Part 77

(1) Slaked lime is perhaps the most easily procured, but its disinfecting power is limited. While it is capable of destroying all bacteria in their vegetative state, it is unable to destroy such spores as those of anthrax and blackleg. It is probable, however, that in incrusting spores it may destroy their vitality sooner or later. It is regarded as safe practice to use only spore-destroying substances for the virus of those diseases of which we have no definite knowledge. Nevertheless, in the absence of other disinfectants, lime is very useful. It may be employed as a whitewash on wood and stone and sprinkled as a dilute wash or in powder over yards, manure heaps, and over carcasses before they are buried, and over the ground on which they have lain to prevent other animals from carrying the infection away.

(2) Chlorid of lime is more efficient than simple slaked or unslaked lime, as it destroys spores. It is the ordinary bleaching powder of commerce and is quite unstable, hence old preparations, unless sealed, are of little value. A 5 per cent solution is sufficiently strong for all spore-bearing bacteria (3 ounces in 2 quarts of water). It may be efficiently applied to the walls and floor of an infected stable by mixing with limewash in the proportion of 6 ounces of the lime to each gallon of limewash. The ceilings and those portions of the walls which can not be reached should be disinfected by means of chlorin gas liberated from the chlorid of lime by crude carbolic acid. This is accomplished by making a cone of 5 or 6 pounds of chlorid of lime, in the top of which a deep crater is made for the placement of from 1 to 2 pints of crude acid. The edge of the crater is thereupon pushed into the fluid, when a lively reaction follows. The fumes of chlorin are strongly irritating to the respiratory tract and therefore all live stock should be removed before the work is started. Owing to the heat generated, it is advisable to place the lime in an iron crucible and to have nothing inflammable within a radius of 2 feet. The number and location of these cones of chlorid of lime depend on the size and structure of the building to be disinfected. As a rule, it may be stated that chlorin gas liberated from the above-sized cone will be sufficient for disinfecting 5,200 cubic feet of air space.

(3) Crude carbolic acid. The ordinary purified carbolic acid is too expensive to be used on a large scale, and the crude produce is a very good substitute. This is made more powerful by mixing with it an equal volume of commercial sulphuric acid. While the sulphuric acid is being added to the crude carbolic acid much heat is evolved, and if the glass jar in which the two are mixed is placed in cold water the resulting product is said to have a higher disinfecting power. The mixture is added to water enough to make a 5 per cent solution (about 7 ounces to 4 quarts of water). This is strong enough for all purposes. It may be kept in wood or glass, but not in metal, owing to the corroding action of the acid. It should be used freely on woodwork and on infected floors, and a force pump of the kind used by orchardists is very convenient as a means of applying the disinfectant. If the solution is warm when applied, it will penetrate the woodwork better than when cold, especially if the spraying is done during cold weather. The addition of air-slaked lime in any quantity that will dissolve in water to the above solution (say 1-1/2 pounds of lime to 7 ounces of crude carbolic acid to each gallon of water) is preferred by many, as it makes any neglected places at once visible and leaves cleaner and better air within the buildings. In most cases in which its application becomes desirable--and this rule should apply to all disinfections--the disinfected stables, stalls, etc., should remain vacant as long as possible before cattle are again stabled therein.

(4) Mercuric chlorid, or corrosive sublimate, is a powerful disinfectant, but it is likewise very poisonous; hence its uses are limited. Cattle are especially susceptible to its action and caution must be used in its application. A solution of one-tenth of 1 per cent is usually sufficient (1 ounce to 8 gallons of water). It should not be placed in wooden pails, which would form the tannate of mercury, a weak antiseptic; nor, owing to its corrosive action, should expensive metal pails be used. Agate vessels or tin pails are to be preferred. All solutions should be labeled "poison," and to avoid accidents none should be kept on hand.

(5) Formalin and formaldehyde gas have been found very efficacious as sanitary agents. Formalin is the commercial name for the 40 per cent solution of formaldehyde gas in water, and is one of the most powerful antiseptic and disinfectants that we possess. Solutions of this strength are manufactured by different commercial houses and sold by the drug trade under the name of "formalose" and "formal." In this connection it should be mentioned that while the 40 per cent solution of formaldehyde gas and formalin are exactly the same thing, the former can be purchased at 33-1/3 to 64 per cent less than the latter. Formalin, diluted with water in the proportion of 1 pint to 30 parts of water, or 4 ounces to each gallon of water, may be applied, and it may thus be used as a wash or as a spray on all paints, metals, and woodwork, as well as on clothing and other fabrics, without injuring them. It may also be applied to floors, walls, and woodwork in whitewash by mixing 1 part to 30 parts of limewash, or 4 ounces to each gallon of limewash. Formalin has the appearance of water and in the strong solution is poisonous, but when diluted as recommended above it is not dangerous. The fumes given off by it, however, are very disagreeable and irritating to the eyes and nasal mucous membranes. One and one-half ounces of formalin added to 1 gallon of water is a valuable agent for the disinfection of the skin or septic wounds, but is somewhat painful and irritating to raw surfaces.

