Fig. 27.—Bacillus of Anthrax in section of skin, from a case of malignant pustule; shows vesicle containing bacilli. × 400 diam. Gram's stain.
Clinical Varieties of Anthrax.—In man, anthrax may manifest itself in one of three clinical forms.
It may be transmitted by means of spores or bacilli directly from a diseased animal to those who, by their occupation or otherwise, are brought into contact with it—for example, shepherds, butchers, veterinary surgeons, or hide-porters. Infection may occur on the face by the use of a shaving-brush contaminated by spores. The path of infection is usually through an abrasion of the skin, and the primary manifestations are local, constituting what is known as the malignant pustule.
In other cases the disease is contracted through the inhalation of the dried spores into the respiratory passages. This occurs oftenest in those who work amongst wool, fur, and rags, and a form of acute pneumonia of great virulence ensues. This affection is known as wool-sorter's disease, and is almost universally fatal.
There is reason to believe that infection may also take place by means of spores ingested into the alimentary canal in meat or milk derived from diseased animals, or in infected water.
Clinical Features of Malignant Pustule.—We shall here confine ourselves to the consideration of the local lesion as it occurs in the skin—the malignant pustule.
The point of infection is usually on an uncovered part of the body, such as the face, hands, arms, or back of the neck, and the wound may be exceedingly minute. After an incubation period varying from a few hours to several days, a reddish nodule resembling a small boil appears at the seat of inoculation, the immediately surrounding skin becomes swollen and indurated, and over the indurated area there appear a number of small vesicles containing serum, which at first is clear but soon becomes blood-stained ([Fig. 28]). Coincidently the subcutaneous tissue for a considerable distance around becomes markedly œdematous, and the skin red and tense. Within a few hours, blood is extravasated in the centre of the indurated area, the blisters burst, and a dark brown or black eschar, composed of necrosed skin and subcutaneous tissue and altered blood, forms ([Fig. 29]). Meanwhile the induration extends, fresh vesicles form and in turn burst, and the eschar increases in size. The neighbouring lymph glands soon become swollen and tender. The affected part is hot and itchy, but the patient does not complain of great pain. There is a moderate degree of constitutional disturbance, with headache, nausea, and sometimes shivering.
If the infection becomes generalised—anthracæmia—the temperature rises to 103° or 104° F., the pulse becomes feeble and rapid, and other signs of severe blood-poisoning appear: vomiting, diarrhœa, pains in the limbs, headache and delirium, and the condition proves fatal in from five to eight days.
Differential Diagnosis.—When the malignant pustule is fully developed, the central slough with the surrounding vesicles and the widespread œdema are characteristic. The bacillus can be obtained from the peripheral portion of the slough, from the blisters, and from the adjacent lymph vessels and glands. The occupation of the patient may suggest the possibility of anthrax infection.