Part 15

Horse trading and the stabling of large numbers together is naturally the most fruitful of infection and hence strangles is a virtual plague in dealers’ studs. The buildings in such cases are reinfected at short intervals with virulent types of the streptococcus, and fresh susceptible animals are being constantly introduced to keep it up. Riquet says that in Northern Germany dealers avoid this largely by traveling their purchases in bands of 100 or 150 head, from ten to twelve miles a day, feeding sparingly, and turning them like sheep into an open park at night regardless of the weather. Much of the advantage is doubtless from the avoidance of stable infection and the warm relaxing air of indoors.

A sea voyage especially favors infection and a single victim placed on board will speedily contaminate all susceptible animals present.

Finally the predisposing influence of catarrh of the air-passages must not be overlooked. The inflamed mucosa furnishes a most inviting infection entrance.

Infecting products. The streptococcus abounds in the local phlegmons and abscesses, in the exudate of the submaxillary, pharyngeal or other glandular swellings, in the pustular eruption on the skin, and in the catarrhal discharge from the air passages. It further exists in the alimentary canal, in the ingesta and in the blood to a limited extent. In the bowels of an immunized animal it may remain virulent for months. Thus it comes that the manure is a source of infection, and that soiled fodder, litter and water may prove dangerous. The infected soil can not only harbor but can multiply the microbe, keeping it in readiness to attack any receptive horse. On his part the horse that is immune and in vigorous health may carry the infection for months and transmit it to his less resistant fellow.

While the streptococcus is usually found in the blood, in limited numbers only, its presence there implies its general diffusion and especially in the lymph plexuses and glands. Hence, the danger of operations on the subjects of strangles, the weakened tissues of the wound forming a most inviting field of growth. Castrations, occurring as they do mostly in the growing animal, are especially to be guarded against, and I may cite the case, familiar to many, in which seven cryptorchids died with phlegmon in the seat of the wound, the first one operated on having had strangles.

The nasal and buccal discharges are especially liable to convey the infection through mangers, racks, fodders, drinking troughs and pails, harness, poles and shafts, halters, twitches and the like. Infection through blankets, brushes, rubbers, and the clothes and hands of attendants, dealers, veterinarians and others, is not to be overlooked.

Pathology. The streptococcus shows a special disposition to enter and advance along the lines of the lymphatic circulation. The paucity of the germ in the blood and its abundance in the lymph plexuses, vessels and glands show that its election is preëminently for the lymphatic system. Then the ordinary primary lesions in and around the upper part of the air passage (nose, pharynx, submaxillary, parotidean and pharyngeal lymph glands) bespeak infection by inhalation, rather than with the ingesta. Primary solitary lesions on or near stomach or intestine are almost unknown; nearly all such being secondary. Next to inhalation, the most prominent channel of entrance is through castration and other wounds. Abrasions and sores of skin diseases must rank after wounds as entrance channels. Transmission by copulation the microbe being lodged on the genital mucosa is well established, also transmission from mother to fœtus through the placenta, and from dam to offspring through the milk.

In the most familiar type of the disease the nasal mucosa is red, congested and somewhat thickened with exudate, and the epithelium is softened and desquamating. As the result of this desquamation there may be slight abrasions or raw sores but these do not show indications of the irregular outline, excavations, or progressive extensions that characterize the ulcers of glanders. The surface is usually plentifully covered with a muco-purulent material with less disposition to adhesiveness than in glanders. It is rare to see any exudate into, and thickening of the walls of the lymphatics running from the nostrils toward the submaxillary glands. The predominance of the streptococcus in, and the entire absence of the glanders bacillus from the discharge and inflamed mucosa are conclusive. In the regular cases in which the submaxillary lymph glands are implicated, both right and left are usually involved, though not to the same degree, the exudate fills not only the gland tissue, but a large amount of the surrounding connective tissue as well, there is a great accumulation of lymphoid cells, and more or less extensive pus cavities, containing usually a white, creamy product. In the early stages the glands may be hard and nodular, as in glanders, but this condition is very transient, so that the rule is to find an extensive surrounding exudation filling up the whole intermaxillary space, and having a great abundance of small round cells with double or triple nuclei. In the older cases there is usually the open abscess, and if the case is an indolent one there may be extensive organization of the exudate with formation of dense, fibrous tissue. In some instances the nasal sinuses are filled with muco-pus.

