Part 3

Cause. The essential cause is the bacillus of malignant œdema, the septic vibrio of Pasteur, bacillus septicus gangrenæ of Arloing, the bacillus of septicæmia gangrenosa of others.

Morphology. This is a staff-shaped microbe 3–4 μ. long by 1 μ. broad, often united in chains of three or more to form long flexuous filaments. They are furnished with numerous flagella by which they are rendered very actively motile. The movements are tardy or simply flexuous in the filaments. Spores form in the isolated bacilli (not in the filaments) in suitable culture media and at a temperature of from 20° to 38° C. They occupy a place near the centre of the bacilli, not the ends as in the bacillus of emphysematous anthrax. The bacilli are anærobic and die quickly in air, but the spores are unaffected by oxygen. The spores are similarly resistant to most disinfectants. They will grow readily in ordinary culture media if oxygen is excluded, for example under an atmosphere of hydrogen, nitrogen or carbon dioxide, and liquefy gelatine. Even the oxygen present in the circulating blood is highly inimical to them, so that they are rarely found in the blood during life, but rapidly invade both it and the tissues after death, and the suspension of respiration. In peptonised and glucosed gelatine the colonies are characterized as globules of liquefaction usually combined with gas. The germ is widely distributed in soils in general and not confined to limited areas like the bacilli of anthrax and black quarter.

Animals susceptible. The bacillus attacks man, horse, ass, goat, sheep, pig, mouse, Guinea pig, rabbit, white rat, cat, dog, chicken, pigeon, and duck. The mature ox is immune, but calves suffer. Dogs are often immune having already suffered from the disease. A first attack gives immunity from a second.

Infection Channels. Inoculation on an abrasion of the skin or surface sore is not usually infecting, the oxygen of the air destroying the germ. If, however, it is inserted deeply in the connective tissue, subcutem, it grows readily in a susceptible animal. Hence the danger of infection in deep wounds the recesses of which are not exposed to the air, and in such it becomes a most redoubtable surgical complication. If such wounds are the seat of active inflammation, with abundant exudate and more or less exclusion of the air-bearing blood, and in cases of blood stasis the field is specially inviting to the bacillus.

The debility of the injured tissue is a further invitation to the attack. Chauveau injected 4 to 5cc. of virulent liquid of malignant œdema into the veins of a ram and then practised bistournage, with the result that an invasion of malignant œdema of the scrotum and tunica vaginalis followed immediately. Pure cultures may be harmless, whilst an admixture of proteus vulgaris or micrococcus prodigiosus renders them most deadly (Penzo). Granulating wounds are even less favorable to invasion than simple abrasions. In these the bacillus cannot enter at once into the lymph channels and is exposed to destruction by the combined influence of the air and leucocytes.

Wounds in dropsical or gangrenous parts are equally favorable, to the development of the bacillus. Under such conditions the tissues are wanting in oxygen and resemble the condition of the entire body after death, when the bacillus of malignant œdema quickly penetrates its whole substance. Petri has traced the infection through the genital passages of newly delivered rabbits, producing a fatal metro-peritonitis and cutaneous œdema. A similar invasion may take place in other susceptible parturient animals. Lustig in a certain number of cases satisfied himself that he had traced the invasion through the intestine of the living horse. Invasion by the lungs, even by spores, is usually rendered impossible by reason of the presence of the inspired air.

A large dose of the virus is most likely to effect a successful invasion, since the toxins tend to debilitate and lower the defensive powers of the tissues and leucocytes. The effect of the toxins is shown under injections into the arteries, veins or trachea. A certain amount of hyperthermia follows, but there is rarely any colonization and reproduction of the bacillus in the connective tissue. In dogs and rabbits large doses given in this way induce short inspiration and broken or double expirations. In fatal doses death is preceded by extreme dyspnœa and convulsions. (Rodet and Courmont).

Lesions and Symptoms. The tissues where invasion occurs, become the seat of an abundant œdematous exudation, which feels boggy and painful and may even crepitate when pressed or manipulated. In case of an open wound, there is a profuse liquid discharge of a yellowish watery or serous aspect, and bubbles of gas or froth having a somewhat fœtid odor. The center of the swelling may become soft and flaccid while the peripheral parts where the disease is advancing are tense and resistant.

In fatal cases the mucosæ of the small intestine and lungs are usually the seats of œdema in which the bacillus is found. The bacilli may also be found in the liver. It is noticeable that gross lesions of the spleen and kidneys are usually absent, in marked contrast with anthrax. The microbes found in the tissues may be in the form of bacilli, micrococci (spores, or m. prodigiosus), and sometimes filaments.

Inoculation with a minimum dose usually results in local abscess only.

Diagnosis. From emphysematous anthrax, with which malignant œdema is most likely to be confounded, it is to be distinguished by its appearance anywhere outside the black quarter areas, by the immunity of cattle which are so obnoxious to emphysematous anthrax, by the susceptibility of man, who does not contract black quarter, by the formation of the spore near the middle of the bacillus in place of at one end, by its resistance to the action of ordinary disinfectants, and by the greater tendency to form filaments.

