In localized external anthrax the local swellings may be first seen. There are usually some tenderness of the skin, erection of the hair, and the formation of a little nodule, like a hazel-nut or walnut, adherent to the deeper parts of the skin, firm and comparatively painless even when cut. Sometimes the swelling is diffuse, with a dropsical or erysipelatoid aspect, and crackles like parchment when handled. Whether the affection attacks the tongue, the throat, or some part of the head, body, or limbs, the tendency is to gangrene of the part, and, if the subject survives long enough, to an extensive sloughing and unhealthy sore. The sloughs and sores have either a black sanguineous appearance or they are lardaceous and intermixed with streaks of dark red. If fever is not present at the outset, it sets in early, and passes through the same stages as in the acute internal anthrax, the animals being suddenly plunged in prostration and stupor, with dusky yellow or blood-stained mucous membranes, dyspnoea, dilated pupils, convulsions, and death. On the mucous membranes (gloss-anthrax, anthrax angina) the engorgement is usually complicated with bullæ with red or yellow contents, and which on bursting leave unsightly gangrenous ulcers. In all such cases the morbid liquids of the swellings teem with bacilli.
MORBID ANATOMY.—The most characteristic changes are usually met with in the blood. This is black, thick, tarry, uncoagulable or coagulates only in loose diffluent clots, which are redissolved before squeezing out the serum; the fibrin is diminished (often by two-thirds), the red globules are not adherent in rouleaux, and are crenated and broken down and the hæmatin diffused through the liquid, so that it stains the hands or paper deeply; the white globules are increased, probably by reason of the early irritation of the lymphatic glands and spleen by the poison; and it reddens slowly and but slightly on exposure to the air, and speedily passes into decomposition. The blood can scarcely be made to flow in a full stream, but often trickles down the hair and skin by reason of its thick, consistent character. The microphytes above described are usually found in the blood, and always in the affected tissues if examined just after death.
Next to the blood, the spleen presents the most constant lesions, being enlarged (by one-third, one-half, or to double, triple or quadruple its normal size) and gorged with blood (sometimes even to rupture). The lymphatic glands, and especially those adjoining the local anthrax swellings of the tissues, are always enlarged, marked with petechiæ, friable, easily reduced to a pulp, and swarming with bacilli and micrococci. Next to the glands of the affected parts the central ones, the axillary, prepectoral, thoracic, sublumbar, and abdominal, are the most constantly affected. The lymph is reddish and opaque.
Decomposition sets in early, and the resulting gases cause a puffy, emphysematous condition of the connective tissue. The fat and other white tissues are dusky brown or yellow, and petechiated; the muscles are soft, flabby, and dark red or brown, with occasional blood extravasations; the blood-vessels, especially the veins, and the right heart are gorged with black, uncoagulable blood, and have their inner coats blood-stained. The serous membranes present numerous petechiæ, and contain more or less of a reddish serum. The intestines, and sometimes the stomach, are dark red throughout, marked by petechiæ, and are often the seat of thickening from sanguineous or transparent colloid infiltration. The lesions are especially extensive on the small intestines and rectum. The vagina and womb are also the frequent seats of sanguineous infiltration. The liver and kidneys are enlarged, congested, softened, and friable, and the ganglia of the sympathetic are enlarged, congested, and softened. The swellings are of two kinds, sanguineous and colloid. The former, when cut into, present one or more loose clots of black blood or a grumous mass of blood-elements, separating the tissues and often mixed with fetid gases. The colloid exudations are glairy, semi-solid, jelly-like masses, infiltrating the tissues. The tissues affected and the skin covering them are the seat of bacterial embolism and gangrene, and there is no tendency to suppuration. These products swarm with the specific microphytæ.
DIAGNOSIS.—The differential diagnosis of anthrax from other affections due to the propagation of microzymes in the system is not always easy—so much so that a variety of bacteridian and allied diseases (septicæmia in its various forms, erysipelas, swine plague, chicken cholera, poisoning by the micrococci of fungi, black quarter from bacteria, milk sickness, and Texas fever) have been erroneously confounded with this affection. These all show the same dusky or cyanosed mucous membranes, disintegrating blood-globules, loose blood-clots, petechiæ, blood-extravasations, sudden and great prostration, and enlargement and congestion of the lymphatic glands or spleen. In some of these the duration of incubation (in swine plague six to fourteen days and in Texas fever one month) serves to distinguish, while in the majority the microzyme is globular (Texas fever, micrococcus of fungi-poisoning, chicken cholera); in swine plague the cocci are arranged in pairs; in black quarter the microbe is a refrangent ovoid, single or in chains of two or three and a motile linear body with a refrangent nucleus in one end; and in milk sickness the germ is a spirillum. The germs are far more likely to be detected in the local lesions and lymphatic glands than in the blood. The specific nature of the symptoms and lesions can usually be relied on, but in cases of doubt the inoculation of a small animal (rabbit, guinea-pig, sheep) will be a material guide.
