Microscope and staining; by centrifuge; by agglutination test; by inoculation; by tuberculin test; tuberculin; reaction; precautions, temperature before injection, exclusive of other illness, of parturition, abortion, heat, isolation, of hot building, of cold draughts, of hard floor, of faulty milking, privation of water, of change of food, of journey, of rude handling, of previous recent tests, of antipyretics, make special examination in unthrifty, test excluded animals later, danger of infecting through thermometer; technique; dose; time of injecting; identification and record of subjects; seat of injection; sterilization of syringe and skin; temperatures hourly or every second hour from 8th to 16th or later; typical reaction; accurate record of feeding, watering, milking or other occasion of hyperthermia or hypothermia; passing on the value of a rise; local swellings; chills; tremors; effect of test on general health of reacting and nonreacting animal; action on parturient cows; reliability of test. Relation of human to bovine bacillus; varying character of microbes generally, of tubercle bacillus in man; bacillus of man and bird interchangeable; tuberculosis in man and ox, similarity, coextensive, apparent exceptions, direct infection—man to cattle—cattle to man; encrease of tabes; experiments of Adami, Ravenel and Garnault; experiments on cold blooded animals; bearing of variations of susceptibility on sanitary work. Treatment: When admissible; hygiene; rich feeding; oleaginous seeds: cod liver oil; pneumatic cabinet; grooming; warm bath; medicated inhalations; sulphurous acid; chlorine; formaline; calmatives; carbonate of creosote; derivatives; streptococcic serum; air or oxygen in peritoneum; excision of tubercle; Prevention; Extinction in cattle; expense, supply of tuberculin and efficient veterinarians; appraisment; indemnities; vermin; disinfection; scheduling; control of purchases. Breeding healthy stock from infected; raising healthy offspring without sterilizing the milk. Removal of unthrifty and suspicious animals. Removal of animals showing objective symptoms, or, tuberculin reaction. Generally applicable measures. Hygiene of milk, butter, cheese, whey, oleomargarine. Hygiene of meat.
Tuberculosis may be acute or chronic, yet as seen in cattle, from casual infection, it usually comes on very slowly and insidiously and follows a chronic course. As the symptoms vary according to the organs involved it will be convenient to consider these in turn beginning with such as show the most diagnostic phenomena.
Pulmonary Tuberculosis. Though one of the most common and dangerous forms of the disease this may last for months or years without any suspicion on the part of the owner or caretaker of anything amiss. There may be an occasional cough, short, weak, dry, wheezing, perhaps repeated and roused by opening the stable door in cold weather, by leaving the stable for the cold outer air, by rising suddenly in the stall, by being driven on a run for a short distance, by drinking cold water or by eating dusty food. If driven for some distance, or put to draught work (ox) the subject blows more than the others. Sometimes even at rest, breathing is slightly accelerated. Yet the spirits may be as good, the eye as clear and full, the coat as smooth and sleek and the skin as soft and mellow as in health. Some such animals give as much milk, of as rich a quality, or, when put up to fatten, lay on flesh apparently as well as their healthy fellows. In favorable cases percussion may elicit circumscribed areas of dulness, and wincing or other sign of tenderness, and auscultation may detect crepitation or wheezing over the same points. By covering the nose and mouth with a sac or blanket the breathing is rendered more labored and the morbid sounds become clearer and more definite. The use of a stethoscope or phonendoscope may also render them more distinct. The morbid râles are more significant of tuberculosis if found in a number of isolated and circumscribed spots, with healthy respiratory murmur between, than if simply surrounding a single extended area of flatness as is usual in pneumonia. Much, however, stands in the way of success at this early stage. The heavy muscular and bony mass of the shoulder covers the anterior lobe and partially muffles the auscultation sound, while it renders percussion useless. The thick covering of the ribs in fat animals proves a serious barrier to successful auscultation and percussion. The varying plenitude of the abdominal viscera, and the rumbling, trickling, gurgling, and in the case of the rumen the crepitation of the contents, tend to complicate, obscure or cover up the pulmonary sounds. There is usually no appreciable elevation of temperature, or a slight rise of about one degree takes place at distant and uncertain intervals so as to render it useless for purposes of diagnosis.
When the disease is more advanced and the pulmonary lesions more extensive, the animals usually appear less thrifty on the same feeding, yet fat animals are habitually killed for food that show quite extensive pulmonary tuberculosis. With loss of condition, the coat loses its lustre somewhat, the hair becomes dry and stares in patches, and the skin loses its mobility and mellowness. The cough may be more frequent, perhaps paroxysmal under excitement, harsher, more short and broken, and either dry and husky or moist and gurgling, with a succeeding deep inspiration perhaps a moist râle. When the skin on the last ribs is pinched up between the fingers and thumb it is slower in flattening down to its normal smoothness, pinching of the spine at the shoulder or back, or it may be of the sternum, may cause wincing and even moaning, and the same may come of percussing the ribs smartly with the closed fist. There is now more decided evidence of flatness on percussion on the various affected points, and of abolition or lessening of the respiratory murmur, which is replaced by wheezing, or by bronchial blowing sound, heart beats and abdominal crepitation or gurgling, conveyed to the ear more clearly through the intervening consolidated tissue. The breathing may be slightly accelerated even at rest, and becomes distinctly so on exertion. The appetite fails somewhat and the secretion of milk lessens, or it may become more pale and watery. Chronic tympany occurring after meals occasionally appears, usually indicating tuberculosis of the glands along the œsophagus with pressure on that organ impairing eructation, and on the vagus nerve so as to impair nervous control. In connection with this there come on signs of generalization of the tubercle, as irregularity of the bowels, or enlargement or nodular induration of some of the superficial lymph glands, as the pharyngeal, prescapular, prepectoral, axillary, prefemoral, inguinal or mammary. Expectoration is usually abundant but it is difficult to secure it for diagnostic purposes since the moment it reaches the pharynx it is instantly swallowed, while any that may have been projected into the anterior nares is licked out by the pointed tongue. Nocard tried to secure this through a cannula passed in between the tracheal rings but with very little success. Others have introduced the hand into the pharynx, rousing the cough by tickling the larynx, and attempting to bring out the expectoration in the hand. When it can be secured its solid and opaque flocculi may be stained and examined for the bacillus, or it may be inoculated on a Guinea pig, intraperitoneally, to test its virulence. If there are open vomicæ or complex infection the breath is usually heavy and mawkish.
