SUPPRESSION AND PREVENTION OF ANTHRAX IN HERDS.
Less simple or easy than in plagues. Germ survives in soil and water. Extinction not always possible. Killing: conditions demanding it: when unwarranted. Kill without shedding blood, or opening carcass. Body burned: if buried, 5 feet deep, in porous soil, distant from wells, ponds, and rivers. Fence graves, burn grass. Disinfection of hides, litter, fodder, manure, excretions, stalls, etc.: of bodies that must be moved, of buildings, yards, utensils, etc. Isolation of unaffected on porous soil; surveillance. Sales interdicted. Milk, butter, cheese. Immunization: by toxins which stimulate leucocytes to form defensive products: antitoxins. Eosinophile cells, action of spleen, and liver. Mellituria. Protection by a minimum dose: by weakened virus—modes of lessening potency, Pasteur’s “vaccine”, its drawbacks and dangers, its technique; by soluble toxins in sterile solution, author’s experience, apparent failures, advantages. Drainage—Æration of land. Prevention of importation and diffusion. Therapeutic treatment.
Prevention of anthrax in animals is equally important for the sanitation of herds and human beings. It involves the purging from the anthrax bacillus of the infected lands and the drinking supplies, and in this respect the disease is much less amenable to thorough and speedy extinction than is a simple plague in which the germ does not live and multiply outside the animal body. In some localities the extinction of the germ may be confidently counted on and secured; in others, it may be impossible and other measures of protection must be resorted to.
Killing of the Sick and Disposal of the Carcass. This is not always so imperative as in the obligatory parasitic infections, since the destruction of the sick, still leaves the germ present in the soil and water. If, however, the infection has just been introduced, on hitherto uninfected soil, by the arrival of new animals, and, if the new location is in any way favorable to permanent colonization by anthrax bacillus, and, if the diseased and suspected animals cannot be kept secluded so as to absolutely exclude these dangers, or again, if the diseased herd or its remnant is to be moved on to another locality, slaughter is the obvious sanitary measure.
The animal should be killed on the premises to avoid the danger of scattering the infectious discharges in transit; it must not be bled, nor cut open, as the admission of air determines the formation of the resistant spore; and the carcass must be burned, boiled, or rendered in superheated steam under pressure, or finally dissolved in strong mineral acids. If buried, it must be in open, porous soil, well apart from any well, pond, river, or bank where the liquids may leach out, and the body must be wholly covered to a depth of at least five feet. The graves must be well fenced in from all stock, for a number of years, and no forage grown on them can be safely fed to animals, as the bacillus can be brought to the surface by earth worms. I have known cattle to become infected through licking the fluid which escaped above a stratum of clay, on the deep bank of a river, at some little distance from where an anthrax carcass was buried in the surface sandy loam. A covering of coal tar, chloride of lime or of sand charged with sulphuric acid is an admirable precaution.
As a measure of economy the skins may be removed, if at once, on the spot, plunged for 12 hours in a 5 per cent. solution of carbolic acid, or cresyl, or creolin, or in a two per cent. solution of sulphuric acid, and, if the knives and other implements used are placed in boiling water for half an hour. The same will apply to fleeces.
Disinfection. All litter, fodder, manure, urine, and other excretions, or products; all stalls, feeding troughs, sheepfolds, covers, halters, harness, wagons, poles, shafts, and other objects used about the animals, or soiled by them or their products, should be disinfected by burning, flaming or scalding (boiling), when applicable, by one of the above-named disinfectants, by mercuric chloride (5:1000), by formalin, or other potent antiseptic. Extensive dung heaps, too wet to burn, may be sprinkled freely with strong mineral acids, or mercuric chloride in solution, piled into compact mass, covered with chloride of lime, and finally with a thick layer of earth, and fenced in from all stock.
If carcasses must be moved to the grave, rendering works, or elsewhere, they should be sponged with carbolic acid solution, formalin, or mercuric chloride, and each of the natural openings firmly plugged with tow or cotton soaked in the same material, so that no infecting material may drop on the way. They should on no account be dragged on the ground, but carried on a wagon or stone boat, which should be afterward carefully disinfected. Men or animals, entering an infected place, should be disinfected on leaving; especially hands and feet.
All roads, yards, and pastures where the sick have been, and, above all, where manure, urine, or saliva has fallen, should be subjected to thorough disinfection, or the surface layer removed and deeply buried. Where available, a concrete or asphalt floor should be placed in the buildings.
