Laminitis consists of an inflamed condition of the sensitive laminae, or, more properly, of the entire thickness of the layer of skin which intervenes between the hoof and the pedal or foot bone. In addition, however, to this, the foot bone itself is invariably in a state of general congestion, and in acute and protracted cases undergoes very marked changes of form and structure in consequence. The disease is much more prevalent in the heavier than in the lighter breeds of horses, and among stallions especially during the early period of the season when their services are first called for.
By some heredity is regarded as a predisposing factor in the production of the disease, and there is much to be said in favour of this view of its origin. Animals with wide, flat feet, low at the heels, and wanting in hoof-horn, are especially liable to contract it, but none can be said to be altogether exempt from it. The exciting causes are many and various. Among them may be mentioned high feeding during a long period of idleness, the injudicious use of certain kinds of grain, especially barley, beans, and wheat when new. It is also provoked by long and fast driving on hard roads, particularly in horses with high beating action and heavily fleshed.
It frequently follows upon protracted disease of the organs of the chest, which compels the sufferer to stand for long periods without removing the weight from the feet; and, for reasons which cannot be clearly stated, it sometimes comes on after foaling, and less frequently in consequence of the action of a dose of physic. It may also result from exposure to cold and wet after a long and fatiguing journey.
The onset of laminitis is usually sudden, and little or no warning is given of its oncoming. The fore-limbs are most frequently affected, but sometimes the hind ones are also implicated at the same time. In this disease the posture and gait are very diagnostic. The animal stands in a crouching position, with the fore-feet extended far in advance of him, and the hind-legs are brought forward under the body to sustain the weight of which the fore ones have been relieved. When made to move, the action is short, jerky, and painful, and the weight of the body is thrown on the heels.
Posture in Laminitis of the Fore-feet.
Laminitis in Fore- and Hind-feet.
PLATE XLIV. LAMINITIS.
The feet are hot to the touch at first, and may later become quite cool. If struck with a hammer, however lightly, pain is induced. In severe attacks the suffering is very intense, and constitutional disturbance is evinced by an anxious expression of the face, hurried breathing, a quick hard pulse, heightened temperature, restlessness, and patchy sweats. The mucous membranes of the nose and eyes are of a deep-red hue, the mouth is hot and clammy, and the bowels are constipated. In cases where the hind-feet are also affected it is difficult to induce the animal to move, and he stands fixed to one spot, or falls to the ground, where he remains unable to rise.
Unless relief is speedily afforded, the feet undergo marked changes of a permanent character. The soles "drop", owing to the coffin-bones having become separated from the hoof and displaced, and the front of the foot sinks in, so that while the one becomes convex or unduly prominent, the other becomes concave or depressed (fig. 395). Later, rings appear on the hoof owing to irregularity in the secretion of horn, and the texture of the latter becomes loose and shelly (fig. 396). The toes increase in thickness and become rounded, and have a tendency to turn upward.
In all cases of this affection the bowels should be unloaded as speedily as possible by a full dose of physic, and if the patient is seen at the outset, blood should be taken from the jugular vein, particularly in the case of plethoric animals. To relieve the feet of the weight of the body and mitigate suffering, the patient may be put into slings and kept there as long as he is able to endure the position. Should he become restless, he may be liberated and allowed to lie down, where he should be encouraged to remain. In either case a good bed is to be provided, comprising a foundation of peat-moss, with a fair covering of straw. The latter will be required to pack the body and protect the head from injury when struggling on the ground.
Fig. 395. - Laminitis.
1, Coronary cushion. 2, Healthy horn. 3, Cicatricial horn. 4, Os pedis displaced by pressure. 5, Heel displaced by pressure.
Fig. 396. - Laminitis.
When practicable, the shoes should be removed without delay, and the feet placed in hot bran poultices, which will require to be renewed frequently, and in no case allowed to become cool. If the pain is very severe and the constitutional disturbance runs high, a full dose of morphia may be injected beneath the skin, and repeated once or oftener according to the requirements of the case.
When substantial relief has been afforded and the inflammatory symptoms subside, poulticing may be discontinued, and the feet freely and repeatedly irrigated with cold water, and as soon as possible the patient may be made to move about the box. If a pond is accessible, he should be led into it and allowed to remain with the affected feet in water for several hours at a time, or, failing this, a deep layer of wet clay may be laid in the stall, where he should be made to stand. Gentle walking exercise on a soft surface of tan or manure should be enforced for short periods two or three times a day, and finally a sharp blister should be applied to the legs, from the coronets as high as the middle of the canon, and repeated once or more at suitable intervals if required. When the soreness has passed away from the blistered surface the patient may be turned into a soft meadow, by preference one adjoining a river. If shoes are applied to the feet, they should be short and moderately thin at the heels, so as to admit of the weight being thrown on to the posterior part of the foot.
Death from laminitis is by no means rare in severe attacks of the disease, and structural changes with or without deformity of the feet almost invariably result in a greater or less degree.