Special Report on Diseases of Cattle Part 51

Other kinds of lung disease, because of certain features common to most lung diseases of cattle, may be confounded with pleuropneumonia. The inflammation of the connective tissue between the lobules is not infrequently observed in so-called interst.i.tial pneumonia and may lead to the formation of whitish bands intersecting the lung tissues in various directions. On the cut surface these bands may give rise to a decidedly marbled appearance. Again, in traumatic pneumonia, caused, as its name implies, by the entrance of foreign bodies into the lung tissue, generally from the paunch, the connective tissue around the place of disease becomes inflamed and thickened, and the disease itself may simulate pleuropneumonia in its retrogressive stages when it is confined to a small portion of lung tissue. The filling up of the interlobular s.p.a.ces with fibrin and connective tissue of inflammatory origin is not thus limited to pleuropneumonia, but may appear in a marked degree in other lung diseases.

It must not be inferred from this statement that these interlobular changes are necessarily the same as those in pleuropneumonia, although to the naked eye they may appear the same. We simply note their presence without discussing their nature.

In general, the distinction between pleuropneumonia and bronchopneumonia is not difficult to make. In the latter disease the pneumonia generally invades certain lobes. The disease attacks the smaller lobes in their lowest portions first and gradually extends upward, i. e., toward the root of the lung or the back of the animal and backward into the large princ.i.p.al lobes. Again, both lungs in advanced cases are often symmetrically affected. In contagious pleuropneumonia the large princ.i.p.al lobe of one side is most frequently affected, and a symmetrical disease of both lungs is very rare, if, in fact, it has ever been observed. The lung tissue in bronchopneumonia is not enlarged, but rather more contracted than the normal tissue around it. This is well ill.u.s.trated in Plate x.x.x. Normal, air-containing lobules may be scattered among and around the hepatized portion in an irregular manner. In pleuropneumonia the diseased and healthy portions are either sharply divided off, one from the other, or else they shade into each other by intermediate stages.

The hepatized lung tissue in bronchopneumonia when the cut surface is examined is visually of a more or less dark flesh color with paler grayish-yellow dots regularly interspersed, giving it a peculiar, mottled appearance. In the more advanced stages it becomes more firm, and may contain nodular and firmer ma.s.ses disseminated through it. The air tubes usually contain more or less soft, creamy, or cheesy pus or a turbid fluid quite different from the loose, fibrinous casts of acute pleuropneumonia.

The interlobular tissue may or may not be affected. It sometimes contains loose, fibrinous plugs, or it may be greatly distended with air, especially in the still normal portions of the lung. The pleura is seldom seriously diseased. If we contrast with these features the firm dark-red hepatizations, the plugging of the veins, the extensive interlobular deposits, and the well-marked pleuritis in pleuropneumonia, there is little chance for confusion between well-developed cases of these two lung diseases.

It should not be forgotten, however, that the lesions of the disease known as contagious pleuropneumonia may be confined to the serous membranes of the thorax, or they may be confined to the parenchyma of the lungs; they may affect a whole lobe, or only a small portion of it; they may or may not cause the so-called marbled appearance. In the same way bronchopneumonia may vary as to the parts of the lung affected, the extent of the lesions, the degree and kind of pathological changes in the interlobular tissue, the color of the lung on cross section and the amount of hepatization. In individual cases, therefore, it is often necessary to take into account the history of the animal, the course of the disease, and the communicability of the affection before a diagnosis can be made between the two diseases.

_Prevention and treatment._--The prevention of pleuropneumonia, as of other contagious diseases, consists in keeping animals so that they will not be exposed to the contagion. As the disease arises only by contagion, there is no possibility of an animal becoming affected with it unless it has been exposed. If, therefore, pleuropneumonia exists in a locality the owner of healthy cattle should make every effort to keep his animals from coming near affected ones or which have been exposed. He should be equally particular not to allow persons who have been on the infected premises to visit his own pastures, stables, or cattle.

If pleuropneumonia breaks out in a herd, every animal in it should be slaughtered, the stables thoroughly cleaned and disinfected, and no other cattle allowed on the premises until a period of 90 days has elapsed.

Medical treatment of affected animals is unavailing and should not be attempted. No matter how valuable the diseased animals may have been before they contracted the disease, they should at once be destroyed and the contagion eradicated. This is the best policy for the individual as well as for the community.