In the most advanced stages the symptoms are very characteristic. The subject is miserably thin and wastes visibly from day to day, the hair is dry and erect, most marked along the spine, the skin is scurfy, rigid, lousy, and clings firmly to the bones, the eyes are pale, deeply sunken in their sockets and bleary, the tears running over the cheeks, while a yellowish, granular, fœtid, and often gritty discharge flows from the nose, and dries in masses around the alæ. The cough is weak, painful, paroxysmal, and easily roused by pinching the back or breast or percussing the ribs. The breathing is liable to be hurried, even panting, and the animal may stand most of its time with nose extended to obviate the oppression that comes of recumbency. All the visible mucosæ are pale and blanched, and the pulse weak and rapid with every indication of anæmia. The temperature is usually raised to 104° or 105° F. and the milk secretion is completely arrested. Indications of generalized tuberculosis become more marked in the enlarged glands, diarrhœa, and clouded (purulent), or blood stained urine with microscopic casts, and even anasarca. The morbid sounds in the lungs have become a complex variety according to the nature of the lesion, blowing, wheezing, amphoric, friction, creaking, mucous, with the other bruits conveyed from adjacent organs. Death usually occurs in a state of complete marasmus, after months or years of illness.
Tuberculosis of the Abdomen. This usually affects the intestines, mesenteric glands, peritoneum, liver, spleen and pancreas, and has been known as tabes mesenterica. The generative organs also occasionally suffer, in which case, an early and rather persistent symptom is sterility, with a too frequent or it may be persistent desire for the bull (nymphomania). There is usually a steady loss of condition in spite of good feeding, the impaired functions of the intestinal mucosa, but especially of the mesenteric glands, liver and pancreas, interfering seriously with absorption and assimilation. The victims are therefore known as piners. While there may be more or less fever, highest in the evening, this is by no means marked, and cough and respiratory trouble may be entirely absent. Indications are not lacking, however, of digestive trouble. Slight tympany may follow meals, and the bowels are irregular, costiveness alternating with diarrhœa. If heavy feeding is resorted to, diarrhœa is the usual result, accompanied, it may be, by colic and tympany. There is a tendency to formation of pea or nut-like nodes under the skin of the flank, and Kleinpaul claims that the tubercles or vegetations on the rumen can be felt by manipulation of the left flank. Clearer evidence can often be had by rectal exploration, the tubercles and enlarged glands being felt on the rumen, in the knotted mesentery and in the sublumbar and subsacral region.
In case of uterine tuberculosis, the nymphomania may be supplemented by a purulent discharge, and rectal exploration may detect the tubercles on its surface, in the broad ligaments or even in the enlarged ovaries.
Great fœtor of the fæces may indicate ulceration of the mucosa, indigestion or impaired hepatic function.
For a great length of time the disease may be virtually confined to the mesenteric or portal glands, or even to the spleen, while the animal enjoys fairly good health. Again, in some instances, the subject may be fat and sleek, though the rumen, omentum or mesentery is to a large extent literally covered with tuberculous vegetations. The tuberculization of the intestines, mesenteric glands, liver or pancreas interferes far more with the general health than does even extensive peritoneal tuberculosis.
As the case advances it tends to generalization and winds up with the general symptoms predicated above of pulmonary tuberculosis.
Genital Tuberculosis in the bull is associated with nodular swelling of the testicle, epididymus or cord, hydrocele, and exceptionally tubercle on the penis, or in the prostatic sac.
Mammary Tuberculosis. This may be primary and circumscribed under direct infection through a trauma or by the milk ducts, but more commonly it is secondary to generalized tuberculosis. It may be a rather firm, uniform, painless swelling of one or two quarters (usually hind ones) without at first serious interference with milk secretion. As the disease advances, the follicles and ducts being invaded, an irregular knotted condition is developed, the milk becomes pale, watery, semi-coagulated and filled with bacilli, and the climax is reached in a densely indurated condition of the gland. From the first the mammary lymph glands, behind and it may be in front of the organ, become swollen, and they are finally indurated as caseation or calcification ensues. The superficial inguinal glands often participate.
Pharyngeal Tuberculosis. In this rather common localisation the retro-pharyngeal glands and those on the side of the pharynx especially suffer, though the parotidean lymphatic gland and the submaxillary often participate. Enlargement and induration of the tonsils and ulceration of the mucosa may be present. There is distinct swelling of the throat or displacement downward of the larynx, and the enlarged or hard nodular, perhaps even shrunken, glands may often be detected by manipulation. The nose is carried slightly protruded and a stertor or wheeze accompanies the breathing. A glairy liquid may run from the mouth or nose, and in this, bacilli may often be detected under the microscope. The retro-pharyngeal glands are very subject to softening and liquefaction, and in such a case an obscurely fluctuating swelling may be detected above the pharynx when the hand is introduced through the mouth.
This usually terminates in generalized tuberculosis, though it will often remain for a length of time the one appreciable localization.
