No. 6. DEPARTMENT OF AGRICULTURE. 135 



Epizootic lymphangitis is 'caused by a special yeast like fungus fSaccliaromyces 

 farciminitxiisj that is capable of growing in the tissues of the horse and mule. 

 This parasitic plant occurs as minute cells, of characteristic form, in the pus 

 that is disharged from the abscesses and the ulcers that it produces. Such in- 

 fectious pus, or the disease producing organism that it contains, when brought 

 in contact with an abrasion of the skin of a healthy hoise may enter the abra- 

 sion and cause a local focus of disease. The infectious material may be trans- 

 ported by contact between the diseased and healthy horses, by stall bedding, by 

 stable utensils, by harness, and in a variety of other ways— quite possibly by 

 flies. 



The important points are that the disease never occurs excepting as it is 

 caused by this particular parasitic plant, and this plant is distributed only by 

 horses or mules affected with this disease or by material contaminated with 

 the discharges from such animals. 



After entering a wound, or an abrasion of the skin, the organism grows, at 

 first very slowly, and causes a local inflammation followed by the formation, 

 in from three weeks to three or more months, of a nodule (a small, rather 

 spherical, dense, tumor-like mass) beneath the skin and by th« hardening and 

 thickening of the regional lymphatic ducts and glands. The nodule gradually 

 softens and forms an abscess, which discharges pus, leaving an indolent ulcer. 

 Such processes occur most frequently upon one or both hind legs, but may occur 

 in any part of the body and are not infrequently seen on a front leg, or on the 

 shoulder or the side of the neck. The infection is carried by the lymphatic 

 channels or it is spread over the surface and enters some abrasion on another 

 part of the body. In these ways, the disease may spread in the individual sub- 

 ject. 



A few horses appear to recover spontaneously, some may be cured by appro- 

 priate treatment, if treatment is started during' the early stages, before much 

 tissue is involved and while the lesions are superficial and may be got at; many 

 subjects are not curable and continue to discharge and scatter infectious ma- 

 terial, a menace to other horses, as long as they live. 



,' The disease is said to be fatal in from 10 to 15 per cent, of all cases. Many 

 cases that do not terminate fatally are very prolonged, extending over years, 

 and these may result in the thickening of the legs to such an extent as to in- 

 capacitate and ruin a horse, though he may not be killed by the disease. 



The importance of epizootic Ij^mphangitis must be considered from the stand- 

 point of the individual horse owner and from that of the public. 



To the owner of a single infected horse, the matter may, or may not, be of 

 serious pecuniary importance. If the case is a light one and if it follows the 

 usual slow course, the infected horse may render service of but little less than 

 normal value for months; in some cases for years. On the other hand, the dis- 

 ease may follow a more rapid course and cause numerous nodules, abscesses 

 and ulcers on various parts of the body and a thick leg or two, and destroy 

 from 25 per cent, to 75 per cent, of the market value of the horse, even if it is 

 not rendered entirely unserviceable. 



To horse owners at large — to the public — this disease is important, because, 

 if it is not controlled, it will make another addition to the list of destructive 

 diseases that are continuing- sources of loss, and that must be guarded against. 



The most common manifestation consists in the presence of small, chronic, 

 discharging ulcers in the vicinity of the hook joint of a thickened hind leg-. In 

 such a case, one may also find small scars showing where ulcers have healed 

 and there will probably be some finr. nodules beneath the skin and, perhaps, 

 one or more nodules that have softened, forming- fluctuating- abscesses. The 

 regional lymphatic ducts are corded and the glands inside the thigh are hardened 

 and nodulated. 



The earliest observed symptom may be the occurrence of a firm nodule, from 

 the size of a pea to that of a walnut, beneath the skin, anywhere on the body. 

 Corded lymphatics extend from this lesion. In time, the nodule will soften and, 

 at length, its purulent contents will break through the skin. The time required 

 for these developments is most variable and may reach several weeks. Such 

 pus is thick yellowish or greyish yellow and often it is mixed with blood. 

 Sometimes it contains flakes. 



In other cases, the first symptom observed is an indolent sore, covered with 

 pus and scab, surrounded by a slightly swollen zone and from which one or 

 more firm cords extend beneath the skin to-w^ard the lymphatic glands. This 

 condition is, no doubt, the first to develop, but such a sore often escapes special 

 notice until nodules occur. 



Fresh ulcers may he surrounded by a slightly raised zone of bright red gran- 

 ulation tissue ("proud flesh"). The ulcers occur irregularly and they disappear 

 slowly; some heal in a fortnight, others continue to discharge for months and, 

 after healing, may break out again. From this long continued irritation and 

 from the formation of scar tissue, the skin thickens and the affected parts 

 become indurated. 



Ulceration sometimes occurs upon the conjunctiva and on the mucous mem- 

 brane of the nostrils and upper respiratory tract. 



The affected horses do not, as a rule, show any constitutional disturbance ex- 

 cepting in very advanced cases. 



