Part 142

{926}

ANTHRAX (MALIGNANT PUSTULE).

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

SYNONYMS.--Latin, Ignis Sacer, Anthrax Epizoöticus, Pustula Maligna, Pustula Pestifera, Erysipelas Carbunculosum, Carbunculo Contagioso, Glossanthrax, Angina Carbunculosa, Anthrax Hæmorrhoidalis, Mycosis Intestinalis, Apoplexia Splenitis, etc. English, Black Erysipelas, Malignant Vesicle, Anthrax Fever, Splenic Apoplexy, Splenic Fever, Inflammatory Fever, Carbuncular Fever, Black Quarter, Blood-Striking, Bloody Murrain, Blain, etc. French, Pustule maligne, Charbon, Fièvre putride, Typhohémie, Pélohémie, Mal de Rate, Splenite Gangréneusé, etc. German, Karbunkelkrankheit, Contagiose Karbunkel, Milzbrand, Milzseuche, Milzbrandfieber, Brandbeulenseuche, Rothlauf, etc. Russian, Jaswa (boil-plague). Italian, Antrace. Spanish, Carbunculo, Lobado. Swedish, Boskapssjukan. Mexican, Calentura del piojo.

DEFINITION.--Anthrax is an acute, infectious, bacteridian disease, occurring mostly in the Herbivora and Omnivora, but communicable to other mammals (including man), to birds, and even fishes. Its local manifestations are exceedingly varied in kind, but the malady is characterized by the presence in the tissues or blood, or both, of specific spherical and linear bacteria (micrococcus and bacillus anthracis), leading to arrest of hæmatosis, to disintegration of the blood-globules, to sanguineous engorgement of the spleen, to capillary embolism, and to a spreading gangrenous inflammation.

HISTORY AND GEOGRAPHICAL DISTRIBUTION.--While ancient history is not clear as to the specific diseases of animals, yet there is the strongest presumption that nearly all great plagues that attacked indiscriminately animals and man were of this nature. Thus, the plague of murrain, with boils and blains breaking out on man and beast, in the days of Moses, was probably of this kind (Gen. ix. 3.); also that which at the siege of Troy extended from animals to man, and many later epizoötics in all parts of the world. No infectious disease of man and animals, with the single exception of tuberculosis, has been more widely diffused, and none can be considered as more cosmopolitan. Heusinger, in his classic work on Milzbrandkrankheit, traces the ravages of the disease from the highest to the lowest latitudes in the northern and southern hemispheres and in the Old World and the New. He adduces outbreaks in Siberia, Astrakan, Lapland, and Finland, in Russia, Prussia, Poland, Silesia, Bavaria, Holland, Belgium, France, Spain, Portugal, Italy, Switzerland, Austria, Hungary, Greece, Turkey, Egypt, East and West Indies, {927} North and South America, etc. We can now add all the great English, French, and other European colonies not included in the above (South Africa, Australia, New Zealand, Algeria, etc.), together with China and Japan. We find, moreover, that the disease is always most prevalent where agriculture is in its most primitive condition, so that there can be little doubt of the prevalence of the affection in the less-civilized countries as well. But while the disease is prevalent in all parts of the world, its ravages are largely subordinate to the nature of the soil. Wherever this is close, impervious, marshy, or charged with an excess of organic matters, the gaseous emanations of which drive out most of the oxygen, the anthrax-germs, once introduced, tend to be preserved indefinitely. Thus, in drying up basins with no natural drainage, on lake and river margins, on deltas, in forests, in mucky, mossy, or peaty soils, and on those that are habitually over-manured, the germs of anthrax are especially liable to be perpetuated. It has long been noticed that herbivorous animals are the most susceptible to anthrax, while the purely carnivorous, and to a less extent the omnivorous, have relatively a far higher resisting power. That the immunity is largely due to the food is manifest from the experiments of Feser on rats. Those fed on vegetable aliment contracted anthrax readily from inoculation, while those kept on an exclusive diet of flesh successfully resisted. The same rats that escaped while on a flesh diet were afterward placed on a vegetable diet, and then perished after inoculation. Davaine found the same to be true of foxes kept on meat and vegetables respectively, and inoculated with the virulent blood of the allied disease, septicæmia. He found, moreover, that guinea-pigs were much more susceptible to anthrax than rabbits. One-thousandth of a drop of virulent anthrax blood invariably killed the guinea-pig, while it left the rabbit unharmed. Klein has never found a rabbit insusceptible. It has recently been claimed that pigs are insusceptible, but I have known of many instances in which the offal of anthrax cattle, when devoured by pigs, has determined fatal anthrax in the latter. Chickens too prove much less susceptible to anthrax than the Herbivora. Inoculations made by Cohn and others proved invariably unsuccessful, while Pasteur has showed that they can be infected easily after the body has been cooled by partial immersion in cold water. Pasteur attributes this immunity to their normally high temperature, yet rabbits, sheep, pigs, wolves, and foxes, though maintaining a correspondingly high temperature, are still subject to anthrax. Even the herbivorous mammal suffering from acute anthrax fever has its temperature raised to that of the chicken, yet the disease progresses none the less surely to a fatal result. Again, anthrax liquids inoculated under the skin of a fox proved harmless, while if thrown into the warmer peritoneal cavity they proved fatal. It may well be suspected that the relative insusceptibility of chickens is in part due to the large amount of animal food consumed by them, and that the chilling process increases the receptivity by deranging sanguinification and nutrition.

