In the lungs the pleuræ and subpleural and interlobular tissue are extensively infiltrated and thickened by a profuse yellowish serous or sero-sanguineous exudate, so that the appearance may closely resemble that of lung plague. The lung tissue is consolidated, hepatized and dark red, with at some points emphysema. The pleural sac is usually filled by a serous or bloody effusion (2 to 25 quarts) and there is often extensive implication of the pericardium. The tracheo-bronchial mucosa and bronchial glands show extensive infiltration and thickening.
In the abdomen are found extensive infiltrations and blood extravasations in the mucosa and submucosa of the stomachs and intestines, softening and shedding of the epithelium, infiltrations of the peritoneum, diaphragm, and sublumbar adipose tissue, and softening and degeneration of the liver and kidneys. The intestinal gastric and mesenteric glands are usually infiltrated, softened and blood-stained. Engorgement of the spleen is exceptional.
The blood is very black but not usually materially changed in consistency nor coagulability. Petechiation of the different serosæ and other tissues is a prominent feature.
In chronic cases the lesions are mostly shown in the lungs and lymph glands. The lungs show circumscribed lobular islets of congestion, induration or caseation, offering a suggestion of tubercle, which is all the more deceptive when cretifaction has set in. The caseous centres may vary in size from a pea to a walnut, and some may have ruptured to form a vomica discharging into a bronchium. Bronchia leading to affected lobules are blocked with muco-purulent matter, yellowish, thick and tenacious, and their mucosa is thickened and puckered. The enlarged lymph glands are especially those of the bronchia, trachea, mediastinum, bowels, mesentery and sublumbar region.
The bacillus is present in the exudate but is especially abundant in the blood, and in the chronic cases in the bronchial mucous.
Diagnosis. From anthrax (gloss-anthrax) this affection is easily distinguished by the absence from the blood and exudates of the large, square ended anthrax bacillus, by the absence of enlargement and blood engorgement of the spleen, and of the softness and diffluence of the blood clot which characterize anthrax. Swine which are with difficulty inoculated with anthrax are very susceptible to hæmorrhagic septicæmia. Sheep which are very receptive to anthrax are somewhat refractory to the disease now in hand. Pigeons resist anthrax but readily contract septicæmia hæmorrhagica.
From black quarter it is readily distinguished by the absence of emphysema and crepitation and of a secondary cooling in the external swellings, by the presence of the germ in abundance in the blood, by its smaller size, its bipolar staining, and its lack of motility and of spores. Inoculation with black quarter bacillus kills the guinea pig, but spares the pigeon.
From lung plague it is distinguished by the suddenness of its attack and rapidity of its progress to a fatal issue; by the usual coincidence of skin and bowel lesions, while the lung plague affects the chest only; by its communicability to pigs, sheep, pigeons, and even horses, which are all immune from lung plague; and by the usual absence of lung lesions of different ages, which are so characteristic of lung plague. The abundance in the blood of the cocco-bacillus with bipolar staining in hæmorrhagic septicæmia is characteristic. Lung plague spreads slowly to exposed cattle, but spares all other domestic animals.
From Rinderpest it is differentiated by the history of its advent, by the presence of the surface œdematous swellings, by the absence of the whitish epithelial concretions on the mouth or vulva, and of the deep dark portwine discolorations of the mucosæ of the mouth, rectum and vulva, and by the fact of its inoculability on domestic animals generally. Rinderpest spreads rapidly to all exposed ruminants, but spares pigs, rabbits, Guinea pigs, horses and birds.
From malignant œdema it differs in its inoculability on the surface in place of subcutaneously only, in the presence of the cocco-bacillus in the blood during life, whereas in malignant œdema the germ is confined to the local lesion, in the absence of crepitation, which may be present in the swelling of œdema, in the greater facility with which cultures can be made of the septicæmic cocco-bacillus and in the absence of gas production in such cultures. The malignant œdema comes from a single accidental deep inoculation from almost any rich soil, and is not a malady spreading widely and generally on given limited damp, rich lands which have become infected. Finally the cocco-bacillus of septicæmia hæmorrhagica is found singly in the blood or exudate, whereas the microbes of malignant œdema may be found in form of sporeless filaments intermingled with the bacilli.