ANTHRAX, the name of a disease oc curring epidemically among herbivora, chiefly oxen and sheep, and occasionally affecting man. It is also called malignant pustule, splenic fe ver, wool-sorters' disease, charbon, milzbrand. It is caused by a rod-shaped bacterium, the Bacillus anthracis, first seen in 1849 and iso lated in 1863, and conclusively proved by Koch in 1876 to be the cause of the disease, this be ing one of the first diseases demonstrated to be caused by bacteria.
In man the bacillus is usually acquired by handling the hide of an animal having died from the disease. A local lesion, the malignant pustule, is formed, and this may lead to wide spread infection with oedema and lymphatic in vasion, attended by fever, gastro-enteritis, col lapse, and death. The infection may remain lo calized, however, and the patient may recover. Less often the infection takes place in the res piratory tract, the patient having breathed the bacillus in the dust arising from handling hides or sorting wool; in such cases a rapidly fatal form of hiemorrhagic oedema may develop. A still rarer form of the disease in man affects the intestinal tract. The bacillus of anthrax is one of the largest of the pathogenic bacteria. It is 6-8 microns j 6-8inches long and 1.5 25,000 microns thick, being a sort rod with square edges, and growing in chains. The protoplasm is finely granulated and it forms spores about the centre of the bacillus. It grows very rap idly on all of the commonly used bacteriological culture media, best at a temperature of 35° C., but its multiplication ceases at temperatures be low 12° C. or above 45° C. The bacilli are readily killed by temperatures of 60° C., but the spores are very resistant, and dry heat at 140° C. must be applied for several hours to kill them. In a dry condition they remain via ble for several years and will resist boiling water for at least five minutes. The gastric juice also does not destroy them readily. The bacteria are found in the blood and throughout the organs of animals dying of anthrax. They are particularly numerous in. the spleen and in the lymphatic structures. They poison the body by the development of a toxin or toxins which in turn cause degeneration of the tissues of the body.
Anthrax is one of the diseases in which a serum therapy was instituted early. Thus far it has not proved of signal service, although a protective serum has been made by which ani mals may be immunized against the disease.
Anthrax in animals is a comparatively com mon disease, affecting sheep, cattle and, more rarely, horses and members of the deer family. It is rare among the carnivora. The disease is not geographically confined, and animals in vari ous parts of the world are affected by it. It is naturally less common in countries in which there is some legislative control, and rarer at present than in former times. In Britain the mortality is small; in France, at one time, as many as 10 per cent of the sheep died annually of anthrax. Since the modern method of im munizing cattle has been introduced the mor tality has been much lessened. The symptoms vary widely, but at least three marked groups are observable. In some instances the affected animal develops symptoms of extreme collapse; it drops to the ground; the pulse and respira tion are quickened, there is difficulty in breath ing and the animal dies in convulsions within a comparatively short time. A commoner type
of attack is begun by symptoms of general dis tress, the animal is ioff its feed,') the pulse and respiration are quickened, chills develop, the temperature rises to 103 or 104° F., bloody diarrhoea occurs, bloody nasal catarrh. There then may develop convulsive movements; there is rapid loss of strength, and the animal may die in from 10 to 48 hours, sometimes at the end of three to four days. A third type is char acterized by a slow onset, the lymphatic struc tures are involved, they swell and form car buncles, which may ulcerate. General symp toms of infection may develop— the spleen may enlarge, bloody discharges are common and the animal dies of generalized tuemorrhagic oedema. The diagnosis is readily made in all cases by a microscopical examination of the blood. Differ ent animals show marked variations in suscep tibility. The sheep, save Algerian, ox, guinea pig and mouse, are all very susceptible, but the goat, horse, deer and pig are less often attacked. Man may be placed next in the order of liabil ity; the white rat, adult carnivora, birds and amphibia are immune. The disease is conveyed to animals largely by way of the intestinal canal. The bacilli are ubiquitous in the grass and hay about an infected area.
Preventive Pasteur first evolved a method of inoculation by an attenu ated virus, a sort of hardening the animal, as it were, that subsequently made it resistant to the virile bacteria. Although other methods, notably the use of anti-anthrax serum, have been used, the attenuated virus method seems to give the best results. Surgical methods are the only mode of treatment for man. Thorough sterilization of hair, wool and animal skins by dry heat, steam or by chemical agents is now generally adopted to prevent the infection of man from these sources.
Pasteur's method was the injection of a cul ture attenuated by 24 days' growth at a tempera ture of 42.5 C., followed in 10 days by an in jection of a culture attenuated by a growth of but 12 days at the same temperature. The Dawson method, invented in 1911, is the injec tion of a single vaccine, differing from that of Pasteur only in degree of attenuation. It is used when animals are dying from the dis ease and immediate protection is required. A passive immunity lasting from one to two weeks is thus secured within a few hours.
Pollender, Viertel ahr schrift f fir Gerichtliche Medicin, VIII' ; Davaine, 'Comptes Rendus Acad. des (57, p. 220 et seq.) ; Koch, 'Cohn's Beitrage) (Vol. II, 1876). For later literature see Fliigge, 'Die Mikroorganis men' ; Hoare, 'A System of Veterinary (Chicago 1913) ; Sternberg, 'Man ual of Bacteriology,' and the following re ports issued by the Bureau of Animal Indus try, United States Department of Agriculture: 'Special Report on Diseases of Cattle' (Wash ington 1912) ; Washburn, H. J., 'Anthrax with Special References to Its Suppression' (Lb. 1909) ; Dawson, C. F., 'Anthrax with Special Reference to the Production 'of Immunity.'