Lameness of the Horse / Veterinary Practitioners' Series, No. 1

by John Victor Lacroix

The trite phrase that "the tissues are bathed in lymph" should make clear the reason for the frequent occurrence of infectious lymphangitis and lymphadenitis. Foreign substances, bacteria and their products, inorganic material and in fact, anything that is introduced into the tissues, if soluble or miscible, will be taken up and conveyed by the afferent lymph vessels and disseminated throughout the system—hence the constitutional disturbances so frequently thus caused.

A non-infectious type of lymphangitis is frequently seen in the heavy draft breeds of horses and in such cases one or both hind legs are involved—it is very seldom that the thoracic limbs become so affected. Law[3] refers to this ailment as "Acute Lymphangitis of Plethora in Horse." When one takes into consideration that these cases so frequently occur in heavy draft animals that are not worked regularly, that the pelvic limbs are the ones involved, and that the disorder often runs a short course (recovery often taking place within two or three days, with no treatment given other than a purge, circulatory stimulants and walking exercise) it is plausible to ascribe the condition to idiopathic factors.

Admitting the frequency of non-infectious lymphangitis, the practitioner must not confuse this type with similar lymphatic inflammation occasioned by nail punctures of the foot. It is very embarrassing indeed to make a diagnosis of lymphangitis—expecting that the disturbance will terminate favorably and uneventually—and later to discover a sub-solar abscess caused by a nail prick in the region of the heel.

Recurrent attacks of this disturbance cause hypertrophy of the lymph vessels and in some cases lymphangiectasis. In old subjects used for dissection or surgical purposes, it is very evident that in the ones which have suffered from chronic lymphangitis there exists an excessive amount of sub-facial connective tissue, making subcutaneous neurectomies quite difficult in some instances.

A sequel of chronic lymphangitis is a condition known as elephantiasis. In such cases there occurs a hyperplasia of the skin and subcutaneous tissues, resulting in some instances, in the affected member attaining an enormous size. Sporadic cases of this kind are to be seen occasionally, and are apparently caused by repeated attacks of lymphangitis. The affection is not benefited by treatment, and while a horse's leg may become so heavy and cumbersome as to mechanically impede its gait, as well as to fatigue the subject when made to do service even at a slow pace, elephantiasis causes no constitutional derangement. The hind legs, in elephantiasis, are affected and a unilateral involvement is more often seen than a bilateral one. The legs may be enlarged from the extremity to the body, but ordinarily the affection does not extend higher than the hock or the mid-tibial region.

A chronic, progressive, hyperplastic-degeneration exists in some cases and the subjects are in time rendered unserviceable because of the burden of getting about encumbered by the affected extremity. In other animals hyperplasia progresses for a time—until the parts become greatly enlarged and conditions apparently attain an immutable state. Nevertheless animals so affected may continue in service for years without being distressed.

AFFECTIONS OF THE FEET.

Lameness is very often due to affections of the feet, and in all foot diseases probably the most constant cause is injury inflicted in some manner. Resultant from injury, there frequently develops complications and the one most often seen is infection.

Because of the fact that the feet are constantly exposed to germ-laden soil and filth, if not actually bathed in such infectious materials, it naturally follows that septic infection of some part of the feet must be of frequent occurrence.

Subsequent to being obliged to stand in mud and other damp or wet media, exposure to desiccating influences such as stabling upon dry floors, or at service on hot and dry road surfaces causes the insensitive parts of the feet to become dry, hard and brittle. This favors "checking" of the protecting structures and it frequently results in the formation of large fissures which expose the underlying sensitive parts of the feet and lameness is the inevitable outcome.