Urine may be passed freely or the bladder may be paretic so that it must be emptied with the catheter. In severe cases the urine is of a high density and of a dirty brownish gray, red or almost black color. It contains no blood clots, nor blood globules, but granular hæmoglobin, tyrosin and other waste products contribute to produce the reddish color. In some instances there is an abundant metalbumen which renders the liquid glairy, causing it to fall in fine threads or films. Urea is usually present in great excess. Hippuric and even uric acid are usually present but not in excess. When the disease has advanced to nephritis the albuminuria is complicated by the presence of casts of the uriniferous tubes, renal epithelium, white and even red blood globules.
During the violence of the attack there is no disposition nor leisure to eat, but when the more violent symptoms abate appetite is usually manifested. There may be more or less paresis of both bowels and bladder, so that neither fæces nor urine is passed yet in other cases both are discharged spontaneously.
The senses are preserved, excepting in the case of the affected muscles and the integument which covers them. There may, however, be more or less dullness and stupor in certain cases from poisoning of the cerebral centres by the poisons circulating in the blood.
Mild Cases. In the mildest cases there is stiffness and lameness in one, or less frequently in both hind limbs, coming on when put to work after a period of idleness, and not associated with any appreciable lesion of the limb in question. There may or may not be hardness and swelling of the gluteal or other muscles of the quarter or loins. This has the appearance of rigidity or spasm but may be primarily due to œdema or exudation into the substance of the muscle. In some instances the muscles of the breast, shoulder, or forearm are the seat of the trouble. Muscular trembling and perspiration may be present and if the urine is examined, it is often found to be glairy, or charged with urea, and allied nitrogenous products. These cases are not benefited by local applications, but they recover (temporarily) under rest and above all under active eliminating treatment. Under gentle and progressive exercise too they improve and get well. They recur, however, with great readiness under a rich nitrogenous diet and a temporary rest followed by sudden exertion.
Between the mildest and gravest cases there are infinite gradations of severity, one-third to one-half of the worst cases usually terminating fatally, whereas the mildest are always amenable to treatment.
Progress. The course of the disease depends on the severity of the attack but also, in no small degree, on the good judgment of the driver. Cases that develop with great suddenness, and apparently with extreme severity may subside spontaneously if the animal is placed in a condition of absolute rest. If, however, we can secure rest of the muscles of progression only, while the breathing remains rapid and labored, improvement is unlikely, as the system continues to receive large accessions of the toxic products. When the patient is down and unable to rise, the enforced rest may be beneficial, but too commonly, the greater effort with which breathing is carried on in the recumbent position, and the frequent ineffectual struggles of the limbs prevent the requisite muscular quietude.
In some cases, and especially in the mildest, recovery may seem to have been effected in a few hours, and in others it will be seen in twenty-four or forty-eight hours, while in still others the paresis and helplessness may continue for a week and yet be followed by recovery. In these cases appetite may be retained in greater or less degree, but the intestinal peristalsis is usually weak and imperfect, the fæces small in quantity and dry, and the bladder atonic so that the urine may have to be drawn off with the catheter. It usually retains the deep red color, or improvement may be heralded by a change to a dirty grayish hue. If, however, it shows an excess of albumen, cylindroid casts entangling renal epithelium and white or red globules it will indicate the access of diffuse nephritis and a prolonged or even a fatal illness.
When control of the limbs is not restored at the end of a week, the paretic muscles usually undergo marked and rapid wasting, which may last for months or years. This is especially common in the case of the patellar muscles (muscle of the fascia lata, triceps extensor cruris) in which the atrophy may become so extreme that the skin covering the inner and outer sides of the thigh may be brought virtually in contact in front of the femur. This entails an almost complete inability to sustain the body on the hind limbs. When atrophy is less extreme, there is only a weakness, stiffness, or swaying or staggering on the hind limbs in progression.
In fatal cases death may occur early in connection with the violent struggles, the excited breathing, pulmonary hypostasis and congestion, a cyanotic hue of the visible mucous membranes and a gradual increase of stupor. Though delayed for several days, there is a continuation of the muscular struggles, and the labored breathing; the red or glairy character of the urine persists or is exaggerated; the nervous irritability increases, with muscular trembling; and cyanosis, or stupor increases until death.
The mortality is always high in the severe forms of the disease, the deaths ranging from 20 per cent. upward.