The eradication of this disease by local or National Governments can be successful only when the same principles are adopted and carried out as here recommended for individual stables. It is then a difficult undertaking, simply because the contagion is generally widely disseminated before any measures are adopted, and because a great majority of cattle owners will never report the existence of the disease. Regulations must therefore be enforced which will insure the prompt discovery of every herd in which the disease appears, as well as the destruction of all diseased and exposed animals and the thorough disinfection of the premises.

To discover pleuropneumonia sufficiently early for this purpose, the district supposed to be infected should be clearly defined and inspectors should be constantly employed to inspect every herd in it at least once in two weeks, or, better, once a week. No bovine animal should be allowed to go out of the defined district alive, and all which enter it should be carefully inspected to insure their freedom from disease. As an a.s.sistance to the discovery of diseased herds, every animal which, from any cause, dies in the infected district and every animal which is slaughtered, even if apparently in good health, should be the subject of a careful post-mortem examination. Many affected herds will be found in this way.

In addition to these measures it is also necessary to guard against the removal of animals from one stable to another and the mixing of herds upon common pastures or in the public highways. The object must be to isolate every individual's cattle as completely as possible, or otherwise a single affected animal may infect a dozen or more herds. To prevent surrept.i.tious sale or trading of cattle, each animal must in some way be numbered and recorded in the books kept by the official in charge of the district. In the work of the United States Department of Agriculture a numbered metal tag was fastened to each animal's ear and index books were so arranged that with a number given the owner could be at once ascertained, or from the owner's name the cattle for which he was responsible could be at once learned. In this way, if an animal was missing from a stable, the fact became apparent at once, or if one too many was found in a stable the number in its ear would indicate where it came from.

When pleuropneumonia is discovered by these means, the entire herd should be slaughtered as soon as the formalities of apprais.e.m.e.nt can be arranged.

In country districts the carca.s.ses should be buried, as it is generally impracticable to dispose of them in any other way. In city districts the animals may be taken to a slaughterhouse, with such precautions as are possible to prevent dissemination of the contagion. The animals should be slaughtered under the supervision of an inspector. The healthy carca.s.ses may be utilized for food, but the blood, entrails, and all diseased carca.s.ses should be heated to a temperature equal to that of boiling water or above, and then used for the manufacture of fertilizers.

The disinfection of premises should be thorough and should be carried out by a trained corps of men employed for the purpose. The floors of stables should be removed, the acc.u.mulations removed from beneath them, the contents of haylofts should be destroyed, and the woodwork and soil beneath the stables should be thoroughly drenched with a solution of bichlorid of mercury, 1 part to 2,000 of water. After the flooring is replaced the woodwork should be coated with limewash, containing one-fourth pound of chlorid of lime to the gallon of mixture.

Usually in these cases the owners are dependent upon their herd of cows for a living, and consequently it is difficult or impossible to hold the stables vacant for any considerable period. In a majority of instances cattle may be admitted at once to stables so disinfected, without the reappearance of the disease. Occasionally, however, it will reappear without apparent cause. For this reason the inspection and other measures must be maintained in the infected district for six months or a year after the last case of disease has been disposed of.

Many people have objected to the slaughter of diseased and exposed animals as an unscientific and expensive method of eradicating the disease. To these it may be answered that it is the only method which has ever proved successful, and that in the end it is much more economical than temporizing measures.

Inoculation has been adopted in many countries, and has undoubtedly lessened the death rate, but where this practice is allowed the disease is kept up and spreads. For this reason it should be prohibited wherever there is a possibility and disposition to eradicate the contagion.

RINDERPEST.

Rinderpest, also known as cattle plague, is an acute, infectious disease of cattle, in which the digestive organs are mainly involved. Though unknown in this country, the importance of having near at hand a few definite facts concerning this disease, should it ever reach our sh.o.r.es, will be at once appreciated. A knowledge of such facts may aid in an early recognition of the disease. It must not be forgotten, on the other hand, that a superficial knowledge of diseases, such as the layman may gain through reading, not infrequently leads to confounding comparatively harmless, noninfectious maladies with such as are truly dangerous (foot-and-mouth disease, rinderpest, etc), and causes temporary panics among stock owners.