Isolation. Movement from Infected Ground. It has long been known that the movement of an infected herd from the contaminated pasture to another, will often, at once, check the development of new cases. In Sardinia and Auvergne the flocks and herds were yearly moved on the approach of autumn, from the rich valley, and bottom lands, to the drier hill pastures, to avoid or lessen the decimation that otherwise inevitably overtook them. This is in keeping with the enzoötic nature of the malady which arises more from the microbe preserved in the soil than from the sick animal direct. Two precautions are necessary in making such a change of locality: 1st, Animals already infected should not be moved on such new pasture; and 2d, the pasture to which the stock is moved should be entirely free from the impermeability (clays, hard pans), and saturation with water (swamps, basins, low bottoms), which would ensure the permanent preservation of any microbe planted there. Elevated, sandy, argilaceous or loamy soils are to be selected. To these the animals of the infected herd which by their appearance and thermometry may be pronounced sound, should be removed, and kept under careful supervision, especially as regards thermometric tests. Any showing symptoms of anthrax should be at once taken back to the infected herd. If they have stood in stalls, for milking or otherwise, these should be disinfected, and they should be carried in wagons, or driven by unfrequented roads. Their droppings should be carefully disinfected.
If, in the absence of anthrax symptoms, animals must be kept in the infected lot, or returned to it, they should be immunized.
Interdiction of Sales. No animal in the infected herd which shows a rise of temperature, should be sold even for slaughter. No animal should be sold for stock purposes until the disease has completely subsided. Any animal in the infected herd, which shows no hyperthermia nor other sign of anthrax, may be sold for immediate slaughter, subject to a critical expert examination of the cadaver for anthrax. Milk, the product of an infected herd, and butter and cheese made from such milk, should not be used as food. If those members of the herd, that show no hyperthermia or other symptom of anthrax, can be held apart as a separate herd, in a disinfected place and under careful thermometric observation, their dairy products may be used.
Immunization. A number of different methods have been practiced of rendering animals refractory to the bacillus anthracis, but all are apparently based on the production in the system of defensive products, as the result of a nonlethal poisoning with anthrax toxins. It is true of anthrax as of many other infections that a first attack protects against a second. In all animals there is a certain measure of defensive power against the bacillus anthracis, amounting in some cases to virtual immunity and in others having a very little effect. The object in immunizing is to stimulate to the increase of these defensive products in quantity or power until an ordinary dose of the bacillus will fail to colonize the tissues or the blood. In considering this subject a clear distinction must be made between the simple bactericidal and the antidotal or antitoxic products found in the serum of immune animals and the toxins which are produced by the bacilli. The soluble antitoxic and bactericidal agents found in the serum of the immune, may be employed for therapeutic purposes to preserve life in an animal which has received a lethal dose of the bacillus anthracis, but as these are rapidly eliminated from the system, their protective power is very short lived, and if some bacilli survive the period of their presence and potency, or if they are introduced into the system later, the animal may fall a victim to anthrax as if no such protective agent had been used. Behring showed that the blood serum of the white rat proves fatal to the bacillus anthracis, but Metchinkoff pointed out later that it must be brought in contact with the bacillus in order to prove effective, whereas if the serum and bacillus were injected at different parts of the body no protection was obtained. The antidotal or bactericidal action of the serum of an immunized animal acts at once, whereas a permanent immunity cannot be established before about fifteen days. The serum of the immune animal contains the following elements antagonistic to anthrax: Antitoxin or leucomain which may be poisonous to the bacilli, or chemical antidotes to their products: globulicidal principles which distort or disintegrate the blood globules and release their contents including the bactericidal nuclein, and probably others. All such agents when injected into the system are present only for a limited time and while they may be made subservient to a temporary immunity, they can give no permanent protection and must be considered mainly as therapeutic agents.
A permanent immunity must depend on a stimulation or education of the system to the production of these protective agents de novo or in increased quantity. This must be done by exposure of the tissues to the toxins of the bacillus anthracis, and is accomplished slowly. Precisely what tissues are stimulated to the production of the defensive agents is not fully known, though certain indications may be drawn from observant facts. The eosinophile cells of the blood are presumably important factors as the natural sources of the leucomaines. The spleen as the seat of important blood changes and as preëminently the seat of election of internal anthrax is probably involved. The dogs from which Bardach had removed the spleen were found to be three times as susceptible to anthrax as were the dogs that had not been operated on. Leo’s rats, in which he had produced mellituria by the administration of phloridzin were found to be much more susceptible to anthrax. The liver is also a favorite seat of election of internal anthrax. The products of the healthy liver, are probably in some measure protective.
No matter where the defensive products are formed, the practical problem is to secure their production without imperilling life.
By Minimum Dose. Chauveau and Colin secured this in the larger animals by intravenous injection of a minimum dose,—one or two bacilli. This is more lasting in effect if a second and stronger dose is injected some days later.
By Weakened Virus. This has been secured by heating the defibrinated blood to 55° C. for ten minutes (Toussaint); Pasteur, Chamberland and Roux accomplished the same end by making anthrax cultures at 42° to 43° C. in presence of air; Chauveau by subjecting the virulent culture for eight days to oxygen under a pressure of 8 atmospheres at a temperature of 38° C.; Chamberland, Roux and others have cultivated the bacillus in weak antiseptic bouillons as phenic acid (1:600 or 1200), bichromate of potash (1:2000 or 5000), sulphuric acid (2:100).