The insusceptibility to anthrax is often characteristic of certain individuals or families or of the animals living in a particular district. Thus, Chauveau found that some French sheep, and nearly all Algerian ones, {928} resisted inoculation with a moderate amount of anthrax virus, while the introduction of a maximum amount proved fatal to these as to others. In the same way, it is often noticed that animals living in an anthrax region escape the evil effects of the poison, while strange animals brought in either fall ready victims or for a time do badly until they have become habituated to the locality. In view of the subsequent protective effect on the system of a first and non-fatal attack of anthrax, it is probable that all these examples of immunity in the Herbivora depend on a previous mild attack of the same disease or on the extinction of the more susceptible races. Even in the case of the animals that do badly on first coming into an anthrax district, and recover better health with immunity later, we may well infer that a mild form of the anthrax infection has been passed through.

ETIOLOGY.--The one essential cause of anthrax is the introduction into the system of a specific bacteridian germ (bacillus anthracis or its spores). This is not, as a rule, carried far on the atmosphere, but demands for its propagation contagion, immediate or mediate. Unless, therefore, it meets in the soil the conditions necessary to the preservation and propagation of the germ, it is transmitted with some uncertainty from animal to animal, and thus the disease does not spread widely and rapidly, like an ordinary plague, but tends to become localized in particular districts as an enzoötic.

But its dangers are none the less real nor its existence less to be dreaded. In predisposed localities, where the disease-germ has gained a footing, the animal mortality may exceed that caused by the great plagues, while the risk to human beings is incomparably greater than from any other acute infectious disease of the lower animals. Thus, in San Domingo, in 1770, 15,000 people perished in six weeks from eating the carcases of anthrax animals, and the mortality was only arrested when the meat was legally interdicted. In the worst anthrax years on some of the Siberian steppes as many as one-fourth of the whole human population suffer from the malady. The prevalence and death-rate, however, vary greatly in different localities and seasons. Sometimes only one or two solitary cases of the affection are observed; at other times the disease becomes moderately prevalent, but a lack of virulence in the poison or a previously acquired insusceptibility of the individual protects the great majority of the animals exposed, while at others, still, the poison attacks nearly all exposed to its contagion.