According to some authorities, rinderpest has its home in the territory around the Black Sea and the Volga River in Russia; according to others, in Central Asia. Thence it has been conveyed at various times by cattle to nearly every country of Europe and Asia, where it has proved to be a veritable bovine scourge. It probably visited Europe as early as the beginning of the Christian era, and since then the migrations of the people from the Far East have from time to time introduced the disease. Especially during the eighteenth century it was more or less prevalent in Europe, owing to the frequent wars, during which herds of cattle were brought from eastern Europe and Asia to supply the demands of the armies. It prevailed in Europe during the Franco-Prussian War. At present it exists in eastern Europe and in portions of Asia and Africa.

The virus is conveyed from one country to another chiefly by means of infected cattle, although infected hides, wool, and feed may play an important part in its dissemination. The railroad facilities of the present, which furnish the means of such rapid communication, are particularly liable to aid in the spread of the disease.

In the past rinderpest has been supposed to be identical with various human diseases, among them smallpox and typhoid fever. These suppositions are unfounded, and the view of authorities to-day is that it is a disease of a peculiar kind, not identical with any other known infectious disease.

_The contagion of rinderpest._--The cause of rinderpest must be looked for among microorganisms--most likely bacteria. The investigations made thus far for this causal factor have been fruitless. However, certain recent experiments would indicate that the unseen microbe is of such dimensions that it is withheld by the dense bacterial filters, but pa.s.ses through the more porous ones. Formerly it was supposed by various authorities that rinderpest virus appeared spontaneously under the influence of deteriorated feed and long and exhausting drives; also during unusual meteorological conditions. This view, however, is no longer maintained. It is probable that in its home in Asia the disease is perpetuated by continual infection of fresh animals, and some authorities go even so far as to believe that the disease would be entirely stamped out, even in its native haunts, by a destruction of all sick and infected herds. However this may be, the success of such an undertaking would largely depend on the nature of the cause. If a strictly parasitic organism, like the contagion of pleuropneumonia, it might be completely extirpated in this way. If, however, the germs or bacteria may live and multiply outside of the bovine body, in the soil, water, or in some other animal, extirpation would be impossible.

The virus may be transmitted in a variety of ways, both direct and indirect, from sick to healthy animals. It is said to be present in the various excreta, such as the discharges from the nose, and the saliva, the urine, and the manure, of the diseased. For months it retains its vitality in a moist state outside the body, and the disease is reported to have developed after feeding hay a year after it had lain in an infected stable; hence manure and the fodder and bedding soiled with discharges may convey it. Persons may carry the virus on their shoes, clothing, or implements.

Even small animals, such as cats and rats, which frequent barns and stables, have been looked upon as carriers of the virus.

Cattle are very susceptible to the disease, and in its virulent type all those exposed are said to become infected. Buffaloes, sheep, and goats are likewise susceptible, but in a less degree.

It is also claimed that animals after having pa.s.sed through one attack successfully resist future attacks. Inoculation with virus is said to produce immunity, but in many cases the process of inoculation itself is followed by death.

_Symptoms._--The symptoms of rinderpest are not very characteristic, and hence the diagnosis of a suspected case in the beginning of an invasion is attended with difficulties. Certain appearances which are characteristic of one epizootic may be absent in another. Different observers are not quite agreed as to the most constant and important.

The period of incubation, i. e., the time between the exposure to infection and the earliest outward symptoms, varies from three to nine days. The first sign is a very high fever, which may reach 107 F. The heat of the skin varies in different parts of the body, and may be felt at the base of the ears and horns. Repeated chills are frequently observed. The pulse reaches 50 to 60 beats a minute, and in very severe attacks may rise to 90 or 100.

The animal manifests great debility. The head droops and rests on some object of support. One or both ears may droop. The coat is staring and the muzzle dry. The secretion of milk diminishes very rapidly. Within twelve to twenty hours the usual quant.i.ty may have become reduced one-half or two-thirds. The back is arched, and the four limbs are brought together under the body.