Cutaneous Tuberculosis. The counterpart of tuberculosis verrucosa of man, this probably usually occurs by direct inoculation in a sore, yet the infection may reach the seat of lesion through the blood. It is usually represented by an irregular clustering warty growth, hanging more or less loosely from the skin and showing at points caseating centres. Bacilli may be recognized under the microscope.
Glandular Tuberculosis. Aside from the tuberculosis of the internal lymph glands already referred to, tubercles may form in any group of lymph glands, causing swelling, induration, fibroid degeneration or tuberculous abscess. Among these may be named the glands in front of the stifle or shoulder, at the root of the ear, beneath the zigoma, in the jugular furrow, the prepectoral, axillary, inguinal, etc.
Tuberculosis of the Brain and Meninges. Disorder of the cerebral functions occurring in generalized tuberculosis may be held to point to this disease. The earlier meningeal symptoms are often those of excitability, timidity, spasms, visual troubles, etc., merging later into vertigo, hebetude, paresis, unsteady gait, local paralysis and coma.
Tuberculosis of the Eye. This has been seen mostly as the result of experimental inoculation, with conjunctival and sclerotic congestion, corneal opacity, and the development of yellowish centres in the iris and choroid, from which the tubercle extends into the chambers.
Tuberculosis of the Heart, Pericardium or Pleura. Tuberculosis of the pleura is usually a concomitant of pulmonary phthisis, yet it may exist for a time independently, and its diagnosis presents serious difficulties. There may be tenderness of the intercostal spaces, a friction sound in case of raw granular surface or vegetations, creaking from false membranes or even flatness low down on percussion. If these escape notice, a short painful cough and slightly hurried breathing under exertion, in the absence of objective symptoms of lung disease, may lead to suspicion, but the true nature of the affection must remain in suspense. It usually leads to pulmonary or glandular (bronchial), and finally generalized tuberculosis.
Pericardial or Cardiac Tuberculosis is usually secondary and may be suspected when friction is synchronous with the heart sounds, when the heart beats or sounds are irregular or intermittent, or when the area of cardiac dulness is greatly encreased.
Tuberculosis of Bones and Joints. This is more common in calves and growing cattle, but may be present at any age. As affecting the vertebræ it causes stiffness and unsteady gait, perhaps what was looked on as a simple sprain causes persistent lameness in spite of treatment, and a point or area of tenderness on pinching is manifest. In the large bones and joints of the limbs, the cancellated extremities, or it may be a simple process with its inserted tendon or ligament, shows a firm, persistent swelling, and there is acute synovitis of the joint. In acute cases in calves the epiphysis may become detached from the diaphysis so as to make the limb useless. In the mature animal the enlargement and lameness may last for years without material change. The condition may be difficult to diagnose, in the absence of signs of tuberculosis elsewhere in the body, or unless the synovia, withdrawn through a sterilized nozzle, with antiseptic precautions, should show the presence of bacilli.
In young pigs, infected by the milk of the dam, there are general unthriftiness, stunted growth, emaciation and unhealthy skin, encrusted with a dark unctuous matter or scurf, as in chronic hog cholera. Temperature is variable on successive days, or times of the same day. Digestive disorder is manifested by slight colics, diarrhœa, vomiting, tympany and abdominal tenderness. The pig becomes pot bellied, with hollowness of the flanks in front of the iliac bones, and manipulation may detect the tuberculous bowels and mesentery in the form of a knotted mass.
Roloff describes a caseous colitis with ulceration of the mucosa, which is probably tuberculous.
Enlargement of the superficial lymph glands (pharyngeal, inguinal, prescapular) may be present. Traumatic infection of the castration sore and inguinal glands has been noted. As the disease becomes generalized, implicating the lungs, there is a dry paroxysmal cough and hurried breathing, becoming more oppressed on the slightest exertion. If quiet and thin enough for auscultation and percussion the usual morbid lung sounds can be heard. Unlike cattle, pigs are very subject to muscular and intermuscular tubercles, and as there is a general tendency to caseation, these are usually to be found as saccular cavities with soft, sometimes liquid, caseated contents. The bones and joints may suffer, as in cattle. The tonsils are usually enlarged and even caseous. The outer auditory meatus and the interior of the eye have been found affected. Cases affecting the brain were manifested by nervous disorder, rearing up on the fence, turning in a circle, spasms, rolling of the eyes, paresis and paralysis, often hemiplegic. When one or other of these indications of local disease is found associated with the general disorder of the lungs or bowels, in a herd fed on raw meat scraps, milk, or the soiled food of tuberculous animals, the evidence is strongly in favor of the local tubercle corresponding to the symptoms. It is noticeable that diagnosis by microscopic examination is difficult and uncertain because of the relatively very small number of the bacilli. In the mature pig the disease may be difficult of diagnosis without tuberculin, and a post mortem examination may be necessary to identify the disease in the herd.
Though not a common disease in the horse yet a large number of cases are on record, and accidental and experimental cases alike show that this animal is peculiarly receptive to the disease. The early symptoms depend on the location of the primary lesions, yet the general phenomena of debility, languor, early fatigue, unfitness for violent efforts, perspiration on slight exertion, irregular appetite, occasional rises of temperature and emaciation may usually be noted. The advance is usually slow, almost imperceptible, with periods of improvement and aggravation.
