Text Book of Veterinary Medicine, Volume 4 (of 5)

Part 1

TEXT BOOK OF VETERINARY MEDICINE

JAMES LAW, F.R.C.V.S.

Director of the New York State Veterinary College Cornell University, Ithaca, N. Y.

VOL. IV.

INFECTIOUS DISEASES.

ITHACA PUBLISHED BY THE AUTHOR 1902

Copyright by JAMES LAW 1902.

PRESS OF ANDRUS & CHURCH ITHACA, N. Y.

VETERINARY MEDICINE.

PYÆMIA AND SEPTICÆMIA.

Multiplicity of Septicæmias. Pyæmia and Septicæmia, distinction between. Multiple secondary abscesses in pyæmia; no secondary abscesses in uncomplicated septicæmia. Septico-pyæmia. Pyæmia. Causes: bacteria, deep wound infection, susceptibility, debility, shock, illness, narcotic ptomaines, partial immunization, complexity of infection, mutual decomposition of toxins, dose, lesions of intima of blood vessels, thrombosis, embolism, action of microbes on hæmatoblasts and blood globules, viscidity of cells, adhesion to endothelium, coagula, solution of clot, escape of microbes. Lesions: wound, abscess, thrombus, emboli, infarction, abscesses, ulceration, endocarditis. Spleen. Blood coagulates. Symptoms: rigor, hyperthermia with remissions, pulse weak, soft, rapid, perspiration, diarrhœa, sweet breath, fæces, urine acid, dulness, prostration, mucosæ dusky or yellow, blood shows leucocytosis, hæmolysis, cardiac murmur, arthritis, stupor, coma, palsy, dry, puffy sore, source of infection. Prognosis grave. Prevention: largely surgical, antisepsis, asepsis, excision of infected vein. Treatment: antiseptics, locally and internally, stimulants, tonics, nourishment. Septicæmia: microbes, toxins, septic intoxication, septic infection, fermentation fever, sapræmic fever. Lesions: blood dark, incoagulable, spleen enlarged—gorged, petechiæ, cloudy swellings, coagulation necrosis, organs as if parboiled, congested glands, kidneys. Symptoms: chill slight, hyperthermia without marked remissions, weak, rapid pulse, hurried breathing, anorexia, emesis, yellow mucosæ, nervous disorder—dulness, apathy, stupor, paraplegia. Value of precursory conditions. Prognosis grave. Prevention, Treatment: remove source of poison, antiseptics, drainage, internal antisepsis, strychnia, quinine, iron chloride, stimulants, supporting, easily digestible food, sponging.

At first introduced to indicate the supposed results of pus and septic material respectively in the blood, these terms have come to represent the clinical phenomena which come from the introduction into a susceptible system of pyogenic and necrogenic microbes and their toxic products. Gradually different affections, which would have been included under the same general terms, came to be identified under specific names, and a number of these will be described as individual diseases—strangles, mouse and rabbit septicæmias, metritis, phlebitis, omphalitis, rouget, barbone, chicken cholera, septicæmia hæmorrhagica, etc.—yet a certain number have been left to be referred to under the generic terms, though respectively due to different microbes.

Distinctions between Pyæmia and Septicæmia. Pyæmia is a morbid condition characterized by the formation in different organs of multiple metastatic abscesses, dependent on the transference, in the blood stream, of infected clots, or particles containing pus microbes, and their arrest at distant points, so as to cause foci of suppuration commencing with the intima of the vessels.

Septicæmia indicates a general infection often by the same microbes, but showing its results in enlargement and blood engorgement of the spleen and lymph glands and necrotic foci of the liver, kidneys and other organs, but without the formation of multiple abscesses. The presence of the microbes in the different organs affected, shows that it is not due to the diffusion of the toxic chemical products alone, as at one time supposed, and the lack of abscesses appears to be due to the absence of clots or of modified and adhesive leucocytes or hæmatoblasts, which adhering to the epithelium of the vessels predispose to suppuration.

The two conditions are, however, often combined, constituting what is known as septico-pyæmia.

As in the occurrence of other infecting diseases, the condition of varying susceptibility must be taken into account, one individual, or one species resisting an inoculation which would be deadly to another.

=Pyæmia.= Causes. The causation microbes are most commonly staphylococcus pyogenes aureus, or albus, the streptococcus pyogenes, and less frequently bacillus pyocyaneus, bacterium coli commune, and probably any pus producing microbe. Many conditions must however be accepted as contributing to the general infection.

