinfection, and burial or burning of all dead carcasses, should be observed as for anthrax and other highly infectious diseases. All the premises, barns, stalls, litter, and stable utensils should be thoroughly disinfected. Separate the apparently well animals from the sick by placing them in a separate lot.

Experiments by the Bureau of Animal Industry toward protective inoculation of the exposed cattle on infected premises have been made and the results have been so satisfactory that several commercial houses handling biological products are manufacturing a vaccine for hemorrhagic septicemia in accordance with the Government's experiments on this subject. The method of preparing the vaccine is similar to that recommended by LigniËres. It consists in growing the cultures of the organism of the disease at 42 to 43∞ C. and preparing from them growing at this temperature two different strengths of vaccine. The weaker vaccine, which is used for the first injection, is grown for five days at this temperature, whereas the stronger vaccine, for the second injection, is grown for only two days. These vaccines are used with an interval of 10 days between the injections, the dose being 1 cubic centimeter at each injection. The effect of this vaccine in abating outbreaks already in progress has been highly satisfactory and it is plain that the general introduction of preventive vaccination for hemorrhagic septicemia must be of material benefit to the cattle raisers in the infected districts.

VESICULAR ERUPTION OF THE GENITAL ORGANS.

This contagious disease is called coital exanthema or vesicular exanthema, and is more or less prevalent on the Continent. It has also been observed in the breeding districts of the United States. It is the subject of legislation in Germany, and governmental statistics are published annually concerning its distribution in the Empire. According to the reports from Hungary 492 head of cattle were attacked during 1898, 587 in 1899, and 207 in 1900.

A similar or perhaps identical disease of horses has the same distribution and is transmissible from horses to cattle and vice versa.

The disease may be defined as a highly contagious eruption situated upon the external genital organs of both sexes and accompanied with little or no general disturbance of health. The contagion, the nature of which remains still unknown, is transmitted mainly during copulation. The bull may have the disease and convey it to all the cows with which he comes in contact, or he may become infected by one cow, and, although not showing the disease, he may, during copulation, transmit it for several days after to all other cows. Simple contact between one cow and another may convey the disease, or the sponges used in cleaning the diseased may carry the virus to the healthy. It has also been conveyed to healthy cows by these animals lying with their hind quarters against infected wooden troughs.

_Symptoms._--The period between the infection and the appearance of symptoms is somewhat variable. It is usually given as three to six days. It may be briefer or much longer. In cows the mucous membrane of the vagina and the vulva become swollen, inflamed, very tender, and covered with dark-red spots. The secretion is very abundant and consists at first largely of serum and mucus resembling the white of an egg. Small vesicles then appear, which rapidly burst and are converted into excoriations or deeper ulcerations. The secretion becomes more purulent and is apt to dry in crusts about the root of the tail. The eruption is accompanied with much itching and difficulty in urinating. The walk may be stiff and awkward. In bulls the eruption is situated on the prepuce and the end of the penis, and consists of pimples, vesicles, and ulcers, as in cows. It is accompanied with a little purulent discharge from the prepuce, itching, and difficulty in urinating. In severe cases the inflammation and swelling may extend backward to the scrotum and forward upon the abdomen.

The disease lasts from one to four weeks and always terminates in recovery. The acute stage lasts only four or five days, while the complete healing of the inflammation is slow. The eruption is usually accompanied with very little general disturbance. If the pain and irritation are severe, there may be some light loss of appetite and diminished milk secretion in cows. The disease rarely causes abortion. Chronic catarrh of the vagina and permanent sterility frequently follow as sequelÊ.

_Treatment_ need not be resorted to excepting in severe cases. The secretion and exudation should be washed off and a mild antiseptic applied, such as a 1 per cent solution of carbolic acid (1 ounce to 3 quarts of water) or 2 per cent solution of cresol compound in water. Care must be taken not to carry the disease from the sick to the well by sponges, etc., which have come in contact with the affected organs. These should be destroyed. To prevent the spread of the disease the infected animals should be kept isolated until they have recovered.

RABIES OF CATTLE.