Some cases have appeared in the submaxillary and pharyngeal lymph glands with sore throat and were for a time mistaken for glanders (Ehrhardt, McFadyean). Others show a swelling of the appearance of cold abscess in the seat of the prepectoral glands (Johne, Röbert). One showed widely distributed lymph nodes and enlarged and indurated lymph glands (prepectoral, inguinal, etc.) with thickening of the intervening lymph vessels (Cadiot). This last suffered from bronchitis two months before. A number of cases reported by McFadyean showed special stiffness of the neck, with swelling and distortion of the vertebral joints, due to a tubercular osteitis and periostitis, and associated as necropsy showed with internal tuberculosis. Cases of this kind occurred in the practice of McConnell, Dawes, Insall, Malcolm and Hill, so that tuberculosis may well be suspected in cases of disease of the cervical vertebræ. In all of these cases post mortem examination, performed at once, or after a long delay, showed generalized internal tuberculosis.
When the chest is extensively affected, the symptoms are those of broncho-pneumonia or heaves (broken wind), there is hurried breathing with paroxysmal cough sometimes dry and wheezy, at others moist or mucous, a double lift of the flank in expiration, and a muco-purulent discharge from the nose, sometimes streaked with blood. Auscultation detects a varying force of the respiratory murmur at different points, with more or less wheezing. Blowing and other sounds conveyed to the ear through the solidified lung tissues are more rare or less marked. Percussion may show general resonance, encreased at emphysematous points, and diminished in small circumscribed areas, the seats of tubercle or consolidation. There are of course the attendant debility, inappetence, fever and steadily advancing emaciation. In some cases the enlarged tracheo-bronchial glands are seen to bulge forward between the two first ribs, and by the sides of the trachea. Stocking of the limbs is frequent.
Abdominal tuberculosis is most common in the young foal and when not secondary, may be due to feeding on tuberculous milk, especially in those brought up by hand on cow’s milk. There is debility, emaciation, anæmia, irregular appetite, digestive disorder, constipation alternating with diarrhœa, colics, pot-belly, falling in beneath the lumbar transverse processes, dry, harsh, scurfy skin and advancing marasmus. Rectal exploration will usually detect the enlarged sublumbar and mesenteric glands, and the simultaneous manifestations of disease of the lungs, superficial lymph glands, throat, or bones serve to identify the disease.
In the advanced stages of tuberculosis in solipeds polyuria is a frequent phenomenon (Nocard) tending to hasten the general anæmia and marasmus.
The patient often works for months or years but with gradually encreasing debility, which is soon fatal after the occurrence of generalized tuberculosis.
In estimating the nature of the disease, indications may often be drawn from the environment, feeding, etc. Nocard as the result of a careful study of the morphology and habits of the bacilli has shown that the more purely abdominal form of equine tuberculosis is near akin to that of the chicken, while the pronouncedly pulmonary form resembles the human type. McFadyean on his part adduces a number of cases of tuberculosis in horses that had been fed largely on cows’ milk, a most significant fact considering that such a ration is rare for this animal, and that few horses contract tuberculosis casually. Exposure therefore to the sputa of man, of the nasal or bowel products of birds or to the milk of cows, may suggest the probability of tuberculosis in a horse with chronic anæmia, debility and wasting.
The discharges from the nose of the affected horse are more available than those of cattle for examination and experimental inoculation, yet in many occult cases the diagnosis by tuberculin is the only reliable resort.
The tubercles have been usually found post mortem in these animals or as the result of experimental inoculation, and symptoms have not been well recorded. They follow the same order as in the ox, weak husky cough, wheezing and other râles in the lungs, disorders of the digestive organs, swollen lymph nodes and glands, and caseated products in those that were of some standing. I have found these latter especially, in the region of the throat in high bred rams kept in confined buildings or yards and highly fed to prepare for letting or sale. These lose in vigor and activity and scrofulous swellings form on the neck, head or elsewhere and become rapidly caseated. In German abattoirs tuberculous sheep proved 0.1 to 0.15 per cent. In Saxon goats the percentage was 0.6.
These follow in the main those of consumptive cattle. As the infection generally enters with food, the early symptoms often point to disease of the throat and alimentary tract, while the later ones involve those of the respiratory organs as well. Impaired and capricious appetite, debility, early exhaustion under exertion, emaciation, sunken pallid eyes, apathetic expression of the face, lack of life and gaiety, a knotted feeling of the abdomen if the region is flaccid, and a tense fluctuating sensation if ascitic, with usually enlargement of the superficial lymph glands are noticeable.
When the chest becomes affected there is the hurried breathing, quickly encreased by exertion, panting, paroxysmal cough, wheezing, and the various morbid râles in the chest, crepitant, friction, creaking, blowing, cavernous, mucous, etc. On percussion, flatness is detected in limited areas in a number of centres. Expectoration is usually promptly swallowed and can only be secured with difficulty for examination.
When tuberculous sores and fistulæ occur in the region of the throat or elsewhere, the evidence is patent and the bacilli can easily be found in the discharges.
In cats the course and symptoms do not materially differ. In both animals the history usually shows the connection of house life and the habit of eating after tuberculous persons.
In the gallinaceæ there may be inappetence, vomiting, diarrhœa, with hurried breathing, sneezing, and the general phenomena of debility, weakness, advancing emaciation and anæmia, the comb and wattles becoming pale and flaccid and the visible mucosæ bloodless. The eyes are sunken and lack lustre, the head sinks, the wings and tail droop, and weight is steadily lost. When the bones and joints of the legs and wings are involved the local swellings and distortions are visible indications of the trouble.
In parrots these local swellings and particularly the horn-covered vegetations on the face and around the beak are characteristic.
Canary. Tuberculosis is common in the canary, contracted, as in the parrot, from man, with whom alone the caged bird comes into dangerous contact. The interchange of the disease between pet birds and their owners would demand the exclusion of such from the rooms of consumptives, and a careful watch for indications of disease of the air passages with marasmus, that the bird may be disposed of before it has become a source of danger.