Other methods have been followed, as growing the bacillus in the blood or serum of immune animals (dog, chicken, pigeon, white rat, frog).
Of these different methods that of Pasteur has been most extensively adopted. The temperature of culture (42° C.) prevents the formation of spores and the duration of exposure to air gradually lessens the virulence until in 12 or 13 days it is not fatal to the Guinea pig and after 31 days it fails to kill the young mouse. Thus preparations of varying grades of virulence, and adapted to the varying susceptibility of different animals, are secured. The protective inoculation is made by preference in spring, when there is less chance of complication by a coincident accidental infection, it is to be avoided if possible in animals at hard work, in advanced gestation, in full milk, in extreme youth, or in ill health. To secure the best results it should be repeated with a stronger preparation 12 to 15 days after the first injection. The acquired immunity lasts a year and over, and it is probably perpetuated by new and non-fatal doses taken in casually, on the anthrax pastures. Hundreds of thousands of live stock in all parts of the world have been treated in this way with the result of reducing a mortality of two, five or ten per cent. to insignificant proportions. It can only be safely adopted on anthrax lands, as elsewhere it may lead to the stocking of new areas with a malignant germ which in young and susceptible animals reacquires its original virulence.
It can never be safely ignored that we are dealing with the living seed of a most deadly infection. Though robbed of a large part of its virulence by artificial culture at 107:5° F., yet many accidental conditions, contribute to a relapse to its original potency, and when it has once killed a victim, the reacquired virulence is usually persistent. If the virus employed for protective purposes in cattle and sheep, is inoculated on Guinea pigs of 1 to 30 days old, from these on those of several months, and from these last on sheep, the virulence is constantly and persistently enhanced. The same is true of the microbe which is inoculated on a succession of pullets of steadily encreasing ages (Roux and Chamberland), or on a succession of pigeons (Metchnikoff). The germs reinforced in potency in any such way are liable to be the starting points for dangerous infections in animals and permanent contamination of soils and waters. Fortunately an occurrence of this kind is rare, yet with a wide application of the Pasteurian inoculation the opportunities also are great, and with the free sale and distribution of the mitigated virus (anthrax “vaccine”), the evil may grow indefinitely. The method departs from the ideal one, aimed at a final extinction of the disease, and accepts in place a mere temporary protection of the herd or flock, and though in this affection eradication cannot always be secured, every effort should be made to gain it and above all to prevent an encrease of the area of infection.
Technique. The weakened virus (1st “vaccin”) is sold in tubes holding enough for 100, 200, or 300 sheep. Of this ⅛ cc. is injected subcutem on the inner side of the thigh of the mature sheep, and 12 or 15 days later a similar dose of the stronger preparation (“2d vaccin”). For the ox or horse double the amount (¼th cc.) is used, being injected behind the shoulder, and on the side of the neck in the respective animals. The dose is graduated in the different subjects according to the size and age, yet a considerable latitude is permissible. The syringe must be disinfected before and after inoculations by a 5 per cent. solution of carbolic acid, or by boiling, and the nozzle should be dipped in strong carbolic acid immediately before and after each insertion. This will greatly obviate infection of the liquid used, and of the wound by any virulent germs lodged on the surface of the skin. The liquid to be injected should be used as soon as possible after preparation, and if kept should be in a dark cold place, and if the tube is once opened the whole of its contents should be used the same day,—never kept over. The second, stronger preparation should never be used until the system has been prepared for it by the use of the first.
By the Soluble Toxins in Sterile Solution. In 1884, in an outbreak of anthrax in Skaneateles, N. Y., I drew blood from an anthrax cow, subjected it to 212° F. for 30 minutes, dissolved out the soluble toxins in boiled water, and injected the product subcutem, in the dose of 2 to 4cc. according to size, into every apparently healthy member of the herd, excepting one, which was left as a check. The check animal died of anthrax while all of the others escaped.
Since that time I have personally used it in every herd where opportunity offered, and with equally good results. In an outbreak near Elmira, Dr. Moore adopted it in a large dairy herd, and the disease was suddenly arrested.
In several experimental cases (one cow and 2 Guinea pigs) at the N. Y. S. V. College, the outcome was not so satisfactory and in a herd in Oneida Co., N. Y., it is said to have failed to check the disease.