As the disease progresses, symptoms with reference to the digestive and respiratory organs become prominent. The mucous membrane of the mouth and the nose, as well as that of the r.e.c.t.u.m and v.a.g.i.n.a, becomes reddened, either in patches or diffusely, and a.s.sumes a scarlet hue. The discharges, at first firm, become softer, and soon diarrhea sets in. This is said to be one of the most constant symptoms. The r.e.c.t.u.m may become everted and paralyzed, and the bowels move spontaneously. The discharges become fetid, viscid, and streaked with blood. Coughing is a common symptom, and by some is considered characteristic. It is a.s.sociated with discharges from the nose and v.a.g.i.n.a and dribbling of saliva from the mouth. The eyes also are affected. There is an increased formation of a viscid secretion which flows down the face.

Another series of changes prominent in some epizootics and mild or absent in others are the ulcers, or so-called "erosions," in the mouth. These begin as red patches and streaks. The mucous membrane in such localities is converted into a grayish-white slough, which, when shed, leaves a small erosion, or ulcer. At the same time similar changes may go on in the skin of the thighs, the udder, or the s.c.r.o.t.u.m, or about the v.a.g.i.n.a, which lead to small sloughs.

In severe cases, which are the most common in the susceptible cattle of western Europe, death ensues four to seven days after the first appearance of the disease, and is preceded by great emaciation and debility, fetid, purulent discharges from the nose and mouth, and the relaxed r.e.c.t.u.m and v.a.g.i.n.a.

After death, if the animal is opened and the organs carefully examined, the chief changes are found in the digestive organs. The lining membrane of the mouth and pharynx is covered with mucus, is reddened in spots, and shows superficial, yellowish-gray, cheesy patches, which represent dead tissue, and when removed expose ulcerated depressions. The same reddening in spots and the yellowish-gray, cheesy deposits or patches are found in the fourth stomach, the small intestines, and more rarely in the cec.u.m, while the third stomach, or manyplies, is more or less impacted with dry, hard feed.

Similar changes may be found on the mucous membrane of the nasal cavity, larynx, trachea, the uterus, v.a.g.i.n.a, and r.e.c.t.u.m. The lungs may be injected, edematous, or pneumonic. The heart muscle is pale and flabby, and frequently hemorrhages are observed in its internal membrane. The liver may be pale or injected with blood, and at times shows hemorrhages beneath its capsule. The bile is thin and watery in consistence. The kidneys may be inflamed or contain small hemorrhages within their substance or under the capsule. The lymphatic glands may be swollen and injected or even hemorrhagic.

_Treatment._--On account of the danger of spreading the infection, neither medicinal treatment nor inoculation is permitted in European countries, with the exception of Russia, where the disease is more generally diffused.

The most effective method of exterminating rinderpest in those districts in which the disease is not indigenous has been found to be the slaughter of all affected and exposed animals. Where the disease is general, successful efforts adopted for its control have followed the immunization by inoculation of the exposed animals and a strict application of appropriate sanitary measures. This protective inoculation has been practiced with very gratifying results in Russia, South Africa, and in the Philippine Islands.

An active immunity is thus induced in susceptible animals which lasts until the danger from exposure to the disease is over. This immunity may be attained (1) by the inoculation of pure bile from an animal which recently died of rinderpest, (2) by the inoculation of glycerinated bile, followed by pure bile or virulent blood, or (3) by the simultaneous inoculation of strong standardized serum and virulent blood.

The latter method has been adopted by the United States Government in its endeavor to exterminate the disease in the Philippines, and to protect the cattle and carabaos against rinderpest after their importation into those islands. Owing to the existence of this and other infectious diseases in the Philippine Islands, an order has been issued by the Department of Agriculture prohibiting the landing of any live stock or animals of any kind from the Philippines at any of the ports of the United States or the dependencies thereof. This prohibition removes the greatest source of danger to which the United States is exposed as the result of its intercourse with the islands. The introduction of rinderpest from those countries from which we import animals is rendered extremely improbable, especially in live animals, owing to its short period of incubation and to the 90-day quarantine for cattle (counting from date of shipment) and 15-day (counting from date of landing) quarantine for sheep and other ruminants and swine which are at present enforced in the United States at all ports of entry.

FOOT-AND-MOUTH DISEASE.

[Pl. x.x.xIII.]