From anthrax it is differentiated by its appearance outside the anthrax localities, by the absence of the bacillus from the blood and from the surface layers of the skin, by the normal size of the spleen, and by the active motility of the bacillus. It cannot be cultivated like anthrax in the free air or on the surface of culture media, and unlike anthrax bacillus, its cultures produce bubbles or gas.

Treatment. This is essentially surgical and consists in free incisions to admit air freely to all parts of the œdematous tissue, perfect drainage and a liberal use of peroxide of hydrogen. Other disinfectants may be employed but are much less promising. The free disinfection of the adjacent skin is an important element in treatment.

Prevention. This consists essentially in the thorough disinfection of all accidental and surgical wounds, the careful cleansing and antisepsis of the skin before an operation, the exclusion of earth, manure, or water from driven wells or fountains, from all wounds, and above all the exclusion of proteus vulgaris, and micrococcus prodigiosus.

Immunity may be secured by a first, non-fatal attack of the disease.

INFECTIOUS FEVERS OF SWINE.

One name for several affections. Differentiation, swine erysipelas, hog cholera and swine plague. Complex infections. Effects of large, medium and small doses, of more or less potent germ, of greater or less susceptibility.

Until comparatively recent years the various infectious fevers of swine have been confounded and described as a single disease, the name varying in the different countries in which they were observed. In America it was Hog Cholera; in England, Swine Fever; in France, Rouget; and in Germany, Schweineseuche. A closer study showed a marked tendency to a particular class of lesions in different epizoötics, and bacteriological research associated plagues in given localities with different microbes, so that progress has been made in differentiating one from another to a certain extent.

The first clear distinction was made in setting aside the swine erysipelas (rouget, rothlauf,) from the rest as distinguished at once by its small, delicate bacillus, differing notably from the others in its staining and cultural peculiarities, as well as in the predominance of the cutaneous lesions.

What remains after eliminating erysipelas, constitutes a group having so much in common that attempts at further differentiation have led to much disputation, and not even to-day is there such accord in different countries as the writer of a text-book would find desirable. One class of pathologists claims but one common disease with many varieties under different conditions, just as the term septicæmia or blood poisoning has been made to designate a whole class of local and general infections, irrespective of the particular microbes that cause them. Others with greater precision give the disease a name according to the causation by one particular microörganism, or by another, which may be closely related to it in many respects, but which in successive subjects and outbreaks, maintains its own individual characteristics as regards morphology, cultural and staining habits, pathogenesis, etc. The question has been rendered all the more trying, by the occasional association in the same animal system, or in the same outbreak of two distinct varieties of microörganisms, in place of one, giving rise of course to modifications in the symptoms, lesions, progress, mortality, etc.

Apart from the microörganism the whole class tends to show a close family relationship in their pathological phenomena shown under different conditions :

1st. Under a large dose, or specially virulent germ, in a particularly susceptible animal, all tend to a manifestation of an acute septicæmia, with generally diffused petechiæ of the skin, mucosæ, serosæ and internal organs, blood extravasations, and an early high mortality.

2d. Under a smaller dose, or a less potent germ, or in a less susceptible animal the tendency is to necrotic processes in the seat of inoculation or the point of election of local lesions. Necrotic ulcers are especially common in cases that survive one, two or three weeks, or that develop in a subacute or chronic form.

3d. With a minimum dose of a germ of little potency, and in a very resistant subject even the necrotic lesions may be absent, and there may be suppuration only or ulceration of serosæ and joints.

The question of the primary identity, or disparity of the whole class of germs, causing the septicæmic swine plagues, may be practically ignored in this work; it is important rather with our present knowledge to note the diseases associated with particular germs, or varieties of germs, and to describe these as far as possible as independent affections. This is as permissible as it is to describe smallpox, sheeppox, and cowpox as distinct affections, no matter what may be the truth or falsity as to their alleged original identity.

Rouget in Europe and Hog Cholera and Swine Plague, as the best established types in the United States deserve primary mention, to be followed by references to additional types which have been found to be associated with other distinct microörganisms.

ROUGET, ROTHLAUF. RED FEVER OF SWINE. SWINE ERYSIPELAS.

Definition. Comparative immunity of sucking pigs. Disease unknown in America. Causes: Bacillus erysipelatos suis, mature age, infection through yards, buildings, troughs, dust, mice, rabbits, pigeons, men, dogs, vermin, birds, butcher’s and kitchen scraps, swill, hot weather, damp seasons, close pens, movement of swine, stockyards, fairs, public conveyances, public highways. Symptoms: incubation three days, chill, violet mucosæ, hyperthermia, recumbency under litter, muscular weakness especially behind, inappetence, thirst, costiveness, later diarrhœa, tenderness to touch, lymph glands swollen, red, blue, violet or black discoloration of skin, cutaneous swelling and pitting. Course: death in 12 hours to 6 days, or convalescence prompt. Mortality 20 to 80 per cent. Lesions: congestion of capillary vessel, blood extravasations, petechiæ, affecting cutis and subcutaneous fat, lymph glands congested, discolored; lungs engorged; spleen enlarged, liver and kidneys congested, petechiæ general, blood little altered. Bacillus 1.5 μ, anærobic, easily destroyed in pens, in pork. Pathogenesis: swine, rabbits, mice, rats, pigeons and sparrows suffer. Rabbit germ less fatal to pigs. Immunization, advantages and drawbacks. Technique.