Chapter XXVII: Part 27

These wounds of domestic animals are fortunately of rare occurrence; however, when they do occur, if at all extensive, they prove to be quite troublesome and in many cases are fatal. According to the severity of the burn we distinguish three degrees: First degree, where there is a simple reddening of the skin; second degree, where there is a formation of vesicles, or blisters; third degree, where there is a complete destruction of vitality of the tissues, such as would occur in charring from direct contact with flames or from escaping steam. Besides the burns caused by flames and steam, there are other causative agents, such as chemicals (caustic alkalis and acids), lightning stroke, and occasionally the broken trolley wires of electric railways. When a large surface of the skin is burned or scalded, the animal (if it does not die at once from shock) will soon show signs of fever--shivering, coldness of the extremities, weakness, restlessness, quick and feeble pulse, and labored breathing. No matter which agent is a factor in the production of burns, the lesions are practically of the same nature. The extent and site of the burn should lead one in the determination and course of treatment. Burns of the shoulder and those about the region of the elbow or other parts where there is much movement of the tissues are grave, and, if at all extensive, treatment should not be attempted, but the immediate destruction of the animal is advised. A burn of the third degree, where there is a destruction of the vitality of large areas of tissue, even on parts not subject to much motion, is extremely tedious to treat; in fact, it is questionable whether the treatment and keep of the animal will ever be compensated for, even though recovery does take place; this, in any event, will require at least six or eight weeks. Burns caused by lightning stroke and trolley wires are liable to occur in irregular lines, and, unless death occurs at once, they generally are not serious.

_Treatment._--Treatment should be prompt and effective. If the burns are extensive, the constitutional symptoms should be combated with whisky and milk and eggs, or ammonia carbonate, strychnin, caffein, or other stimulant to prevent shock. In the local treatment, to alleviate the pain, the application of cold water in some form and the hypodermic injection of morphine are to be recommended. In burns of the first degree, where there is only a superficial inflammation, lead carbonate (white lead) ointment is very good. Carron oil (limewater and linseed oil, equal parts) is a standard remedy, but a modification of it known as Stahl's liniment is perhaps better. This is composed of linseed oil and limewater each 200 parts, bicarbonate of soda 100 parts, and thymol 1 part. The scorched surface should be covered with this liniment and then with a layer of borated gauze or absorbent cotton, to protect from the air. The application should be frequently renewed. Carbolated vaseline may be used in place of the above. In case the burn is more extensive, the following solution may be used: Picric acid 2 parts, alcohol 40 parts, water 400 parts. The lesion should be thoroughly cleansed with this solution used on absorbent cotton. The vesicles, if any appear, should be opened with a clean needle, allowing the skin to remain. Strips of gauze or absorbent cotton saturated with the solution should now be applied and renewed only occasionally. In burns of the second and third degrees more satisfactory results may be obtained with nonpoisonous, dry dressing powder, such as is used in ordinary open wounds, as tannic acid 8 parts and iodoform 1 part, or a salve made of this powder and a sufficient quantity of vaseline. When sloughing of the tissues takes place the wounds should be cleansed with a warm 3 per cent solution of carbolic acid, all loose fragments of tissue removed, and either a dry, antiseptic dressing powder or carbolated vaseline ointment applied to exclude the air. Granulation tissue (proud flesh) should be controlled by the application of silver nitrate in the form of a caustic pencil.

Burns due to mineral acids may be first treated by flushing the parts with a copious quantity of cold water or by the application of whiting or chalk. Either use a large quantity of water at the start or use the chalk first, then wash with water. If the irritant has been a caustic alkali, such as potash, lye, ammonia, or soda, then vinegar should be the first application. Stahl's liniment is probably the best general application for all burns for the first week; then this should be followed by the ordinary antiseptic wound dressings.

GANGRENE.

Gangrene, or mortification, denotes the death of the affected part, and is mostly found attacking soft tissue near the surface of the body. Gangrenous areas may occur as a result of shutting off their blood supply. Constitutional diseases, such as ergotism, anthrax, and septicemia, predispose to gangrene. As external causes we have acids and alkalies, freezing and burning, contusions and continuous pressure that interrupt the circulation. There are two forms of gangrene--dry and moist. Dry gangrene is most often seen in horses from continuous lying down (decubitus) or from uneven pressure of some portion of the harness.

_Symptoms._--There is a lack of sensation due to the death of nerves. In dry gangrene the skin is leathery and harsh, while in moist gangrene the tissues are soft, wrinkled, and friable; the hair is disturbed, and the skin is usually moist and soapy and sometimes covered with blebs. The tissue surrounding the moist gangrenous patch is usually inflamed, swollen, and hot, but this is less noticeable in the case of dry gangrene. Moist gangrene often spreads and involves deeper tissue, sheaths of tendons and joints producing septic synovitis or septic arthritis leading to pyemia and death. Dry gangrene is seldom dangerous, but the rapidity of its spread will indicate its virulence.