It is needless to repeat the various symptoms of tuberculosis according to its different seats and the degree of its extension in the animal body. In cases in which the indications are slight, greater importance may be given to them through the knowledge of the existence of more advanced or decided cases in the same herd, or the necropsies of animals taken from it. Yet in the average herd it is safely within bounds to say that three fourths of the affected cattle will escape condemnation if we employ objective symptoms alone. In one herd of seventy head, in which the tuberculin test condemned twenty-four head (being 50 per cent. of the mature animals), I left the examination after slaughter to the veterinarian of the A. J. C. C. who was at the time skeptical as to the value of the tuberculin test. He wrote me afterward of his surprise at finding every one of the twenty-four condemned animals tuberculous, when not one of them had shown symptoms by which he could recognize the disease in life. This is no exceptional case, and may be advanced rather as a typical example of the ordinary infected country herd.
Microscopic detection of the bacillus in the expectoration may be successful in the horse with pharyngeal or pulmonary tuberculosis, but fails in those forms that affect the other internal organs. It is all but useless for the expectoration of cattle and dogs. When there is cutaneous tuberculosis or a tuberculous fistula this is much more valuable, and it is especially useful in dogs and parrots.
The precipitate in the centrifuge will often show the bacilli that are present in milk, but in very many cases of tuberculosis the bacilli are not present in the milk.
The centrifuge used on the urine may also succeed when kidneys, bladder or prostate are affected, but the bacilli are rarely found in the absence of disease of these organs. The smegma bacillus is a source of fallacy.
The serous effusions in the affected serosæ (pleura, peritoneum, pericardium, synovial cavities) may also be centrifuged and the presence of the bacilli revealed.
The agglutination test of Arloing and Courmont though often giving positive results, (95.5 per cent. in pulmonary tuberculosis, 50 per cent. in surgical, Arloing and Courmont; 40 per cent., Knopf; 25 to 50 per cent., Lartigan); yet proved too unreliable, and frequently gave positive results when tuberculosis was absent. The best medium for cultures to be so used is 6 per cent. glycerine bouillon, and the age of the tuberculosis culture 8 to 12 days. One part of fresh blood serum of the suspected animal in a sterilized capillary tube is added to ten parts of the bacillus culture, and the tube placed in an oblique position. In 2 to 24 hours a fine sand-like material precipitates along the sides of the tube, and the microscope shows the bacilli in clumps, absolutely still without even Brownian movements. Gallemaerts found that it proved very satisfactory with the serum of Guinea pigs after three days from intraperitoneal inoculation, was less marked after inoculations subcutem, and that in man the agglutination appeared in influenza and pneumonia in the entire absence of tuberculosis. Such an uncertain test cannot be utilized in veterinary sanitary work.
Experimental inoculation with milk, expectoration, morbid discharges, the scraping of nodules, etc., is much more searching, and will detect more cases than the microscopic examination. But it fails entirely in cases in which the milk of unquestionably tuberculous animals is free from bacilli, or in which the local nodule or discharge tested is itself free from tubercle. It is a test of the local lesion and not of the entire animal system.
In choosing a subject for inoculation, the first consideration is that it must come from a healthy stock and be itself free from tuberculosis. Next, it must be of a species actively susceptible to the habitual tuberculosis of the animal from which the inoculated matter is taken. Thus for man, ox, dog and parrot, the Guinea pig is especially appropriate, while for gallinaceæ and horses, the rabbit is to be preferred. Inoculation is usually made into the peritoneal cavity.
As a period of two or three weeks is usually necessary to allow of an extensive development of tuberculosis, the method must be too often discarded on account of the delay in obtaining results.
Tuberculin test. Many stock owners still entertain an ignorant and unwarranted dread of the tuberculin test. It is quite true that, when recklessly used by ignorant or careless people it may be made a root of evil, yet as employed by the intelligent and careful expert it is not only perfectly safe, but it is the only known means of ascertaining approximately the actual number affected in a given herd. In most infected herds, living under what are in other respects, good hygienic conditions, ⅔ or ¾ are not to be detected without its aid, so that in clearing a herd from tuberculosis and placing both herd and products above suspicion the test becomes essential.
Tuberculin is the bouillon in which the tubercle bacillus has been grown, charged with the toxic products of its growth, but which has been raised to a boiling temperature to destroy all germ life, and from which the dead germs have been removed by passing it through a porcelain filter. When a physiological dose of this has been injected, subcutem, into the suspected animal, it has no effect on the non-tuberculous, while in the tuberculous it produces, in the course of the next 24 hours (usually from the 8th to the 16th), a steady rise of temperature by 2° F. or more, followed by a slow subsidence to the normal. This may last for from three to ten hours in different cases.
Among the precautions may be named:
1. The temperature of the animal is best taken at intervals, or at least, morning, noon and night, on the day preceding the injection to see that the animal shows no habitual rise at any time of the day. Yet in busy field work the one night temperature taken just before injecting will rarely fail to give a satisfactory normal as a standard for the animal. Any quotidian rise almost invariably reaches its climax at night.
2. The subject must be in good general health. If there is present in the system any concurrent disease it may undergo an aggravation within twenty-four hours and give a rise of temperature that will be mistakenly set down for tuberculosis. At the very start, therefore, it is important that the general health of the subject should be first assured by a critical professional examination. If some other disease is present the tuberculin test had best, as a rule, be delayed until that has subsided, while if tuberculosis is found the test will be superfluous.
3. The subject must not be within three weeks of parturition, nor about to abort. In many cases, though not in all, as preparations are made for calving, the system becomes unduly susceptible to the presence of tuberculin and that agent will cause a rise of temperature, though no tuberculosis is present. Unless this source of error is carefully guarded against the most valuable cows in the herd may be condemned unjustly.