When lesions extend farther implicating the pharynx and larynx, the mucosa of these parts shows the same redness, congestion, cloudy swelling and desquamation with, in some instances, small, submucous abscesses, and in others extensive infiltration of the submucosa with lymph so as to narrow or even close the lumen of the larynx. The guttural pouches may be filled with pus though this is far from constant. The pharyngeal lymph glands, are nearly always involved and often the lymph gland in the parotid so that a general infiltration of the surrounding parts is met with.

If the chest is implicated there is congestion of the bronchial mucosa, engorgement of the smaller bronchia, air sacs and cells with pus, collapse, carnification or congestion of lobules, in some cases pulmonary abscess, and, finally, swelling and not infrequently abscess of the bronchial glands. Pleurisy is a not uncommon accompaniment, appearing it may be as a simple extension, from the lung, or, in the worst forms, from rupture of mediastinal or glandular abscesses into the cavity and severe infection of the entire pleural walls. The pericardium is exceptionally involved and coagula on the tricuspid valves have been met with (Zschokke).

Circumscribed phlegmonous exudates and small abscesses are sometimes found in the mouth (tongue, soft palate, cheeks) and less frequently in the œsophagus.

The stomach may show congestions, petechiæ, circumscribed hæmorrhages, ulcers, and abscesses of the gland tissue or submucosa. Rupture of the walls may follow abscess (Cadeac).

The intestines may show congestions, colorless or hæmorrhagic exudate, and suppurations in the agminated or solitary glands, or submucosa. The intestinal, mesenteric and sublumbar lymph glands may be the centres of abscesses of varying sizes.

Abscesses may also be found in the liver, pancreas, spleen, of variable size and usually as secondary formations.

The muscles and intermuscular tissue may be the seat of more or less extensive exudation, and abscess, and the bones may be congested and swollen especially in their epiphysis. This may extend to suppuration or necrosis.

The synovial membranes of joints and the tendinous sheaths are not infrequently inflamed causing distension and even suppuration.

Congestions of the skin are sometimes met with developing as multiple papules or hard nodules which advance to the formation of pustules or small abscesses. These often appear especially where the skin is thin and delicate as around the lips, nose and eyes, close to the anus or vulva, in the perineum, sheath or mammæ, inside the thighs or elbow. They may be of all dimensions from a millet seed upward, and may merge into or become complicated by the extensive engorgements of petechial fever.

Finally lesions of the nerve centres are to be looked for in the protracted or irregular types of the disease. There may be simple congestion, or serous effusion, intraventricular or subarachnoid, or finally abscess in the brain, spinal cord or meninges.

Forms of Strangles. The types of strangles vary, special forms characterizing given epizoötics or seasons, or at other times as individual deviations from the current type. Division has been made into two groups—mild and malignant, or again into regular and irregular, under each of which come several varieties. Many of these varieties consist simply in a difference in the seat of the principle lesions, which start in lymph glands or tissues at a distance from the nasal mucosa, or they depend on secondary foci of infection supervening on the primary disease in the head.

Incubation. In inoculated cases this lasts from three to five days, in those due to simple exposure it may appear to extend over eight days.

General Symptoms. In nearly all cases alike there is a marked constitutional disturbance the temperature often rising at once to 104° to 106° F., and oscillating on successive days between this and 102°; the pulse is usually normal at first and the breathing is either slightly accelerated or may be made so under slight exertion. There is more or less dulness, or at least a lack of the vivacity of youth, the head is somewhat pendent, the eyes may be semiclosed, the patient may be tardy or even stiff in his movements and the appetite may be diminished or capricious, oats being rejected by some and hay or grass by others. The bowels are somewhat confined, the stools consisting of a few small, hard, balls covered with mucus.

