Horses do not suffer from distension of veins as does man, that is, there is rarely to be seen a case wherein much disturbance from this source exists.
Inflamed lymph vessels and glands, the result of various causes, is a rather common source of lameness of horses. When one considers the proportion of tissue that is composed of lymph vessels and glands, it is then obvious that inflammation of these structures should cause a painful affection of members, when so affected, and that marked lameness and, in some instances, general constitutional disturbance such as anorexia, hyperthermia and general circulatory disorder are to follow.
Lymphangitis is most frequently occasioned by the introduction of septic material into the tissues; consequently, infectious lymphangitis is more frequently observed than the non-infectious type.
Specific infectious forms of lymphangitis are seen in glanders and in strangles; infectious types of this disturbance are found in many instances where, initially, a localized or circumscribed infection has occurred—the contagium having been introduced by way of an injury. An example of this kind is to be seen in a wound perforating the tibial fascia, where the injury is inflicted by means of a horse being kicked by another animal shod with sharp shoe-calks. Cases of this kind invariably result in a septic lymphangitis, and frequently lymphadenitis also occurs, for the inguinal lymph glands are so situated that their becoming contaminated is almost certain.
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 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.