4. The cow must not be within three days of the period at which “heat” would naturally occur. Under the excitement of œstrum the body temperature usually rises two or three degrees, and if tuberculin has been used this rise may be attributed to tuberculosis and a sound animal may be condemned. Nor is it always enough that the animal is supposed to be pregnant. Abortions sometimes take place unexpectedly and unknown to the owner. If, therefore, a cow under the test and which is not well advanced in pregnancy should show a rise of temperature it should be at once ascertained whether the animal is not in “heat.” If symptoms of “heat” are found she should be set aside along with any calving cows to be tested again when such a source of error is no longer present.
5. The tested animal must not be exposed to a hot sun in a closed area. In excess this will cause heat apoplexy, and the fever heat which ushers this in, may easily be mistaken for the indications of tuberculosis.
6. Cattle taken from pastures must not be enclosed in a hot, stuffy stable. While they must be tied up to allow of the temperature being taken at short intervals, coolness and ventilation should be secured in summer by a sufficient air space and the requisite ventilating openings.
7. Exposure to cold draughts between open doors and windows, or to wet or chilly blasts out of doors should be carefully guarded against. A chill proceeding from any source and alike in the presence or absence of tuberculin causes a rise of the internal body temperature.
8. Heavy cows unaccustomed to stand on hard boards may have a rise of temperature in connection with resulting tenderness of the feet. One must avoid hard floors on the day of the test or make examination of feet and allow for attendant fever.
9. Omission of the previous milking or a change of milker and consequent retention of part of the milk will raise the temperature of a nervous cow, and in careless hands secure an erroneous condemnation.
10. Privation of water at the regular time will often cause rise of temperature especially when on the dry feeding of winter. I have seen a general rise of two degrees and upward from the delay of watering for a single hour, while after watering the temperature went down to the normal and remained so. Water always tends to a temporary lowering of temperature but in the presence of tuberculosis it soon rises again.
11. Change of food is liable to produce a slight indigestion and rise of temperature. This should be avoided as far as possible, and when a herd is taken up from pasture for the test, it should have grass, ensilage or other succulent food.
12. Cattle just from a long journey by road or rail, or other cause of violent exertion are liable to have an elevated temperature from the leucomain poisoning. Such should be left at rest until the transient fever shall have subsided.
13. Violent handling of nervous cows in taking the temperature must be carefully avoided. The operator who cannot handle them gently is not fit for this work.
14. There must be evidence that the animals have not been repeatedly tested at short intervals shortly before. In a number of instances I have found a proportion of the cattle irresponsive to tuberculin, though a post mortem proved the presence of tuberculosis. Unscrupulous men, wishing to sell on a guarantee, can avail of this in animals so unaffected by the test.
15. The operator must have absolute control, even of the feeding and watering of the animals on the day of testing. Otherwise the rise of temperature may be prevented by a liberal use of antipyretics and a false guarantee may be secured.
16. An unthrifty animal, having general symptoms suggesting tuberculosis, must be subjected to the most critical examination in addition to the tuberculin which in such animals often fails to cause hyperthermia. Fortunately in such animals the tubercles are usually numerous and extensive enough to be discovered through objective symptoms.
17. Animals excluded from the test by reason of some individual unfitness at the time (parturition, œstrum, abortion or any other disease) must be marked and held for the test later after such disqualification shall have passed.
18. The operator must bear in mind the possibility of transferring other diseases from animal to animal, by contact, by the use of the same hypodermic needle on two in succession, and above all by the clinical thermometer. Diseases like contagious abortion, which present no obvious symptoms in the intervals, are especially liable to be carried in this way, and instances of the active extension of this after a test, have come under my notice. The operator should always enquire carefully as to the existence of abortions and sterility in the herd, put the aborting animals by themselves, using a special thermometer upon them, and carefully washing the hands before going to other cattle. It is well further to clean the thermometer after each animal and disinfect it with carbolic acid solution (5:100).
Dose of Tuberculin. Of the usual American preparation 2cc. (30 drops) is adapted to a cow or ox of 1,000 to 1,200 pounds. For larger and smaller animals a moderate encrease or reduction must be made, yet a considerable latitude is allowable. The new-born calf will take five drops and the animal of 700 pounds 25 drops.
Technique of the Operation. Lapses are so easily made when dealing with a large herd and are so dangerous that a regular plan should be systematically followed. The following will be found simple and convenient:
1. Inject the herd at 10 or 11 P. M. to secure a good rest and be fresh for the rise of temperature early next morning.
2. Before injecting have the subjects arranged in order and record them by name or other means of identification, with age, sex, breed, weight, pregnant or not, past or prospective date of calving, abortion, indications of disease, temperature taken just before injection and appropriate dose.
3. Inject into the loose connective tissue on the side of the neck, the animal being held by the nose, if necessary, by an assistant.
4. Use a syringe which has not been employed for any infectious products, and see that it is thoroughly cleansed and disinfected by boiling or by filling it with a carbolic acid solution (5:100).
5. After drawing the appropriate dose into the syringe, wipe the nozzle and dip it in strong carbolic acid before inserting it into the skin. This safely disinfects any virulent matter that may be lodged on the surface of the skin, and obviates those infected swellings and abscesses that have been a cause of complaint by stock owners.
6. When the nozzle is withdrawn from the skin, wipe it and dip it again into the strong carbolic acid to prevent any risk of infecting the tuberculin into which it is to be plunged.
7. The nozzle is much more easily inserted in the skin if the latter is pinched up so that the needle will transfix it at a right angle, instead of passing through a greater amount of the dense tissue because of the oblique direction. An excited animal with a thick, tense hide and a contracted panniculus muscle will offer serious obstruction which lessens greatly as the subject gets over its excitement and the muscle relaxes.