Rabies is a disease preeminently affecting the canine race, although all warm-blooded animals, including man, are susceptible to the malady, which is always communicated through bites from a preceding case. It has required many years of patient, scientific research to lead the ablest investigators to a clear comprehension of the cause, nature, and characteristics of this affection. It was known and described several centuries prior to the beginning of the Christian era, and from the earliest dawn of history it has been feared and dreaded. Its terrible manifestations have always been surrounded with an atmosphere of awe and mystery, and it is not surprising that myths, fallacies, and misconceptions in regard to it have been common and widely accepted. As the investigations by which we have come to a tolerably clear understanding of the facts concerning rabies have been comparatively recent, and for the most part, have appeared in scientific periodicals, fallacies in regard to the disease continue to have a strong hold upon the public mind. For instance, it is still a widely prevalent belief that if persons or animals are bitten by a dog they are liable to become rabid if the dog should contract the disease at any future time. There is no foundation for this impression, and it would be a great comfort to many people who are now and then bitten by animals if the fallacy of this idea were known. All experience, both scientific and practical, goes to show that rabies is transmitted only by animals that are actually diseased at the time the bite is inflicted. Rabies is an infectious disease involving the nervous system and characterized by extreme excitability and other nervous disorders and always terminating in death. The contagion of this disease has never been isolated, but the fact that it is caused by a specific organism principally found in the nervous system is indisputable. For instance, if an emulsion of the brain of a rabid animal is filtered through a germ-proof filter, the filtrate will be harmless. This fact indicates that the infectious principle is not in solution, but is an organism withheld from the filtrate by the filter. This contagion can be propagated only in the body of an animal. It is transmitted naturally from one animal to another solely by bites, and the old idea of spontaneous appearance of the disease is absolutely fallacious. It may be produced artificially by inoculating susceptible animals with an emulsion of the brain or spinal cord, as well as the saliva, milk, and other secretions of the affected animal. The blood, on the contrary, seems to be free from the infectious principle. The saliva contains the virus, which, under natural conditions, is introduced into or under the skin on the tooth of the rabid animal. The disease is widespread, being found in many countries of Europe, Asia, and Africa, and in certain sections of the United States.

Owing to the rigid quarantine regulations enforced against dogs imported into Australia, that country remains absolutely free from the disease. Following the canine race, cattle seem to be the most frequently affected, probably because rabid dogs, next to their morbid desire to attack other members of their own race, have a better opportunity to bite grazing cattle than any other species of animal. The relative frequency of rabies in these two species of animals is indicated by the carefully compiled statistics of the German Empire, which shows that 904 dogs and 223 cows died of rabies in 1898, while in 1899 there were 911 cases in dogs and 171 in cattle. The latter receive bites most frequently on the hind legs and in the hips and about the lower jaw. These places are most accessible to dogs, owing to the habit of cattle to drive their tormentors away by lowering their heads and using their horns. Every animal bitten does not necessarily develop the disease, but the per cent of fatalities has been variously estimated, and averages from 25 to 30. This, however, depends on the location and size of the wound as well as the amount of hemorrhage produced, and various other conditions. In general, the nearer the bite is located to the central nervous system and the deeper the wound inflicted, the greater the danger of a fatal result. In cases in which the hemorrhage resulting from the bite is profuse, there is a possibility that the virus will be washed out of the wound and thus obviate the danger of subsequent appearance of the disease.

The virus after being deposited in the wound remains latent for an extremely variable period of time, which also depends on the size and depth of the wound as well as its location and the amount of the virulent saliva introduced. Experiments have proved that the virus follows the course of the nerves to the spinal cord and along the latter to the brain before the symptoms appear. Gerlach, having collected the statistics from 133 cases, has found this time, known as the period of incubation, to vary from 14 to 285 days. The great majority of cases, however, contract the disease in one to three months after the bite has been inflicted.

_Symptoms._--As in dogs, both furious and dumb rabies are met with, the former being more common in cattle. A sharp line of distinction, however, can not be drawn between these two forms of the disease, as the furious form usually merges into the dumb, from the paralysis which appears prior to death. The typical cases of dumb rabies are those in which the paralysis appears at the beginning of the attack and remains until death. The disease first manifests itself by a loss of appetite and rumination, stopping of the secretion of milk, great restlessness, anxiety, manifestation of fear, and change in the disposition of the animal. This preliminary stage is followed in a day or two by the stage of excitation, or madness, which is indicated by increasing restlessness, loud roaring at times with a peculiar change in the sound of the voice, violent butting with the horns and pawing the ground with the feet, with an insane tendency to attack other animals, although the desire to bite is not so marked in cattle as in the canine race. A constant symptom is the increased secretion of saliva with a consequent frothing at the mouth, or the secretion may hang from the lips in long strings. Constipation is marked, and there is manifested a continual, although unsuccessful, desire to defecate. Spasms of the muscles in different parts of the body are also seen at intervals. About the fourth day the animal usually becomes quieter and the walk is stiff, unsteady, and swaying, showing that the final paralysis is coming on. This is called the paralytic stage. The loss of flesh is extremely rapid, and even during the short course of the disease the animal becomes exceedingly emaciated. The temperature is never elevated, it usually remaining about normal or even subnormal. Finally, there is complete paralysis of the hind quarters, the animal being unable to rise, and but for irregular convulsive movements lies in a comatose condition and dies usually from the fourth to the sixth day after the appearance of the first symptom.