PROGNOSIS.—True anthrax leads to a very high mortality. The apoplectiform cases are fatal almost without exception; the acute cases of anthrax fever in many outbreaks perish to the extent of 75 or 80 per cent., and the more tardy ones to the number of 50 per cent. In a general outbreak the earlier cases are usually the most fatal, while later, when the less susceptible animals are attacked, the mortality is often decreased. Again, the mortality is often at once arrested by the emigration of the herd to a more healthy soil, a large proportion of those already attacked recovering.
PROPHYLAXIS.—In prophylaxis the soil demands the first attention. If this is damp and calcareous or rich in organic matter, the remainder of the herd should be at once removed to a drier and more porous soil, where the germ is less likely to be preserved and increased. In an enzoötic in Livingston County, N.Y., in 1875, 40 bullocks out of 200 had perished in ten days, yet after removal to an adjacent dry pasture and the use of antiseptics with the food and water the attacks abruptly ceased and 48 out of 50 head already sick recovered. The drainage of anthrax soils leads to a steady reduction of the poison, favoring as it does the germination of the spores and the destruction or modification of the germ. When drainage is impossible, the mortality may be reduced by driving the stock to drier grounds during the hot, dry season, by stabling them morning and night when the dews are on the grass, also in wet times, when they are likely to pull up the plants by the roots, or, better still, by cutting the fodder and soiling the stock in stables or yards. Yet in all these cases the germs will at intervals find access to the animals in the green food or hay, so that badly infected soils must be secluded from live-stock, and either be abandoned or devoted to other cultures. A point of the very first importance is the safe disposal of the products and carcases of the sick. These should be thoroughly burned, or, failing this, deeply buried (4 feet) and the graves covered with coal tar and fenced in from all other stock for from five to ten years. Contaminated litter and fodder should share the same fate. Stables and yards where the sick have been, and all vehicles and implements used for them or their products, should be thoroughly disinfected. In the epizoötic in Livingston County, above referred to, these measures seem to have eradicated the disease in the course of six years, though the land was neither drained nor subjected to cultivation, and the dangerous meadows are now again pastured with impunity.
In the case of sick animals the greatest care is requisite to keep them from common drinking- or feeding-troughs; to exclude all other animals, even the smaller quadrupeds and birds, which may become the bearers of the poison; to avoid the chance of the drainage of infected excreta into other yards and pastures, and to carefully disinfect and guard the human attendants against contamination. The sale of animals out of an infected herd, and, above all, for the meat-market, and the use of the milk or other products of such animals, until attested sound, are highly reprehensible.
Finally, there are the different methods of protecting the system by inoculation with modified virus. The first of these is that of Burdon-Sanderson, Dugnid, and Greenfield, who in 1878 and 1879 inoculated six cattle with the blood of guinea-pigs dead of anthrax, all of which survived except an old, emaciated, worn-out, and pregnant cow, and all the survivors would only afterward contract anthrax in a mild form. The anthrax blood of the guinea-pig inoculated on the sheep proved fatal. The second mode is that of Pasteur, who cultivated the anthrax-germ artificially in flasks of meat-infusion, and after the nourishment in the latter had been used up left the bacilli to degenerate until their virulence had been so far decreased that the liquid could be safely inoculated on animals, so as to produce a mild anthrax infection and thereafter secure immunity from this poison. For all the larger domestic animals he found that the eighth day of the culture sufficed, provided there had been no formation of spores; and the method has now been applied on many scores of thousands of domestic animals. Klein, however, has found that cultures in pork-broth of the same age are invariably fatal to rodents, and that a guinea-pig which survived inoculation with culture a month old did not possess immunity against fresh virus. The third method, that of Toussaint, consists in heating the fresh virus, so as to lessen its activity, and then inoculating it on the animals to be protected. He found that a temperature of 55° C. (131° F.) maintained for one hour rendered the virus non-fatal, without impairing its prophylactic powers on animals inoculated. In spite of a partial failure at Alfort from insufficient heating of the virus, the method has now been firmly established as at once easy and effective.
The great value of these discoveries can hardly be overestimated, yet it is to be feared that the éclat of their reception has led to a far too general adoption of the methods. No one of the methods professes to destroy the life of the bacillus nor to impair its power of self-propagation. The bacillus, therefore, is likely to be planted in the localities where it is being employed, and, if the soil is favorable, to be perpetuated there. It follows also, from the susceptibility of the bacillus to change under varying conditions of life, that the modification impressed on it by the methods of Pasteur and Toussaint may be reversed under a reverse state of the environment, and that the harmless virus sown by our inoculators may in favorable soils produce the more deadly types. The methods secure the safety of the individual herd inoculated, at the expense of planting in the pasture a seed most perilous to all future uninoculated herds that may roam there. The only place for such protective inoculations is on pastures already charged with the anthrax bacillus, and from which that cannot be eradicated. On the dry, healthful soils where the bacillus cannot survive the inoculation is useless, while on the dense, damp, rich soils favorable to its preservation, but as yet uninfected or nearly so, this inoculation is but sowing deadly seed to secure a very temporary and questionable advantage.