The animal products that mainly convey the disease are the blood, the liquid exudations, portions of the diseased carcase, and the bowel dejections. The virus is most potent when derived from an animal still living or only recently dead, yet under certain conditions (with spore-formation) it may long retain its virulence under the most extreme changes of climate, temperature, dryness, and humidity. Russian hides tanned in England or America frequently convey anthrax, which is known especially as a tanner's malady, and wool and hair sent from Buenos Ayres have repeatedly produced malignant pustule (woolsorter's disease) in Britain and the United States. The preserved scabs of malignant pustule have been often successfully inoculated on the lower animals, so that, like other forms of poison, this seems to be preserved indefinitely by desiccation.

The simple contact of the virus with the slightest abrasion will suffice {929} to convey the disease. It has often been communicated where no lesion of the epidermis could be found, yet the presumption is that even in such cases the cuticle had been in some way wounded. Eating the flesh of animals killed while suffering from anthrax has often conveyed the disease. In an outbreak in Swineshead, Lincolnshire, England, in 1863, I found a dog and a number of swine suffering from eating the bodies of dead bullocks. In 1864 an East Lothian (Scotland) farmer fed his pigs with the offal of a slaughtered anthrax bullock, and lost nearly the whole herd. The carcase of the bullock had been sent to market. About 1860 cattle, and even horses, died yearly on a swampy meadow at Brighton, Mass. On one occasion the owner, John Zoller, fed the offal of a dead bullock to his pigs, which were speedily attacked with anthrax, and as speedily killed to save their bacon (Dr. Thayer). Even when cooked the flesh is not always safe. Of this we have the undoubted case in San Domingo above noticed, the alleged death of 60,000 people in the vicinity of Naples from the same cause in 1617 (Kircher), and the thousands that die on the Russian steppes every anthrax year from eating the sick horses (Rawitch). But in all these, and in the ever-recurring cases in which families suffer from eating anthrax meat, there is the possibility, if not the probability, of the contamination of the meat subsequently to cooking by the knives, forks, tables, and dishes used. The San Domingo slaves had few appliances for cleanliness, much less disinfection, and the Tartars eat their meat from the same board on which it has been chopped up raw.

In accurate experiments it has been found that the bacilli are destroyed by a temperature of 145° F. maintained for five minutes, but the spores are capable of surviving the boiling temperature for five or even ten minutes. The varying power of resistance may be compared to that of the green stalk of the pea and the dry flinty seed. The first is destroyed by a very moderate heat, while the second will sprout after having had boiling water poured over it. The resisting bacillus-spores are never found in the living animal, but may be developed in the blood and tissues after death, and may account for the occasional extraordinary viability of the poison when exposed to a boiling temperature.

Milk, though often used with impunity, conveyed the disease when inoculated by Bollinger, and the same was true of the vaginal mucus. Innocent in the early stages of the disease while the germs are still localized, they become virulent after the bacilli swarm into the blood.

Healthy men and animals often carry the poison, though themselves insusceptible. The question of its conveyance by insects has been much debated, but the constant occurrence of malignant pustule on the uncovered parts of the body goes far to settle the question. Bourgeois long ago noticed that it was most frequent on the face, hands, neck, and arms, and rare on the trunk. In sixty cases recorded by A. W. Bell of Brooklyn, all occurred on the face except two on the hands, one on the wrist, and one on the forearm. The bite of a fly or mosquito had in many of these cases proved the starting-point of the malady. Bollinger has shown the presence of the bacillus in the stomach of such flies as fed on flesh and blood (horse-flies, bluebottles, etc.), and, together with Raimbert and Davaine, has produced anthrax by inoculations with the stomachs, legs, and proboscides of these insects.

{930} Surgical instruments occasionally convey anthrax. At Cockburnspath, East Lothian, Scotland, a yearling heifer contracted anthrax, and the whole herd was bled, commencing with the sick one. Next morning seven were found dead, the disease in each case extending around the fleam-wound. At Brunt, in the same county, a shepherd skinned an anthrax bullock, and after washing and taking a turn among his sheep, on the same day castrated several litters of pigs, all of which perished. In St. Lawrence Co., N.Y., in 1870, a surgeon inoculated himself while opening a vesicle on the hand of a farmer.

