Darkness usually coincides with confinement and it is noteworthy that deep sea fishes, living in comparative darkness, have usually cartilaginous skeletons.
Infection. Certain facts seem to point to a direct infection, as coöperating with the debilitating conditions above named. The advent of the disease in England about 1700: its frequency in English swine on the European continent (Schneidemühl); and its enzootic prevalence in different parts of America, give seeming support to the doctrine.
Dr. W. L. Williams has seen it appear on an Illinois farm twenty years after reclamation from virgin prairie, prevail for ten years and then disappear. There was a remarkable coincidence of recurrent ophthalmia, and disease of the bones and joints (navicular disease, spavin, splints, ring bones, etc.).
In most of these cases the trouble occurred on low, damp or impervious soils, agreeing with rickets in children, which avoids the Alps or hilly districts, and abounds in valleys or bottom lands.
Symptoms. The colts show a lack of thrift and though there may be no lack of growth or size, they have a rough coat, a poor development of the neck, arching of the back and drooping pelvis. The chest may seem to sink between the scapulæ. They move stiffly with swaying of the limbs, or even staggering and are easily wearied or lacking in endurance. They lie a great portion of their time or even persistently, refusing to rise. When up they do not hold the limbs plumb, but allow them to deviate one way or another in an unsightly way. There is liable to be swelling of important joints of the limb, (knee, hock, stifle, fetlock), which are tender to pressure and kept partly flexed. The ends of the ribs are often enlarged. Bending of the long bones (tibia or radius), and deviations of the back or sternum from the straight line are significant. Thickening of the ends of the bones, or in the region of the epiphyseal cartilages are largely diagnostic. The bones are easily fractured. In swine fed on potatoes, corn, etc., besides the affections of the limbs, the thickening of the bones and swelling of the joints, especially the hock and pastern, there is enlargement of the nasal and maxillary bones so as to seriously obstruct breathing (“Snuffles”). The teeth suffer and break readily and in the general break down diarrhœa, bronchitis or skin eruption appears and the subject falls into marasmus and perishes. In the necropsy arthritis is commonly found. In cattle beside the epiphyseal swellings, the bow legs and joint enlargements, the back becomes crooked, vertically or laterally. The same general symptoms appear in dogs in which bow legs are a very prominent feature. Goats suffer badly and mostly remain recumbent.
Birds suffer most, showing knotty thickening of the bones of the legs and wings, and flexibility of the bones generally but above all of the keel of the sternum, which is usually badly distorted from sitting on the perch.
In all alike there are usually a few days of fever, followed by indigestion, colics, anorexia, and a general air of illness. Then appear the lameness, stiffness and swelling of bones and joints. Any joint may suffer, shoulder, elbow, knee, hips, stifle, hock, or fetlock. The lameness may shift as in rheumatism, it may intermit, occurring periodically, or it may advance uninterruptedly to a fatal issue. Paraplegia is common and appears to be due at times to pressure on the spinal nerves by the diseased vertebræ. Before this becomes complete, the animal may walk with the whole digits and metatarsi in contact with the ground, and the softened crumbling calcis may project through the skin forming an unsightly sore which soon becomes septic. The same happens at times to the point of the elbow.
Treatment. The most important, are the hygienic considerations. Reject weak or cachectic animals from breeding, and those that have been rachitic to a marked degree, as their progeny are likely to show the same weakness. Change the ration giving one that is well balanced and rich in nutritive matters and earthy salts. Clover, alfalfa, and a generous grain diet may serve as an example for herbivora, and a fair allowance of meat and bones for dogs. Food from land that has apparently contributed to the disease in other cases is best avoided. If the land is poor, sandy, or destitute of earthy salts and phosphates, so much the more is it to be suspected and set aside. In the case of sucking animals it should be seen that the milk is rich and abundant, and that it is not too rich in fat, nor otherwise calculated to disagree and induce indigestion. Above all soured or otherwise fermented milk should be withheld, and any buckets or troughs used in feeding should be regularly washed, scalded and disinfected. In case colts, or dogs are being raised on cow’s milk it may be requisite to dilute it with one-third its volume of barley water, or solution of gum arabic, and to sweeten with sugar. Lime water with each meal is valuable in counteracting acidity, and fermentation, and in furnishing lime which may be absorbed in part.
In prevention and treatment alike, fresh air and sunshine must never be neglected and in warm weather, an outdoor life, night and day is of the greatest value. At the same time cold storms, damp beds, or any condition which may induce chill must be excluded. Close stalls, pens, or kennels must be absolutely forbidden.
Among medicinal agents antacids are often essential on account of the acid condition of the ingesta, lime water will often suffice, but if there is manifest constipation calcined magnesia three times a day on an empty stomach so as to counteract costiveness will often serve a good end. The atony of the bowel may be further met by small doses of strychnia. Other bitters may be used if this has little effect. Small doses of phosphate of soda, or bone dust have been long lauded in the affection, and probably act beneficially as a tonic as well as a food material. Phosphorus in minute doses tends to increase the deposit of earthy salts and consolidate the bones. Large doses induce hyperæmia of the epiphyseal ligament and even favor fracture. A grain of phosphorus daily may be given in olive oil or better in cod liver oil which acts as a valuable tonic. Dieckerhoff recommends the intratracheal injection of the solution of phosphorus in olive oil.