Formaldehyde is a gas which is soluble in 2-1/2 parts of water (40 parts of formaldehyde gas to 100 parts of water); this solution constitutes the formalin of commerce. The use of formaldehyde gas is in most cases impracticable for stable disinfection. In case the stable is not too large and can be made almost air-tight the generation of formaldehyde gas, after removing all the animals, will be found very serviceable. It penetrates all parts of the stable--the walls, crevices, floors, ceiling--and is probably the best fumigating disinfectant that we have.

Probably one of the most simple and practical methods of liberating this gas is by means of the chemical reaction which takes place when formalin is poured upon permanganate of potassium. For each 1,000 cubic feet of air space, 16-2/3 ounces of crystallized or powdered permanganate of potassium is placed in a wide-surfaced pan; 20 ounces of formalin is then poured upon it, and the stable immediately closed for a period of 12 hours or longer. This method is efficient only when it is possible to seal tightly the place to be disinfected, and should be used only by experienced persons.

(6) Some coal-tar products are cheap, effective, and easily applied disinfectants, their action being due to the carbolic acid and creosote in their composition. They may be used in 3 to 5 per cent solution. As a rule they form a milky solution in water.

(7) Compound solution of cresol (liquor cresolis compositus), now recognized as an official preparation, is composed of equal parts of cresol and linseed-oil-potash soap. The mixture is a thick, dark, amber-colored fluid which mixes readily with water in all proportions to form a clear, soap solution. It is an efficient disinfectant in a 3 or 4 per cent solution, and in this strength it may be applied in the same manner as a 5 per cent solution of carbolic acid.

When it is desired to apply one of these above-mentioned agents to the stable or barnyard, a preliminary cleaning up of all dÈbris and litter is advisable, together with the scraping of the floor, mangers, and walls of the stable with hoes; also the removal of all dust and filth. This should be followed by the burning of all such accumulations, inasmuch as this material likewise contains the infectious principle and is best destroyed by heat. Heat may be applied to the surface of the affected pen, byre, or barnyard by means of a cyclone burner, which consists of a tank, pump, hose, and cyclone nozzle for spraying with paraffin (gas oil). The latter is ejected in the form of spray, which when ignited gives a very hot and effective flame to be applied to the infected ground. Where such burning is impracticable the surface soil of the yard and surroundings should be removed to a depth of 5 or 6 inches and then placed in a heap and thoroughly mixed with air-slaked lime. The fresh surface of the soil thus exposed may then be sprinkled with the disinfectant.

In addition to these artificial substances there are several natural sanitary agents of great importance as destroyers of virus. These are cleanliness, ventilation, drying, and sunshine. All virus, excepting such as may live in the soil, is killed sooner or later by drying and sunshine, and the importance of these factors in the daily life of animals need not be insisted on here. Finally, all sanitary measures which contribute to the healthfulness of animal surroundings are directly or indirectly inimical to disease germs, and all carelessness in the keeping of animals may be regarded as an ally of these destructive organisms.

CONTAGIOUS PLEUROPNEUMONIA.

Definition and history.--This disease has been eradicated from the United States, and it is not probable that it will ever be seen in this country again. As, however, much interest was manifested in regard to it for a number of years, and as our cattle are still prohibited from some foreign markets on account of its previous existence here, the subject is treated at greater length than would otherwise be necessary.

The contagious pleuropneumonia of cattle is a specific, epizootic disease which affects bovine animals, and from which other species are exempt. It is characterized, when the disease results from exposure in the usual manner, by an inflammation of the lungs and pleurÊ, which is generally extensive, and which has a tendency to invade portions of these organs not primarily affected and to cause death of the diseased portion of the lung. This disease is frequently called the lung plague, which corresponds to its German name of Lungenseuche. In French it is spoken of as the pÈripneumonie contagieuse.

The history of the contagious pleuropneumonia of cattle can not be traced with any certainty to a period earlier than the beginning of the eighteenth century. No doubt it existed and ravaged the herds of Europe for many years and perhaps centuries before that time, but veterinary knowledge was so limited that the descriptions of the symptoms and post-mortem appearance are too vague and too limited to admit of the identification of the maladies to which they refer. It has been supposed by some writers that certain passages in the writings of Aristotle, Livy, and Virgil show the existence of pleuropneumonia at the time that their works were composed, but their references are too indefinite to be seriously accepted as indicating this rather than some other disease.