Harness, stables, stable utensils, vehicles, fodder, and litter are frequent bearers of contagion. At Geneseo, N.Y., in 1877, three horses and a cat died in midwinter after licking the blood from a stone-boat which had conveyed the skin of an anthrax bullock to market. Green fodder or hay harvested from ground formerly occupied by anthrax victims or from their graves often convey the poison, but probably only by the adherent earth and dust containing the anthrax-germ.

That the anthrax bacillus and its spores may be long preserved in earth is abundantly proved. At Avon, N.Y., nine months after any cases of the disease, the liquid leaking out on the river-bank near to the grave of a victim of the year before was licked by six cattle, and in two days they all perished. On the same pasture victims were seized yearly for seven years, but with a rigid seclusion of these, their products, and their graves the malady has finally disappeared. The persistent deadly effect of some soils on animal life, apart from the presence of the carcases, seems to show that in certain soils we find the normal home of the anthrax bacillus, while the migration into the animal economy is but an accident of its existence. The soils that are especially subject to anthrax are the dense clays, the limestones, and the rich alluvials. Among the essential conditions are the exclusion of oxygen, excepting a limited amount bearing some relation to what is found in the animal fluids, and the abundance of some alkaline agent (lime, potash, soda, ammonia), so that the earth is either neutral or only very slightly alkaline or acid. An acid vegetable infusion is inimical to the germ, which soon disappears from such a medium. The requisite paucity of air is found in all the dense, less pervious soils (clays, etc.), in soils habitually waterlogged (swamps, deltas, river-bottoms, low meadows, natural basins, drying lakes and ponds), and in soils rich in decomposing organic matter (peat, alluvial, over-manured). The antacid is often found present as lime or potash, or is constantly being produced in the form of ammonia, etc. by organic decomposition. Such places are known to farmers as "dead lots," because no stock will live on them. The bacillus in the buried carcase does not produce spores (Bollinger), though it may in the soil at any temperature between 59° and 110° F. In the graves, therefore, at a lower temperature, the poison can only be preserved by a continuous generation of the bacillus.

Pasteur, who successfully inoculated the casts of earth-worms taken from anthrax graves, attributes to these an important rôle in bringing the germs to the surface. A more important agent, however, is probably the rise and fall of water in the soil. By this means the bacilli and spores are washed up toward the surface, and when the superficial layers dry out they are easily carried by the winds. Hence it is that anthrax is usually prevalent in late summer and when the soil is dried and heated to its {931} greatest depth. Thus it is, too, that wet seasons followed by specially dry and hot ones are, above all, productive of anthrax in herds. Wet seasons fulfil the further purpose of carrying off the germs into rivers and depositing them on the banks or on inundated meadows, where after the subsidence of the flood the disease appears, for the first time perhaps.

There is, however, good reason to believe that the effect of a warm season is not confined to its influence on the soil and its germs. The high temperature deranges the vital functions of the animal economy, and, inducing a febrile disturbance, lessens the power of resistance to the anthrax virus, just as the cooling of the warm-blooded bird lays it open to infection. On this account, and because of the frequently recurring electric storms, the hot dry season is especially the season of anthrax. The hottest, driest autumns of Siberia always coincide with the anthrax years, and in the last fifteen years in the United States I have noticed the wide extension of anthrax whenever the season has been unusually hot and dry. In Corsica the herdsmen confidently pasture their stock in the close still valleys throughout spring and early summer, but whenever the surface soil is dried out they make all haste to remove it to the hills, well knowing that delay means devastation and ruin.

Plethora is undoubtedly an important predisposing cause of anthrax, and so is the alternation of cold nights with hot days. The febrile condition induced in the animal economy is perhaps the main factor at work in each case. Finally, youth is on the whole more liable than age, but whether because of the greater receptivity of the growing system and its tissues, or because it has not yet acquired some immunity by exposure to the milder effects of the poison, is not certainly determined. Sex is without influence.