_Treatment._--The preventive treatment consists in avoiding all the influences that tend to disturb the nutrition of the tissues, such as excessive cold or heat or continuous pressure. Gangrene following decubitus may be prevented by using soft bedding and frequently turning the animal from one side to the other. In dry gangrene moist heat in the form of poultices or anointing the tissue with oils and fats will be found beneficial in hastening the dead tissue to slough off. When the outer skin begins to suppurate, it should be removed with a pair of pincers, and the patch treated as an open wound. In moist gangrene the tissue should be thoroughly disinfected with a 3 per cent solution of compound cresol, or particularly an alcoholic tincture of camphor. Continuous irritation with antiseptic fluids prevents the accumulation and absorption of poisonous liquids. Incisions into the dead tissue may be made, and when sloughing commences the tissue should be removed with forceps and the resulting wound treated as in dry gangrene.

ULCERATION.

An ulcer is a circumscribed area of necrosis occurring on the skin or mucous membrane and covered with granulation tissue. It is a process of destruction, and when this process is going on faster than regeneration can take place, we have a gnawing, or eating, ulcer. When such an ulcer increases rapidly in size it is termed a phagedenic ulcer. A fungoid ulcer is one in which the bottom of the ulcer projects beyond the edge of the skin. These ulcers secrete milky or bloody-white liquid called ichor. When the ulcer is of an ashen or leaden color, with the bottom and sides formed of dense, hard connective tissue, which gives but little discharge and is not sensitive, it is termed callous, torpid, or indolent ulcer.

_Causes._--As in the case of gangrene, disturbances of circulation are among the most frequent causes. A wound to a tissue with slight recuperative power may be followed by ulceration, as in tumors. Certain germs may produce ulcers, as the glanders bacilli, which cause the ulcerations on the nasal septum in glanders.

_Treatment._--This consists in removing the exciting cause at once. The secretions of the ulcer should be washed off with antiseptic solutions and the formation of granulation tissues stimulated by antiseptic salves, such as carbolated vaseline, lead ointment, or by dressings of camphor. Air should be kept from the ulcer by occlusive dressings. Where the ulcers are inflamed, warm lead water or lead water and laudanum will be found efficacious. Callous ulcers are best removed by a curette, knife, or hot iron and then treated like a common wound. Mechanical irritation should be avoided.

ABSCESSES.

These consist of accumulations of pus within circumscribed walls, at different parts of the body, and may be classed as acute and cold or chronic abscesses.

When an abscess occurs about a hair follicle it is called a boil or furuncle; when several hair follicles are involved, resulting in the formation of more than one exit for the inflammatory products, it is called a carbuncle.

ACUTE ABSCESSES.

Acute abscesses follow as the result of local inflammation in glands, muscular tissue, or even bones. They are very common in the two former. The abscesses most commonly met with in the horse (and the ones which will be here described) are those of the salivary glands, occurring during the existence of "strangles," or "colt distemper." The glands behind or under the jaw are seen to increase slowly in size, becoming firm, hard, hot, and painful. At first the swelling is uniformly hard and resisting over its entire surface, but in a little while becomes soft (fluctuating) at some portion, mostly in the center. From this time on the abscess is said to be "pointing," or "coming to a head," which is shown by a small elevated or projecting prominence, which at first is dry, but soon becomes moist with transuded serum. The hairs over this part loosen and fall off, and in a short time the abscess opens, the contents escape, and the cavity gradually fills up--heals by granulations.

Abscesses in muscular tissue are usually the result of bruises or injuries. In all cases in which abscesses are forming we should hurry the ripening process by frequent hot fomentations and poultices. When they are very tardy in their development a blister over their surface is advisable. It is a common rule with surgeons to open an abscess as soon as pus can be plainly felt, but this practice can scarcely be recommended indiscriminately to owners of stock, since this little operation frequently requires an exact knowledge of anatomy. It will usually be found the better plan to encourage the full ripening of an abscess and allow it to open of itself. This is imperative if the abscess is in the region of joints, etc. When open, we must not squeeze the walls of the abscess to any extent. They may be very gently pressed with the fingers at first to remove the clots--inspissated pus--but after this the orifice is simply to be kept open by the introduction of a clean probe, should it be disposed to heal too soon. If the opening is at too high a level another should be made into the lowest portion of the abscess so as to permit the most complete drainage. Hot fomentations or poultices are sometimes required for a day or two after an abscess has opened, and are particularly indicated when the base of the abscess is hard and indurated.

