SYMPTOMS OF TUBERCULOSIS IN THE HORSE.
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.