Notwithstanding these untoward results in other hands, I am still confident that we have in this a measure of no small value, and worthy of application in suitable cases. A certain percentage of failures in immunization are to be looked for. Even cowpox vaccination is not always protective against itself; I knew one man who was successfully vaccinated every three years in a comparatively long series. Many habitually self-limiting diseases relapse in particular individuals. Even in the case of anthrax excess of glucose in the system, and the lack of some unknown influence of the spleen are respectively destructive of immunity. Even after the Pasteurian inoculation a certain number of inoculated animals are lost, it may be between the first and second injection, or it may be “two or three months” after the latter (Galtier). We must also bear in mind that in an infected herd or flock, there are always a certain number already infected at the time of the protective inoculation, and as the protective conditions are slowly established, through the action of the leucocytes, it is unreasonable to expect that serious illness and death can be obviated in such animals.
In inoculation with the Pasteur lymph, the bacillus is held not to enter the blood, a position supported by the researches of Bitter, Perroncito, Wissokovicz, Lubarsch, Metchnikoff, Chamberland and Roux, so that the resulting immunization must come from the toxins. Add to this that Chauveau (1885), conferred immunity on a sheep by injecting intravenously, anthrax blood, defibrinated and sterilized by heat: Arloing obtained immunity in the sheep by injecting, subcutem, the clear supernatant liquid from old bouillon cultures of anthrax, from which all bacilli had been precipitated. Roux and Chamberland obtained the same result by using the pulp of an anthrax spleen treated with essential oil of mustard, so as to destroy the life of the bacillus, and then evaporated in vacuo to remove the essence. Smaller doses proved effective, than when the splenic pulp had been filtered or sterilized by heating to 58° C.
The advantages of using sterilized toxins are numerous:—
1st. As the material can be derived from a case of the outbreak in hand, there is no risk of using the anthrax protective inoculation for black quarter, hæmorrhagic septicæmia or other disease which is so often confounded with it.
2d. There is no danger of the sudden enhancing of the potency of a weakened microbe on account of some condition of the animal inoculated, as no living microbe is employed.
3d. There is no possibility of planting the anthrax bacillus, on new soil, as is so liable to take place in using the weakened microbe.
4th. There is no necessity for the care and cost of holding the inoculated animals apart by themselves, under official veterinary control for 15 days, of withholding their products from market, or of disinfecting the place where they have been kept. On the contrary the animals inoculated can be treated in every way as if no such injection had been made.
Thorough Drainage and Æration of Land. The most thorough and permanent method of eradicating anthrax is by thorough æration of the soil. In dry, sandy, or gravelly soils, having a good natural or artificial drainage, and not underlaid by an impermeable damp stratum, the bacillus is never permanently found, and, if introduced, is slowly robbed of its virulence by the action of the oxygen. When a soil can be well and permanently ærated by thorough underdrainage, a few years suffice to rob it of its infecting property and render it salubrious. In many localities, however, this is actually or economically impossible, so that the owner is thrown back on the alternatives, of abandoning the soil for stock, or of immunizing all the animals placed on it.
Prevention of Importation of Anthrax. To prevent the introduction of anthrax into a country or district, the usual control must be exerted on trade in cattle and their products, as in the case of other infectious diseases. The exclusion of livestock from an anthrax-infected country or district, or the admission after 6 to 10 days of quarantine and the disinfection of the surface of the animal. Dried hides, horns, hoofs, hair, wool and bristles are even more dangerous, as they are liable to hold the microbe in the spore form which will survive indefinitely and plant the disease widely. The recent great extension of the disease along the Delaware River, in connection with the morocco factories, which draw their hides from the most virulently anthrax regions (India, China, Russia, Africa, S. America) is a strong case in point, and nearly every tannery planted on a favorable soil is an example on a smaller scale. Disinfection of all such products on arrival is essential. But this should be thorough, and no question of trouble nor expense should stand in the way. If the trade cannot stand the expense, it has no right to exist where it is, at the expense of threatened ruin, local and ultimately general, of agriculture, on which all other industries are based. Similar control is demanded of live stock products from infected regions in America.
The control of home markets, stockyards, and abattoirs is no less important. Fortunately the disease is shortlived and deadly, and is much more easily discovered and arrested than in the case of plagues with prolonged incubation and frequently occult form (glanders, tuberculosis). An inspection of the various markets, and the detention of herds that have shown anthrax infection would do much to limit extension. This would entail the disinfection of the infected places, cars, boats, harness, clothing, and other things, and of the skins of the healthy animals of the infected herd.
The Therapeutic Treatment of anthrax in animals must in the main follow in the same lines given below for the human being; locally, antiseptics (mercuric chloride or iodide, Luzol’s solution, hydrochloric acid, phenic acid, iodized phenol, creoline, cresyl, oil of turpentine, formalin, salicylic acid, scarification, excision of the primary sore or swelling with antisepsis, antiseptic injections into the swelling.) Internally, there have been employed, dilute phenic acid, creolin, terebene, calomel, quinine, hydrochloric acid, bichromate of potash, tincture of iron chloride, etc. (see below).