The cavity should be thoroughly washed with stimulating antiseptic solutions, such as 3 per cent solution of carbolic acid, 3 per cent solution of compound cresol, 1 to 1,000 bichlorid of mercury, or 1 per cent permanganate of potash solution. If the abscesses are foul and bad smelling, their cavities should first be syringed with 1 part of hydrogen peroxid to 2 parts of water and then followed by the injection of any of the above-mentioned antiseptics.

COLD ABSCESSES.

Cold abscess is the term applied to those large, indolent swellings that are the result of a low or chronic form of inflammation, in the center of which there is a small collection of pus. They are often seen near the point of the shoulder, forming the so-called breast boil. The swelling is diffuse and of enormous extent, but slightly hotter than surrounding parts, and not very painful upon pressure. A pronounced stiffness, rather than pain, is evinced upon moving the animal. Such abscesses have the appearance of a hard tumor, surrounded by a softer edematous swelling, involving the tissues to the extent of a foot or more in all directions from the tumor. This diffused swelling gradually subsides and leaves the large, hardened mass somewhat well defined. One of the characteristics of cold abscesses is their tendency to remain in the same condition for a great length of time. There is neither heat nor soreness; no increase nor lessening in the size of the tumor; it remains in statu quo. If, however, the animal should be put to work for a short time the irritation of the collar causes the surrounding tissues to assume again an edematous condition, which after a few days' rest disappears, leaving the tumor as before or but slightly larger. Upon careful manipulation we may discover what appears to be a fluid deep seated in the center of the mass. The quantity of matter so contained is very small--often not more than a tablespoonful--and for this reason it can not, in all cases, be detected.

Cold abscesses are mostly, if not always, caused by the long-continued irritation of a loose and badly fitting collar. There is a slow inflammatory action going on, which results in the formation of a small quantity of matter inclosed in very thick and but partially organized walls that are not so well defined as is the circumference of fibrous tumors, which they most resemble.

_Treatment._--The means recommended to bring the acute abscess "to a head" are but rarely effectual with this variety; or, if successful, too much time has been occupied in the cure. We must look for other and more rapid methods of treatment. These consist, first of all, in carefully exploring the tumor for the presence of pus. The incisions must be made over the softest part and carried deep into the tumor--to its very bottom, if necessary--and the matter allowed to escape. After this, and whether we have found matter or not, we must induce an active inflammation of the tumor, in order to promote solution of the thick walls of the abscess. This may be done by inserting well into the incision a piece of oakum or cotton saturated with turpentine, carbolic acid, tincture of iodin, etc., or we may pack the incision with powdered sulphate of zinc and keep the orifice plugged for 24 hours. These agents set up a destructive inflammation of the walls. Suppuration follows, and this should now be encouraged by hot fomentations and poultices. The orifice must be kept open, and should it be disposed to heal we must again introduce some of the agents above described. A favored treatment with many, and it is probably the best, is to plunge a red-hot iron to the bottom of the incision and thoroughly sear all parts of the walls of the abscess. This is to be repeated after the first slough has taken place if the walls remain thickened and indurated.

It is useless to waste time with fomentations, poultices, or blisters in the treatment of cold abscesses, since though apparently removed by such methods, they almost invariably return when the horse is put to work. Extirpation by the knife is not practicable, as the walls of the tumor are not sufficiently defined. If treated as above directed, and properly fitted with a good collar after healing, there will not remain any track or trace of the large, unsightly mass.

FISTULAS.

_Definition._--The word fistula is applied to any ulcerous lesion upon the external surface of the body which is connected by ducts, or passages, with some internal cavity. Because of this particular formation the term fistulous tract is often used synonymously with the word fistula. Fistulas may exist in any part of the body, but the name has come to be commonly accepted as applicable only to such lesions when found upon the withers. Poll evil is a fistula upon the poll, and in no sense differs from fistulous withers except in location. The description of fistula will apply, then, in the main, to poll evil equally well. Quittor presents the characteristic tubular passages of a fistula and may, therefore, be considered and treated as fistula of the foot. Fistulous passages may also be developed upon the sides of the face, through which saliva is discharged instead of flowing into the mouth, and are called salivary fistulas. A dental fistula may arise from the necrosis of the root of a tooth. Again, a fistula is sometimes noted at the umbilicus associated with hernia, and recto-vaginal fistulas have been developed in mares, following difficult parturition. Fistulas may arise from wounds of glandular organs or their ducts, and thus we have the so-called mammary or lacrimal fistulas.

Fistulous tracts are lined with a false, or adventitious, membrane and show no disposition to heal. They constantly afford means of exit to the pus or ichorous material discharged by the unhealthy parts below. They are particularly liable to develop at the withers or poll because of the exposed positions which these parts occupy, and, having once become located there, they usually assert a tendency to further extension, because the vertical and laminated formation of the muscles and tendons of these parts allows the forces of gravitation to assist the pus in gaining the deeper-lying structures and also favors its retention among them.