It seems quite plain that as early as 1713 and 1714 pleuropneumonia existed in Swabia and several Cantons of Switzerland. There are even clearer accounts of its prevalence in Switzerland in 1732, 1743, and 1765. In 1769 a disease called murie was investigated in Franche-ComtÈ by Bourgelat which undoubtedly was identical with the pleuropneumonia of to-day. From that period we have frequent and well-authenticated accounts of its existence in various parts of Europe. During the period from 1790 to 1812 it was spread throughout a large portion of the Continent of Europe by the cattle driven for the subsistence of the armies, which marched and countermarched in all directions. It was generally prevalent in Italy in 1800. It appears to have been unknown, however, in the Department of the Nord, France, until 1826, but during the years from 1820 to 1840 it penetrated into most parts of that country. During the same period it was introduced into and allowed to spread over Belgium and Holland.

This contagion is said to have been carried to Ireland from Holland in 1839, and is reported as existing in England in 1842. The disease was brought to the United States at several different times. Probably its first introduction was with a diseased cow sold in Brooklyn, N. Y., in 1843. It came to New Jersey by importing affected animals in 1847. Massachusetts was infected in the same way in 1859.

South Africa was infected by a bull brought from Holland in 1854, and Australia likewise received the contagion with an English cow in 1858. It is also reported as existing in various parts of the Continent of Asia, but the time of its first appearance and the extent of its distribution are very uncertain.

Some countries, such as Norway, Sweden, and Denmark, which had been infected for only a short time, have succeeded in eradicating the disease without much difficulty by slaughtering all affected and exposed animals. Other countries long infected and in which the contagion was thoroughly established, like Australia, South Africa, Italy, France, Belgium, and parts of Germany, have labored long, in some cases making no progress and in others being only partially successful. Holland was one of the first of the thoroughly infected countries to free itself from the contagion.

In the United States, Massachusetts eradicated pleuropneumonia during the period from 1860 to 1866. New York and New Jersey made an attempt to eradicate it in 1879, but were not successful. Late in 1883 the contagion was carried to Ohio, probably by Jersey cattle purchased in the vicinity of Baltimore, Md., to which place it had extended before 1868. From the herd then infected it was spread by the sale of cattle during 1884 to a limited number of herds in Illinois, to one herd in Missouri, and to two in Kentucky. The alarm caused among the stock owners of the United States by this widespread dissemination of a disease so much dreaded led to the adoption of active measures for its control and eradication. By cooperation between the United States Department of Agriculture and the authorities of the affected States it was found possible to prevent the further spread of the contagion and to eradicate it after a few months' delay.

In 1886 pleuropneumonia was discovered in some of the large distillery stables of Chicago and among cows on neighboring lots. This led to renewed efforts for the complete extirpation of this disease from the country. Congress in 1887 enlarged the appropriation available for this purpose and gave more extended authority. During the same year the disease was stamped out of Chicago, and has not since appeared in any district west of the Allegheny Mountains.

The work of eradication was at the same time commenced in all the infected States. Before the end of the year 1889 Pennsylvania, Delaware, Maryland, the District of Columbia, and Virginia had been freed from the disease. More difficulties, however, were encountered in the States of New York and New Jersey, on account of the larger territory infected and the density of the population. The long struggle was successful, however, and the last animal in which the disease appeared in the State of New York was slaughtered early in 1891, and the last one affected in New Jersey met the same fate early in the spring of 1892.

During these same years a supreme effort had been made to stamp out this lung plague from Great Britain. From the official reports it appears that the number of infected districts and of diseased animals had rapidly diminished, but it was not until 1898 that the infection was finally eradicated.

The other infected European countries, though they maintain a veterinary sanitary service, are not making satisfactory progress in eradicating the disease. This is owing partly to delays in carrying out the provisions of the laws and partly to mistaken ideas as to the measures which are necessary to accomplish the object. The United States was the last of the countries having old infected districts which undertook to stamp out this contagion, and, except Holland, it was the first to reach success.

The cause (etiology) of pleuropneumonia.--This is a contagious disease, and arises only by contagion from a previously affected animal; consequently it can never be seen here except as the result of importing affected animals from the Old World. When thoroughly stamped out it does not reappear; and if imported animals continue to be properly inspected and quarantined, we have every reason to believe that pleuropneumonia will never again be seen in this country.

The exact nature of the virus or contagion of lung plague has never been determined. Various investigators have from time to time claimed the discovery of the specific organism of the disease, but it was not until 1898 that Nocard and Roux, by an ingenious method of cultivation, succeeded in obtaining a very feeble growth of an exceedingly minute microorganism. With these cultures the disease was produced in cattle.

Some investigators and writers are of the opinion that the disease can be contracted only by an animal coming near enough to a living diseased one to receive the contagion directly from it. They hold that the contagion is expired with the air from the affected lungs, and that it must be almost immediately inspired by another animal in order to produce the disease. Some experimental attempts to infect animals by placing them in stables where diseased animals have been, and by placing the diseased lungs of slaughtered animals in their feeding troughs have failed, and, consequently, apparently confirm this view.

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