It is not a little remarkable that the bacillus germ has not yet been found in the placental liquids nor foetal blood of sheep, goats, or rabbits, though swarming in that of the mother. Bollinger attributes this to the action of the placenta as a "physiological filter"--a conclusion seemingly at variance with the passage of the bacillus through all the other animal membranes, including those lining the mammary glands and the vagina. Two other possible explanations remain: first, that the secretions of the uterine glands are inimical to the bacillus; and, second, that the foetus, being in some sense a carnivorous animal, possesses the immunity characteristic of Carnivora. Bacilli have recently been found in the foetal guinea-pig.

The bacillus anthracis was first observed by Pollender and Branel in 1849 (Birch-Hirschfeld), but it was only publicly claimed as the cause of the disease in 1855 by Davaine. Branel discarded Davaine's theory, because blood in which he had failed to find bacillus produced anthrax with bacillus in the blood of two foals inoculated. Later observations by Bollinger and others have shown that cultures of bacillus can always be made from such infecting blood, and that in most cases the presence in the infecting blood of spherical bacteria can be demonstrated by the microscope. That the bacillus is the true pathogenic element is proved by the following facts: 1st. That the bacillus is the only ectogenous, particulate, organized structure constantly found in the anthrax blood and fluids; in cases in which it is apparently absent cultures show its actual presence. 2d. After cultivation in pork or beef infusion to the {932} hundredth generation the virulence is unimpaired, though it must be assumed that all non-organized poisons derived from the infected animal body must have been diluted or decomposed to extinction. 3d. That filtration of the anthrax liquids through a plaster or other efficient filter renders the filtrate innocuous, while the solids retained in the filter remain infecting (Chauveau, Bert, Toussaint). 4th. That the clear filtrate injected to excess killed by virtue of its contained chemical products in twelve hours, while the solids filtered out and containing the bacillus or its spores only killed after thirty hours. 5th. Anthrax blood from the living animal or one just dead, and destitute of spores, when subjected to compressed oxygen (50 atmospheres), is non-infecting (Bert). 6th. The same anthrax liquid, destitute of spores, after boiling is completely innocuous. 7th. The same liquid, if kept in a closed tube apart from oxygen for eight days, shows the bacilli broken down by granular degeneration, and proves absolutely harmless when inoculated in small quantity. 8th. The same sporeless anthrax fluid when treated with absolute alcohol loses its virulence. 9th. The anthrax liquid which has been cultivated with free access of air in a temperature varying from 25° C. (77° F.) (Klein, Löffler) to 41° C. (105.5° F.) forms spores, and then remains infecting, though it may have been subjected to compressed oxygen, boiling for several minutes, absolute alcohol, dilution with water, putrefaction, or the exclusion of oxygen.

The bacillus anthracis, as found in the blood and animal fluids, is in the form of fine rods, straight (rarely bent or angular), motionless, and 0.007 to 0.012 Mm. in length. Smaller forms are seen to be minute ovoid or oblong bodies, and the smallest absolutely spherical (micrococcus); but in all cases, as seen under the highest powers of the microscope, they have clear-cut, even margins, linear or curved, which easily distinguish them from the irregular normal granules of the blood and tissues. Under the highest powers of the microscope the bacillus is seen to be made up of a series of oblong (Koch) or cubical (Klein) cells enclosed in one common sheath. This is rendered more manifest if they are first swollen by the addition of water. The motionless form of the anthrax bacillus is of especial value in distinguishing it from the motile bacteria of putrefaction (saprophytes).

Within the living animal body the development never goes aside from these forms. The growth appears limited to micrococcus and bacillus rods, while spores or bacillus threads are never found. This finds its counterpart in the micrococcus poisoning caused by the inoculation with the spores of common moulds (Grawitz); and in septicæmia also micrococcus and bacillus forms only are found, the filamentous never.

