Various forms of abnormal metabolism are invoked as the cause of uric acid and gout, and Haig and Vaughan hazard the theory that the breaking down of the nuclein is an important factor. This and other metabolisms are attributed to the local action of the uric acid and urates, and again to a fault in innervation. The imperfect action of the liver where the uric acid should be largely resolved into the more soluble urea, and of the kidneys through which it should be promptly excreted must be attributed to a nervous source. Levison incriminates the granular, contracted, inactive kidneys.
Ebstein attaches great importance to impaired nutrition in the affected tissues which undergo necrotic changes that pave the way for the deposition of urates in their substance. This is somewhat sustained by the occurrence of the local deposits in tissues in which circulation and nutritive changes are slow, and in older animals in which not only are the osseous tissues more calcic and less vascular, but the articular lamella has been formed by cretefaction of the bone and cartilage. Haig suggests that in the old, the joints are less vascular and less alkaline, and more sensitive to cold. On the other hand those in the greatest vigor of life are more ravenous, digest more actively and are in this sense more subject to injury from excess of uric acid and allied products. Birds at this age, confined and in process of fattening are thereby exposed. Overfed, obese, lazy, old house dogs are under similar causative conditions.
Lesions. The most prominent lesions in birds are chalky concretions of urates on the articular ends of the bones and in the structures around the joints including even the tendons, with more or less inflammatory exudate and even necrosis, invading the bony tissue and articular cartilage. Abscesses may be present usually outside the bursa. Birds suffer especially in the tarsal, metatarsal and phlangeal joints, but often also in the corresponding joints of the wing, and less frequently in the joints of the trunk, and in the internal organs,—kidneys, liver, lungs, serosæ,—and skin. In these last, miliary chalky concretions and encrustations are found. In Brückmüller’s case in the dog the chalky deposits of urates were found mainly on the epiphyses of the ribs, but also on the joints of the limbs.
Uric acid is always abundant in the blood of birds, and Roberts has shown that biurate of soda (the usual form of precipitate) is insoluble in blood serum, synovia and other body fluids when in excess of 1:10,000.
Symptoms. In birds the febrile and constitutional symptoms have not been carefully observed so that the objective symptoms in the affected joints have been mainly relied on. There is extreme tenderness marked by standing on one limb, or resting on the breast, and hence moping apart from the flock. When made to rise, the affected limb may be used to steady the body, or even to walk, with a limp, though in bad cases the sound limb only may be used. The affected joints are swollen, soft, hot, extremely tender, pitting on pressure, and later the seat of nodular yellow masses, usually hard, but sometimes fluctuating and in size from a pea to a hazel nut. The superimposed epidermis is thick, dry and scaly, falling off in flakes. At a more advanced stage the concretions may burst through the skin, discharging a buffy, granular, debris containing crystals of urates of ammonium or calcium, or of uric acid. Later still are ulcerous sores, involving the disintegrating urate nodules and the necrotic bones and cartilages. The deposits deflect the bones from their normal direction, causing not only nodular swellings on the toes but much crookedness and distortion. As in man the disease is essentially chronic and advances slowly, with anæmia, emaciation, debility and at times diarrhœa.
Diagnosis depends largely on the recognition of the excess of urates in the deposits. These appear under the microscope as fine acicular crystals, which in the harder portions have a concentric arrangement. A portion of the concretion may be moistened with a few drops of nitric acid and evaporated to dryness. To one part of the residue is added, by means of a pipette, a drop of aqua ammonia, and to another caustic soda. The ammonia develops a beautiful purple red color, and the soda a blue or purplish blue ring (Murexide test). In tubercular joints, which are common in birds, the caseated nodule is made up of cells and granular debris, with tubercle bacilli, and though cretaceous particles may be present they fail to give the microscopic and color appearances of uric acid.
Treatment. This must be largely preventive. The rich albuminoid feeding and close confinement must be modified especially in the older birds, and eliminating agents must be given in the drinking water. The Carlsbad combination (sodium sulphate 22; potassium sulphate 1; sodium chloride 9; sodium bicarbonate 18) may be used. Powdered colchicum ¼ gr. once or twice daily during an attack, or piperazin ½ gr. twice a day. Locally, abscesses should be opened, and like any sores or ulcers, treated with antiseptics (Salicylate of sodium 75 grs., glycerine 2 ozs.; or piperazin solution 2:100).
SCURVY: SCORBUTUS.
Definition. Susceptible animals: pigs, dogs. Causes: unwholesome salt meat, lack of fresh food, vegetables, potassium, bad environment, unvarying diet, lack of free range, putrescent food, foul water, infection; non-recurrence. Lesions: blood black, diffluent, little rigor mortis, excess of sodium, petechiæ and extravasations, red marrow, softened, swollen, bleeding, ulcerating gums. Symptoms: Anorexia, prostration, debility, tardy movements, petechiæ, loss of bristles, ulcers, gum lesions, joint swellings, blood extravasations. Diarrhœa. Prognosis unfavorable. Treatment: correct unwholesome environment and food, wash, rich food partly green or animal, iron, bitters, arsenic, mouth wash (potassium chlorate), for suckling milk. Butcher.
Definition. Scurvy is a subacute or chronic trophic disorder characterized by debility, inanition, anæmia, swelling and bleeding of the gums, gingival ulceration, dropping of the teeth, and petechial or more extensive hæmorrhages and exudations in the skin, serosa, and solid tissues.