Specific Symptoms in the Mild Form. In the vast majority of cases the local symptoms are concentrated on the mucosæ of nose and mouth, and the submaxillary lymph glands. Along with the general febrile phenomena, there appear redness and often mottled congestion of the nasal mucosa, which not infrequently extends to the mouth and eyes, as well. Heat of the mouth, the collection of a more or less tenacious mucus, and even uneasy movements of the jaw may be seen. The nasal mucosa, at first dry, is soon the seat of a watery exudation, passing into a cloudy sticky material, and finally a thick, opaque, muco-purulent flow. This may become colored of a variety of tints, dirty white from inhaled dust, brownish or yellowish from exuded blood, or greenish from food materials. The discharge is usually profuse in the young and may be scanty in the old. Most commonly it flows from both nostrils alike, though exceptionally it is unilateral. In this it differs from glanders which is more often unilateral though at times bilateral. Small abrasions and sores may appear in connection with the softening and shedding of the epithelium, but these are not ragged, irregular and spreading as in glanders. Sneezing or snorting is an inevitable symptom. Epiphora is usually present. Exudations into the nasal sinuses are to be recognized by heat of the forehead and flat sound on percussion.

Very early in the attack a swelling is noticed in the intermaxillary space, which may be at first confined to the nodules of the lymph glands, thus forming distinct, rounded, hard swellings, but they are early covered by a diffuse exudation into the surrounding connective tissue, that completely envelopes and obscures the form of the swollen glands, and forms a more or less uniformly rounded, pasty swelling, extending to the median line of the intermaxillary space, or filling the whole space from one maxilla to the other and projecting downward below their level. This early, diffuse, pasty, evenly rounded swelling, hot and tender, is distinctive of strangles, and usually exclusive of glanders.

Another characteristic of the strangles swelling is its steady, and usually speedy, advance to suppuration and abscess. It becomes hard, tense, and resistant, then, in the centre, or at various points of the surface, small areas of circumscribed softening can be detected, and soon show distinct fluctuation. Two or more of these may coalesce or they may form several distinct abscesses, which may early point, burst and discharge, when the remainder of the exudate softens and degenerates into pus, and the cavity closes by granulation. In some cases after the formation of the swelling it disappears by resolution, the exudate becoming liquefied and absorbed. In glanders the nodular, insensible, swelling tends to persist without extensive pasty exudation or suppuration.

Cases of strangles catarrh in which the submaxillary lesions are omitted, are quite common. These occur during the regular strangles epizoötic, and protect against a second attack.

Symptoms of Pharyngeal and Laryngeal Strangles. Extension of the morbid process from nose to pharynx is exceedingly common. When concentrated on the pharynx there are extension of the head forward with elevation of the nose, swelling of the throat laterally or downward, uneasy movements of the jaws, salivation, difficulty of swallowing, return of ingested liquids through the nose, gulping, and a loose suffocative cough. The swelling of the throat tends to attain to large dimensions, and may threaten suffocation by interfering with the breathing. This is still further aggravated if the laryngeal mucosa is the seat of exudate. The breathing may become loud and stertorous, the mucosæ of a dark leaden hue and the animal dull and stupid from the venous condition of the circulating blood.

Abscesses forming on the lateral parts of the throat usually make their way to the surface though this may be below the level of the parotid. If from the parotidean lymph gland, one of the ducts may be opened thus forming a salivary fistula. If from the retro- (supra-) pharyngeal glands the rupture into the pharynx is more likely to take place, but in some cases the investing sac, meeting with equal resistance in all directions, fails to undergo degeneration and softening at any one particular point, and the contents remain pent up indefinitely. If the liquid is absorbed a cheesy or putty like mass may be the final outcome, with chronic cough, some stertor in breathing and it may be difficulty in swallowing.

If the guttural pouches should be involved, there is deafness, parotidean swelling, which may eventuate in a fluctuating swelling at the lower border of the parotid, and a free discharge when the head is lowered, which is likely to last after general recovery. (See Guttural Pouches, pus in).