When grown in organic infusions out of the animal body the anthrax-germ develops from micrococcus or bacillus into a long, branching, filamentous product, which in the presence of oxygen develops into spores. Apart from oxygen or when the proper nourishment of the bacillus is exhausted the protoplasmic elements within the filamentous sheath undergo granular degeneration, and finally the empty envelope disintegrates and disappears. The spores appear at intervals in the protoplasm of the filament as clear, brightly refrangent bodies, at first spheroidal, afterward larger and oblong. Unlike the micrococcus and bacillus, {933} they do not stain. Under favorable circumstances the primary cell is capable of forming one, or if extra long, two spores (Koch, Klein). Cossar-Ewart claims to have seen the formation of motile flagellate organisms aggregating themselves into zooglæa masses, but as these were not found in the carefully-conducted cultures of Koch and Klein, they are supposed to have been aërial microphytes accidentally introduced.

The great tenacity of life in the spores in heat and cold, dryness and wet, excluded from air and under several atmospheres of oxygen, in the midst of putrefaction and in pure watery fluids, well accounts for the persistence of infection in buildings and localities where the poison has gained a foothold. In order to their destruction in a natural manner it seems necessary that they should germinate and develop into the anthrax micrococcus, bacillus, or mycelium. This germination may take place in the presence of moisture, oxygen, and suitable nourishment, whether in the soil, the animal body, or elsewhere, and then the exhaustion of the aliment, the exclusion of the oxygen by putrefaction, the submergence in a medium unfavorable to development, or exposure to a very high temperature, may suddenly destroy the poison.

There is reason to believe that a too free exposure to oxygen proves destructive to the virulence, if not to the life, of the poison, and thus in all porous, well-drained soils the anthrax poison, even when introduced from without and concentrated by the death and burial of many victims, soon disappears. This feature, which is common to many zymotic diseases the germs of which live and multiply outside the animal body (typhoid, yellow fever, tuberculosis, swine plague, chicken cholera, diphtheria, etc.), offers countenance to the claims of Buchner that he had by prolonged culture, in the presence of air, metamorphosed the bacillus anthracis into a harmless mycrophyte, and that, conversely, by continuous cultivation under the surface of a suitable beef infusion he had changed the harmless bacillus subtilis of hay into the deadly bacillus anthracis. Koch, Klein, and others have discredited Buchner's results, on the ground that he had not, in their opinion, taken due precautions against impure cultures, and that his alleged transitions took place too abruptly; yet further observation must determine whether he has been condemned too hastily. The diminished virulence of Pasteur's attenuated virus, which is unaffected by the next subsequent culture or by the formation of spores, shows plainly enough that the bacillus anthracis is capable of physiological changes under the influence of varying conditions of growth, and that such changes are not at once undone by a return of the former conditions.

How anthrax-germs enter the body is partly known and partly conjectured. Direct inoculation on a sore by contact, by insects, by harness, by accidents, etc. is an undoubted method. The sound cuticle is probably an efficient barrier, since bacteria habitually inhabit, without hurt, the surface and gland-ducts of the skin; yet the entrance of these saprophytes through the shell and membranes of the egg leaves a doubt as to the efficiency of the cuticular obstacle. The mucous membranes are manifestly frequently penetrated by the parasite. Hence the local affections in the mouth and throat (glossanthrax, anthrax angina) and in the lungs (pulmonary anthrax). Cohn claims that the gastric juice of Carnivora especially is destructive to the anthrax poison, yet the constant recurrence of intestinal anthrax (mycosis) seems to imply that the germs often escape destruction {934} in the stomach. Pasteur supposes that anthrax-infected food is only injurious when there are inoculable sores in the mouth or pharynx, but it seems as if in that case the disease would be first shown at these points and in the nearest lymphatic glands rather than in the bowels, the rule for the inoculated anthrax being to develop first in the tissues and thence to reach the blood-vessels through the lymphatics.