Foot-and-mouth disease, also known as aphthous fever, epizootic aphtha, and eczema contagiosa, is an acute, highly communicable disease chiefly confined to cloven-footed animals and characterized by an eruption of vesicles or blisters on the mucous membrane of the mouth and on the skin between the toes and above the hoofs. The vesicles rupture, forming erosions and ulcerations; there are also salivation, tenderness of the affected parts, loss of appet.i.te, lameness, emaciation, and diminution in the quant.i.ty of milk secreted.

The tremendous ravages of the disease are seen in the number and variety of the species attacked. While it may be regarded as essentially a disease of cattle, hogs would seem to be as easy a prey. Almost in the same grade of receptivity are sheep and goats. Next in order of susceptibility come the buffalo, American bison, camel, chamois, llama, giraffe, and antelope.

Horses, dogs, cats, and even poultry may occasionally become infected with the disease, the last three being particularly dangerous as carriers of the contagion. Man himself is not immune, and the frequency of his infection by coming in contact with diseased animals is established by numerous observations.

As with other communicable diseases, the source and origin of foot-and-mouth disease have given rise to much speculation. The disease had been known in Europe for centuries, but it was not until comparatively recent years that the erroneous conceptions of its spontaneous origin as a result of climatic and meteorological conditions, exhausting journeys, etc., were abandoned. It is now conceded that foot-and-mouth disease is propagated by a specific virus and that every outbreak starts from some preexisting outbreak.

So far investigators have been unable to identify or isolate the specific organism causing the disease, although numerous attempts have been made to cultivate and stain it by laboratory methods. Experiments have shown that the virus will pa.s.s through standard germ-proof filters, thus indicating its minute size and the reason it has not been detected by the staining methods. The contagion may be found in the serum of the vesicles on the mouth, feet, and udder; in the saliva, milk, and various secretions and excretions; also in the blood during the rise of temperature.

A wide distribution of the virus and a rapid infection of a herd is the result. Animals may be infected directly, as by licking, and in calves by sucking, or indirectly by such things as infected manure, hay, utensils, drinking troughs, railway cars, animal markets, barnyards, and pastures.

Human beings may carry the virus on their shoes and clothing and transmit it on their hands when milking, since the udder is occasionally the seat of the eruption. It may also be carried by dogs, cats, rats, chickens, pigeons, etc. Milk in a raw state may also transmit the disease to animals fed with it.

The observations made by some veterinarians would lead us to suppose that the virus is quite readily destroyed. It is claimed that stables thoroughly cleaned become safe after drying for a short time; hence, litter of all kinds, such as manure or soiled hay and straw, may remain infective for a longer time because they do not dry out. Other authorities maintain that the virus is quite tenacious and may live in stables even so long as a year. They also state that animals which have pa.s.sed through the disease may be a source of infection for several months after recovery.

Unlike most other infectious diseases, foot-and-mouth disease may repeatedly attack the same animals. The immunity conferred by an attack is of limited duration.

The period of incubation (that is, the time between the exposure of an animal to infection and the development of the disease) is variable, usually from three to six days. The disease may appear in 24 hours, or, in exceptional cases, not for 18 days or even longer.

_Losses._--The highly contagious character of foot-and-mouth disease and its rapid spread to practically all exposed susceptible animals lead to heavy losses. Since the mortality is comparatively low, ranging from only 3 per cent or less in mild forms to 30 or 40 per cent in malignant cases, the havoc caused by the pestilence is sometimes underestimated. But there are other sources of loss which are much more important than the actual mortality. The fever and the difficulty of eating cause a rapid and extreme loss in flesh and a lessening or cessation of the milk secretion. The udders often become inflamed and ruined by the formation of abscesses, and cows affected in this way are sometimes rendered permanently valueless for milk production. The inflammation of the feet may cause the horn to drop from the toes, producing great lameness and lasting injury. Abortion is frequent, and typical lesions have been observed in the newly born at birth. Altogether these losses may amount to 20 or 30 per cent of the value of the affected animals.

In addition there are indirect losses of a commercial nature. Dairy farmers are put out of business for a time. Necessary quarantine restrictions greatly interfere with the movement of live stock and such commodities as hay, straw, hides, and farm produce. The business of the stockyards and slaughtering centers is greatly interfered with. Sometimes it is necessary to close stockyards for disinfection. The whole business of marketing, transporting, feeding, and slaughtering is interrupted and deranged. Losses of this character may reach enormous proportions.