Definition. An infective, ulcerative inflammation of the large intestine but especially of the colic and rectal mucosæ.
It is well recognized as a disease of the ox, and the older writers allege its existence also in horses, swine and dogs, though this is not admitted in all modern veterinary works.
Causes. It was formerly ascribed to improper hygiene, chills, cold rain storms, night dews, hoar frost, malarious emanations, putrid, stagnant or iced water, irritants in food, green, fermented or musty food, a too liberal diet after starvation, overtaxation in very hot weather, and bad odors from decomposing carcasses. These can only be accepted as predisposing causes begetting a general debility, or debility of the alimentary canal and laying that open to the attacks of specific microbes. The close aggregation of cattle on ship-board, in besieged cities, and in the parks of armies in the field, has apparently contributed to the propagation of the dysentery. The removal of a victim to a herd with free healthy range seldom starts a new center of the disease. In all infected herds huddled in small compass there is every facility for the propagation of a germ already present, and especially in the commissariat of a belligerent army there are enough privations, over-exertions and other trying conditions to favor predisposition. Faulty food like stale bread, musty hay, have been supposed to cause it. For man and beast alike dysentery is preëminently a disease of the tropics, and of hot seasons, and will often subside on the advent of cold weather.
Its propagation on given (swampy) soils, and in particular (foul) stables strongly suggests a special germ, though for the cow this has not been perfectly identified. Gerlach vainly attempted to inoculate it, and it does not often propagate itself beyond the foul and infected localities or stables, yet its persistence in them for years bespeaks unequivocally the operation of a special pathogenic ferment.
It may also be fairly assumed that it is not necessary that the same factor should be present in all cases alike, but that one operates predominantly in one case and another in another. In other words dysentery must be recognized as not one disease, but several, of which the true pathogenic microbes have not yet been fully demonstrated, but which are classed together because of the similarity of the attendant lesions.
In man three distinct forms are recognized. 1. Catarrhal dysentery, with frequent small stools of rosy mucus, and blood; and later pus, scybala, passed with tenesmus, but no sloughs and little odor; 2. Diphtheritic dysentery, with thin watery bloody discharges having a pronounced cadaveric odor; also tenesmus, sloughs, and increasingly offensive smell; 3. Amœbic dysentery with frequent bloody mucus stools, tenesmus sloughs and fœtor, but with distinct remissions or intermissions. With the latter, amœbæ are found abundantly and more so in the more acute cases with alkaline stools. They are found in the fresh warm stools, 5 to 8 times the size of a red blood globule and oval, pyriform or irregular in form, with nucleus and nucleolus. Kartulis and Hlava succeeded in inducing dysentery in cats and dogs by injecting pure culture of the amœba, and the former testifies that dogs in Egypt take the disease spontaneously, and their stools contain the same amœba coli as is found in man.
Cunningham who investigated the subject in India found amœba in the bowels of healthy men, and also abundantly in the fæces of horses and cows, which have naturally the requisite alkaline reaction.
The mere presence of the amœba therefore may not be sufficient to cause the disease, but with the requisite predisposition and an alkaline condition of the intestinal contents, it is manifestly an important factor in the disease.
The causative microbes in other forms of dysentery have not been identified, but under the requisite irritation and local debility one can easily conceive of the ordinary bacterial ferments of the intestine, concurring with others introduced from without, in determining the morbid condition. With better hygiene the disease is steadily diminishing in man and beast, though violent epizootics (in cattle) still appear in connection with wars (siege of Belfort, 1870, Zundel), and carriage by sea in hot climates (Mediterranean trade, Bouley).
Symptoms. The disease sets in suddenly, yet prodromata may occasionally be observed, such as dullness, langor, trembling over the flanks and elbows, weakness, prominent, weeping, congested eyes, and low moans when moved. Then follow hyperthermia, at first slight, heat of the mouth without injection, epithelial concretions or erosions and diarrhœa (sometimes there is straining without passage at first). Then follows a period of profuse and fœtid discharge, with relaxed or open anus, the liquids escaping involuntarily and smearing the tail, perineum, thighs and hocks, and the protruded mucosa showing dark red congestions and even commencing erosions. Colicy pains, slight at first, have now become intense, and the right side of the abdomen is very tender to the touch and fluctuates noisily when manipulated. Appetite and rumination are lost. Salivation may be present, the saliva falling in films to the ground. The buccal epithelium is softened, loosened and easily detached by the finger, leaving raw sores. The temperature which has risen slowly (not as in rinderpest abruptly) may reach 106°. The hair becomes dry, the skin harsh, rigid, and firmly adherent to the deeper parts, and often cold, while the muzzle is hot, dry and even cracked.