_Anatomy._--If animals which have succumbed to rabies are examined post mortem, very slight evidence of disease will be found in any of the organs, and, indeed, the absence of any specific lesions may be considered as characteristic. The blood is dark and imperfectly coagulated. The throat is frequently reddened, and there may be small spots of extravasated blood in the intestines. The stomachs are usually empty. In the spleen there may be hemorrhagic enlargements (infarcts). The cadavers rapidly undergo decomposition.

_Differential diagnosis._--It is not an easy matter to decide definitely that a given animal has rabies, since the symptoms given above belong in part to a variety of other diseases, among which may be mentioned the excitement seen in young animals following close confinement, certain vegetable and mineral poisons, acute enteritis, and alterations of the central nervous system in cattle, the most common of which is tuberculosis of the brain and its covering membranes. The post-mortem lesions, however, should assist in making a correct diagnosis. Tetanus may readily be differentiated from rabies by the persistence of muscular cramps, especially of the face and abdomen, which cause these muscles to become set and as hard as wood. In tetanus there is also an absence of a depraved appetite or of a willful propensity to hurt other animals or to damage the surroundings. The cow remains quiet and the general muscular contraction gives her a rigid appearance. There is an absence of paralysis which marks the advanced stage of rabies. The form of dumb rabies in dogs is characterized by the paralysis and pendency of the lower jaw, while in tetanus the jaws are locked. This locking of the jaws in cattle renders the animal incapable of bellowing, as in rabies. Finally, tetanus may be distinguished from rabies by the fact that the central nervous system does not contain the infectious principle, while in rabies the inoculation of test rabbits with the brain or cord of a rabid animal will produce the disease with characteristic symptoms after an interval of 15 to 20 days. This period of incubation is much longer than in tetanus, since the inoculation of rabbits with tetanus cultures invariably results in death after a short period and usually within three days. The positive evidence that a rabid dog has been near cattle would greatly assist in making a decision in doubtful cases.

The disease in dogs is pretty well recognized by most people, but in case a suspected dog is killed it is desirable to open the animal and examine the contents of the stomach. While feed is absent, a variety of odd things may be present which the abnormally changed appetite of the rabid dog has induced it to swallow. Among such things may be straws, sticks, glass, rags, earth, pieces of leather, and whatever the animal may have encountered small enough to be swallowed. This miscellaneous collection in the stomach of dogs, together with absence of feed, is regarded by authorities as a very valuable sign, and in case of doubt may be made use of by laymen. In important cases, however, the head of the dog, cow, or other suspected animal should be removed and sent to the nearest biological laboratory, where a positive diagnosis can be made within 36 hours by the histological examination of the plexiform nerve ganglia, and within two or three weeks by the intracerebral inoculation of rabbits with an emulsion of the brain of the suspected animal.

_Treatment._--This is useless after the first appearance of symptoms. When, however, a wound inflicted by a rabid animal can be discovered, it should be immediately cauterized or even completely extirpated, care being taken to cut entirely around the wound in the healthy tissues. For cauterizing the wound, fuming nitric acid, the hot iron, and 10 per cent solution of zinc chlorid are the most efficacious. To afford an absolute protection, this should be done within a few moments after the bite has been inflicted, although even as late as a few hours it has been known to thwart the development of the disease.

Pasteur originated and perfected a system of preventive inoculation against this disease which has greatly reduced the mortality in human subjects. Its application to animals, however, is difficult and requires considerable time and expense. A method of vaccination applicable to animals, consisting of a single injection of a suspension of "fixed" rabies virus, is now being quite extensively employed by veterinarians. Sanitary regulations which seek to control effectively the disease by exterminating it among dogs are most likely to prove successful. The measures which are adopted to this end can not be discussed in this place, but it is a striking fact that where the muzzling of all dogs has been rigidly enforced, as in England and in certain German districts, the disease has been practically stamped out.

TUBERCULOSIS.

[Pls. XXXIV-XXXVIII.]