8. Temperature should be taken at 6 or 7 A. M., eight hours after injection of tuberculin, and every two hours thereafter, until the sixteenth hour.
9. If any subject shows no rise of temperature until the 16th hour after injection, its examination may be discontinued, but if it shows a slight rise toward the 16th hour it should be continued until it has shown a distinct reaction with steady rise and fall, or until, without such distinct reaction, the temperature descends to the normal.
10. If one has shown a distinct reaction but is still rising at the 16th hour, it should be continued till it begins to fall. The typical reaction is one in which the rise and fall are both gradual, and extend over a number of hours.
11. In recording the temperatures, there should be noted the exact time of each feeding, watering and milking, or any other condition (change of weather), which may in any way affect the heat production or radiation.
12. In old, emaciated animals and in second or third tests, Pearson uses twice the usual dose of tuberculin or more.
Tuberculosis Reaction. With slight variations different operators make their estimate of tuberculosis reaction on nearly the same general basis. A rise of 2° F. over the highest temperature of the day or days before, in the absence of any other appreciable cause, and provided that the elevation has followed the tuberculosis type of gradual rise and fall, is held to condemn. If, however, this rise does not exceed the normal average, if the temperature before injection did not exceed 100° and that after injection 102°, the case may well be held in doubt and reserved for re-testing. If, on the contrary, the initial temperature of the animal was 103°, and there was, between the 8th and 16th hours, a gradual typical rise and fall, reaching 104° or a little over, in the absence of any other cause for this, the subject would be condemned. Cattle having an initial temperature of 103° or above are not favorable subjects for the test, except in the case of calves in which the temperature is normally higher and the reaction must reach a higher point. In all cases of doubt it is well to hold for a second test, unless urgent sanitary considerations demand that a herd should be freed from the infection in short order. Then it may be better to risk a single error, with the concurrence of the owner, than to leave a possible centre of infection in the herd.
Local swelling in the seat of injection may be charged to lack of antiseptic care, or the presence of septic germs in the system of the animal prior to injection.
A chill during the period of reaction is not uncommon, especially in cold weather, or in a draught of cold air. The coat may stare along the spine in patches, or generally, tremors may be seen on the body or limbs, and a clammy coldness invades the ears and horns, and especially the points of the hocks and ischia. The back is sometimes arched and the feet drawn together somewhat.
In the absence of any source of excitement the head may be less elevated, the ears lopped forward or drawn back, and even the eyelids may droop somewhat. These phenomena may last for a few minutes or for an hour or two.
In testing other genera consideration must be had of the different normal temperature (horse 99.5°, dog 98.5°, sheep or pig 103°, bird 106°), and the varying susceptibility to tuberculin, the Guinea pig requiring a maximum dose relatively to its size and man or horse a minimum.
Effect of Tuberculin Test on the Later Average Health of the Animal Reacting. The transient fever and reaction on the day after injection modifies the milk secretion temporarily to a certain extent in ratio with the hyperthermia. The consensus of veterinarians of the largest experience, and the voice of the International Veterinary Congress at Berne in 1895, oppose the doctrine of any continuous effect on the health even of the tuberculous. Yet in the case of Governor Morton’s large herd of Guernseys a careful record of temperatures showed that for weeks after the test the reacting animals presented oscillations which were not shown before, and which were not found to occur in the sound animals. In the activities of sanitary work such indications are easily missed.
Effect of Tuberculin Test on Sound Animals. In 1894 I tested this on a number of thoroughbred Jersey and grade cows, injecting them six times at intervals of from five to fourteen days. It led to no appreciable change of the general health as shown by the temperature, breathing, pulse, yield of milk or its quality. Careful analysis was made of the milk at each milking, and in two animals soundness was attested by post mortem examination. Similar tests made by the Bureau of Animal Industry and others led to the same results. Cows in which the yield of milk was on the gain continued to encrease in the same ratio as those that had not been injected, and those in which it was on the wane showed no more rapid decrease. The butter fats and total solids showed no variation more than appeared in the healthy.
Action of Tuberculin on Parturient Cows. The testimony of Bang, Eber and Pearson, based on a very extensive experience, would indicate that the tuberculin test is not forbidden by the parturient condition. Eber concludes that unless the initial temperature materially exceeds 39.5° C. (103° F.) the parturient state is no barrier to successful testing. My own experience, on the contrary, is that a considerable proportion of parturient cows give a reaction when the initial temperature did not exceed 103° F., and when no sign of tuberculosis could be found. As an example, a cow in high condition, with an initial temperature of 102.8° F., rose gradually from the eleventh hour after injection and reached 106.3° by the eighteenth, a rise of 3.5°. From the record she was not due to calve for three months, but a fortnight later, when already killed and laid open, she showed all the signs of parturition, a fully matured calf, and not a trace of tubercle. This is far from unusual, and I am convinced that many errors will be avoided by refusing to condemn parturient animals or those within a couple of weeks before or after parturition on the tuberculin test alone.
Reliability of the Tuberculin Test. Even in the most careful hands the tuberculin test cannot be held to be infallible. A certain very small proportion of cows react without the recognition of any tubercle post mortem, some because of other bodily conditions, like parturition or abortion, but in skilled hands these may be ignored in ordinary sanitary work. Pearson claims to have had but 8 such cases in 4400 cows that gave a typical reaction. He suspects that some of these even had undiscovered tubercle, and Nocard thinks that all such cases are to be explained in this way. On the other hand a very few really tuberculous animals fail to react, some in connection with advanced disease, some because of repeated previous testing, and some because of the introduction of antipyretic agents into the system, but such cases can either be detected and controlled or are so infinitesimal in numbers, that they can be safely ignored in sanitary work. In skilled hands, the tuberculin test will show at least ⁹⁄₁₀ths of all cases of tuberculosis, when other methods of diagnosis will not detect ⅒th. See above case of herd where objective symptoms showed nothing, yet tuberculin condemned half the mature cattle, and post mortem confirmed this, the skeptical veterinarian being judge.