Inoculation on a mere abrasion or surface sore is not to be dreaded so much as if the virus is lodged subcutaneously or in a deep wound. The ready escape of the toxic products, the active leucocytosis which takes place in the granulations, and the action of the oxygen of the air are more or less protective in the exposed sores.

The native susceptibility of the subject,—horse, ox,—conduces to the disease, while the insusceptibility,—bird—tends to obviate it.

The debility of the system or of individual tissues attacked, lowers the resistant power, and especially that of leucocytosis, and thus favors survival and encrease of the microbes and their chemical products. Thus the shock succeeding a serious operation, the general depression attendant upon severe illness, or the poisoning by narcotizing ptomaines and toxins, may easily become the extra weight which causes the system to succumb. On the contrary, pre-existing or long standing disease, with consequent general debility appears at times to prove to some extent a protective factor, the previous exposure to the invading germ having educated the leucocytes to resist the toxins and to produce the defensive sera which neutralize the latter or keep the invading microbes in check. A measure of immunization has been secured.

The resulting immunization cannot be looked on as very perfect, nor permanent, as a specially strong inoculation by a virulent microbe, or large dose, or different conditions of life, will entirely overcome it, and the pyæmic fever appears. Yet in chronic cases of secondary abscesses from a deep source of infection, the resistance is often such as to ward off febrile pyæmia. In a horse with primary abscess situated deeply under the humerus, free evacuation and healing of the wound, have, in my experience, been followed by the formation of abscesses in distant points for a period of seven years, but without any marked febrile reaction.

The complex nature of the infection appears at times to overcome the vital resistance more effectively than will the presence of even a potent microbe alone. Some of the worst cases follow on a wound, the seat of complex infection, and even saprophytes are to be dreaded in this connection. This may operate in various ways, either by mutual combinations or decompositions of the toxic products of associated germs producing more deleterious products, or by the individual action of one ptomain or toxin on leucocytes, hæmatoblasts, sera, or tissue, laying it more open to the attacks of those of another microbe which by itself would have been comparatively harmless.

Koch’s experiments showed that the attack is violent in ratio with the size of the dose: one-thousandth part of a drop of pyæmic blood was harmless to the rabbit, while one tenth of a drop killed in one hundred and twenty-five hours, and a syringe full in forty hours.

In ordinary cases of pyæmia the occurrence of internal phlebitis or arteritis with the inevitable thrombosis is an important step in causation. Any inflammation of the inner coat of the vessel leads promptly to the formation of a coagulation of the contained blood, and blocking of the lumen. Beginning on the diseased or abraded surface, the clot forms backward along the line from which the blood normally comes (proximal in the arteries; distal, in the veins), until it reaches the next considerable colateral branch. The clot is firmly adherent to the intima except at the free end, which is conical and projects into the blood current.

If small portions are detached from the thrombus and washed on in the blood stream they become arrested when they reach a vessel too small to admit them, it may be a smaller artery, or it may be a capillary, and always in the line of the circulation,—from the systemic circulation to the lungs, or from the lungs to the system at large. This is =embolism=. Wherever arrested, the contact of the leucocytes and hæmatoblasts with the inner coat of the vessel, leads to metabolic changes and firm adhesion, and the pus microbes in the clot determine suppuration and abscess.

Eberth and Schimmelbusch have shown that the hæmatoblasts, even more than the other blood elements, when acted on by the pus microbes become viscous and stick not only to each other, but to any floating body, and to the inner serous coat of the vessel, particularly when the latter has been abraded or injured. This clumping together of the hæmatoblasts forms white clots which block the smaller vessels, but in the viscous condition they further the coagulation of the fibrine, and again when they come in contact with the intima, instead of passing through, or moving on, they remain adherent and start the formation of thrombi. This is above all common in given tissues, and the medulla of bone has in this respect a bad preëminence, so that acute suppurative osteomyelitis, is a familiar lesion and is liable to become chronic, and determine distant abscesses and general infection long after.

The thrombus thus formed is an infective coagulum, tending to constant encrease, as the clot is a favorable culture-field for the microbes, and the tendency is to coagulate more and more of the adjacent blood. It tends further to disintegration, as the action of the microbes and their toxins on the leucocytes, transforms these into pus cells, inducing softening of the mass, and the washing on of individual infective pus cells and minute portions of the clot to form infective centres and abscesses at distant parts.

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