The occurrence of the rheumatoid affection as a complication of influenza and contagious pneumonia in the horse, usually appears not earlier than 15 days after the outset of the pulmonary affection and may be delayed, according to Palat, for 102 days. Palat who had excellent opportunities for observation in army horses found that about one in ten was the ratio in which the rheumatic affection followed these pulmonary diseases.
The pulmonary lesions in these affections are essentially those of uncomplicated influenza, or contagious pneumonia.
Cerebro-Spinal Lesions. Nervous disorders are occasionally seen in rheumatism in man (dullness, prostration, delirium, coma, spasms) and traced in different cases to hyperthermia, congestion, exudation, embolism and toxins. In a few cases in the horse, cerebral complications have been observed. Olivier saw a horse with lachrymation, closed eyelids and hot, tender forehead, which showed at the necropsy articular inflammation, and sanguineous effusion in the cranium, encephalon, frontal and maxillary sinuses and ethmoid cells. Jacob records two cases (mare and horse) in which rheumatism was complicated by meningo-encephalic congestion but without necropsy as both recovered.
Digestive system. In man rheumatism has been exceptionally preceded by pharyngitis, dysphagia, and diarrhœa. In the horse Haycock has seen concurrent congestion of the pharyngeal mucosa, Olivier congestion of the stomach and intestine, and Jacob diarrhœa and abdominal pain, Leblanc and Palat record cases of peritonitis accompanying articular rheumatism in the horse.
SYMPTOMS OF ACUTE ARTICULAR RHEUMATISM IN THE HORSE.
Chill, hyperthermia, lameness in fetlock, hock, knee, shoulder, stifle, hip, elbow, tendons, sheaths, bursæ, bilateral, shifting, swelling, heat, tenderness, decubitus, joint semi-flexed, pain on extension or flexion, signs of cardiac disease. Course: rapid to recovery, improvements and relapses, metastasis, debility.
The attack is usually sudden and marked by a slight chill, shivering or staring coat with hyperthermia and lameness. The temperature may vary from normal to 107° or 108° F. in severe attacks. In many cases the fever and lameness appear simultaneously, the former being in ratio with the extent and severity of the latter, but not infrequently the elevation of temperature precedes the articular symptoms, and then it is to be considered as concurrent with the internal lesions—cardiac, pericardial or otherwise. In other cases the articular lesions and lameness precede by several days the appearance of the fever. So far as we know the fever never antedates the occurrence of some local lesion, external or internal.
The joints affected are very varied. The fetlock is the most frequently attacked, but some of the other larger joints, the hock, knee, shoulder, stifle, hip and elbow are often involved or exclusively affected. The adjacent tendons and their synovial sheaths are very often implicated; the attack is very prone to show a bilateral symmetry, the same joints (right and left) on the corresponding fore or hind limbs, suffering at once, or, as in the case of the fetlocks, all four are simultaneously attacked. A joint that is weak by reason of previous injury or disease is especially liable to suffer, and is then less likely than joints that had been previously healthy to undergo speedy improvement. When the symptoms wander from joint to joint or from joint to muscle, or fascia or tendon, the disease in its earlier seat seeming to undergo almost complete resolution, while it advances with great intensity in the newly affected joint or part, the occurrence is highly significant. These transitions often take place with great rapidity. Thus the centre of suffering may shift from one joint to another in an hour, (Megnin, Cadeac), or from a limb to the loins in a quarter of an hour (Lewis). The fact that the inflammation remains fixed in one or several joints, is not, however, proof of the absence of rheumatism. A joint with a primary weakness or injury may remain the seat of disease through even a chronic rheumatism.
The affected joint is usually swollen, hot and tender; the tenderness being as a rule greatest where the capsular ligament is pressed upon. These symptoms are very evident in joints that approach the surface, and obscure in such as are thickly covered by muscle (shoulder, hip). The swelling is soft, or tense and elastic (especially over the synovial membrane), or œdematous and pitting on pressure. On white skins sparsely covered by hair there is marked redness and congestion, the veins standing out prominently and the arteries above the joint pulsating strongly. When the tendinous sheaths are involved, they stand out as elastic lines following the course of the tendons, and with more or less pasty swelling adjacent.
In some cases, however, the swelling may be entirely absent, and the trouble is to be located only by the local tenderness and pain during motion.