The Relation of the Bacillus Tuberculosis of Man to that of Cattle. On the discovery of the bacillus tuberculosis it was largely assumed that it was the same in all tuberculous animals, in all organs and in all circumstances. But it was soon found that the bacillus of chicken tuberculosis differed materially from that of the mammalian, that it could be inoculated only with difficulty on cattle or Guinea pig, as could that of the latter on the bird. The bacillus of the chicken found a most receptive home in the rabbit and horse, and was more easily started in artificial culture in glycerine bouillon, than was that of man or ox. But presently it appeared that the affinities and disparities did not end here. The bacillus from man or ox led to much more pronounced lesions in Guinea pigs than in rabbits, and the abdominal bacillus of the horse was inoculable on the chicken. Both horse and parrot proved receptive to the bacillus from man. Swine, like Guinea pigs showed a receptiveness to the bacillus of man or ox. The bacilli from the sputum, open tuberculous sore, or bones of man showed less virulence for Guinea pigs and rabbits than did those from tubercles in the human lungs and liver. The bacillus from the ox showed a greater virulence toward rodents and other small animals than did the bacillus from man. The bacillus of human sputum inoculated on the ox did not habitually cause generalized tuberculosis, but oftentimes a local tubercle or group of tubercles, and sometimes the inoculation wound healed without permanent lesion. These last points were seized upon to sustain a doctrine of probable duality for the microbe of tuberculosis, but if duality it was quite evident it could not end there, but must be extended to multiplicity, each small group of genera having a tubercle bacillus peculiar to itself. Those who thought their interest lay in arresting all sanitary control of tuberculous cattle and their products, became urgent in opposition to active government measures, demanding mathematical proof of the infection of man from cattle, under conditions that would exclude the remotest possibility of the introduction of infection from another source. The clearest and most abundant circumstantial evidence would not suffice, they must have direct experimental inoculation under conditions of precaution against outside germs, which were practically impossible in any community, conveniently ignoring that such inoculation, if successful, would have amounted to manslaughter, and that no such experimental evidence has been had, or can be had, of any of the deadly diseases of man. Infection by exposure and accidental inoculations can be had in abundance, just as they can in tuberculosis, but never under the rigid precautions which would exclude the possibility of extraneous infection.
The subject has assumed such importance that I may be excused for introducing a portion of my paper read before the New York State Medical Society in 1900.
1. This Variability is Common to Microbes Generally. Certain bacilli, like those of anthrax, grow in the living body as rods only, but become long filaments in given artificial media. They produce no spores in the living tissue, but do so readily in the carcass or soil. Transferred from ox to ox they are generally fatal, but if grown for several generations in Guinea pigs, and then transferred to cattle, the resulting disease is slight (Burdon-Sanderson, Duguid, Greenfield). Rabies passed from dog to dog is almost constantly fatal, but if passed through the ape and then back to the dog it is comparatively harmless (Pasteur). In both these cases the inoculated animals become immune from the more virulent germs, showing that they have passed through the actual disease in an unusually mild form. The later system of Pasteur is founded on this same general truth, as are also the methods of lessening the pathogenesis of germs by subjecting them to compressed oxygen, to graduated heating, to an altered chemical condition of the culture medium, to antisepsis, etc. For a time such weakened cultures often retain their lessened pathogenesis, even through a succession of cultures in a susceptible animal body, acting as if the germ were indeed a distinct species. But it might well have been considered that a microbe which had changed its aptitudes in a given environment could presumably revert to its original habits under the incentive of a suitable medium. And this is precisely what does take place. Pasteur has shown that the less potent rabic virus becomes more potent when passed several times through the body of a rabbit, and that the weakened anthrax germ acquires greater force when passed through a series of small birds or newly-born mammals.
To come to tuberculosis, Trudeau tells us that a culture of bacillus tuberculosis from man inoculated on the rabbit, and then cultivated for two years in vitro, becomes much less destructive to Guinea pigs, and that after six years of such artificial culture all the Guinea pigs inoculated with it live for many months, some for two and a half years, and some even recover. The usual life of the Guinea-pig after inoculation is seventeen days.[3] All of our zymotic diseases have in a similar way cycles of malignancy and benignancy. For a series of years measles, scarlatina, diphtheria, smallpox, or grippe have an unwonted mildness, and, again, one or another merges into a cycle of extreme and fatal malignancy. Rinderpest on the steppes of Asia is comparatively harmless to the native stock, but among outside cattle imported into the steppes or attacked in their native lands it is habitually fatal. Texas fever is mild among the indigenous cattle in the Gulf States, but very deadly to Northern stock. Glanders is not at all fatal to horses of the plains, the Rockies, or the Sierras; but it becomes redoubtable when these horses carry it to the Eastern seaboard, and still more so in Western Europe. It is a common experience to see a malady transformed through the effects of heredity or acquired immunity, through environment or the temporary mitigation of virulence in the germ; and again we see the same disease, no longer restrained by such inhibitory conditions, bursting forth as a malignant and deadly plague. We have, therefore, no warrant for the hypothesis that a pathogenic germ which, under given conditions of life, has lost in pathogenesis, but not in vitality, should continue forever to exist as a harmless microbe.