_Causes._--Fistulas follow as a result of abscesses, bruises, wounds, or long-continued irritation by the harness. Among the more common causes of fistula of the poll (poll evil) are chafing by the halter or heavy bridle; blows from the butt end of the whip; the horse striking his head against the hayrack, beams of the ceiling, low doors, etc. Fistulous withers are seen mostly in those horses that have thick necks as well as those that are very high in the withers; or, among saddle horses, those that are very low in the withers, the saddle here riding forward and bruising the parts. In either of these locations ulcers of the skin, or simple abscesses, if not properly and punctually treated, may become fistulas. They are often caused by bad-fitting collars or saddles, by direct injuries from blows, and from the horse rolling upon rough or sharp stones. The pus burrows and finds lodgment deep down between the muscles, and escapes only when the sinus becomes surcharged or when, during motion of the parts, the matter is forced to the surface.

_Symptoms._--These, of course, will vary according to the progress made by the fistula. Following an injury we may often notice soreness or stiffness of the front legs, and upon careful examination of the withers we see small tortuous lines running from the point of irritation downward and backward over the region of the shoulder. These are superficial lymphatics, and are swollen and painful to the touch. In a day or two a swelling is noticed on one or both sides of the dorsal vertebrae, which is hot, painful, and rapidly enlarging. The stiffness of the limbs may disappear at this time, and the heat and soreness of the parts may become less noticeable, but the swelling remains and continues to enlarge.

A fistulous ulcer of the poll may be first indicated by the opposition which the animal offers to the application of stable brush or bridle. At this time the parts are so sore and sensitive that there is some danger that unless handled with the greatest care the patient will acquire disagreeable stable habits. The disease in its early stages may be recognized as a soft, fluctuating tumor surrounded by inflammatory swelling, with the presence of enlarged lymphatic vessels and stiffness of the neck. Later the inflammation of the surrounding tissues may disappear, leaving a prominent tumor. The swelling, whether situated upon the head or the withers, may open and form a running ulcer, or its contents may dry up and leave a tumor which gradually develops the common characteristics of a fibrous tumor. When the enlargement has opened we should carefully examine its cavity, as upon its condition will wholly depend our treatment.

_Treatment._--In the earliest stage, when there is soreness, enlarged lymphatics, but no well-marked swelling, the trouble may frequently be aborted. To do this requires both general and local treatment. A physic should be given, and the horse receive 1 ounce of powdered saltpeter three times a day in his water or feed. If the fever runs high, 20-drop doses of tincture of aconite root every two hours may be administered. The local application of cold water to the inflamed spot for an hour at a time three or four times a day has often proved very beneficial, and has afforded great relief.

Cooling lotions, muriate of ammonia, or saltpeter and water; sedative washes, such as tincture of opium and aconite, chloroform liniment, or camphorated oil, are also to be frequently applied. Should this treatment fail to check the progress of the trouble, the formation of pus should be hastened as rapidly as possible. Hot fomentations and poultices are to be constantly used, and as soon as the presence of pus can be detected, the abscess wall is to be opened at its lowest point. In this procedure lies our hope of a speedy cure. As with any simple abscess, if drainage can be so provided that the pus will run off as fast as formed without remaining within the interstices of the tissues, the healing will be rapid and satisfactory.

Attention is again called to the directions given above as to the necessity of probing the cavity when opened. If upon a careful examination with the probe we find that there are no pockets, no sinuses, but a simple, regular abscess wall, the indication for treatment is to make an opening from below so that all the matter must escape. Rarely is anything more needed than to keep the orifice open and to bathe or inject the parts with some simple antiseptic wash that is not irritant or caustic. A low opening and cleanliness constitute the essential and rational treatment.

If the abscess has already opened, giving vent to a quantity of purulent matter, and the pipes and tubes leading from the opening are found to be extensive and surrounded with thick fungoid membranes, there is considerable danger that the internal ligaments or even some of the bones have become affected, in which case the condition has assumed a serious aspect. Or, on the other hand, if the abscess has existed for some time without a rupture, its contents will frequently be found to consist of dried purulent matter, firm and dense, and the walls surrounding the mass will be found greatly thickened. In such a case we must generally have recourse to the application of caustics which will cause a sloughing of all of the unhealthy tissue, and will also stimulate a rapid increase of healthy organized material to replace that destroyed in the course of the development and treatment of the disease. Threads or cords soaked in gum-arabic solution and rolled in powdered corrosive sublimate may be introduced into the canal and allowed to remain. The skin on all parts of the shoulder and leg beneath the fistula should be carefully greased with lard or oil, as this will prevent the discharge that comes from the opening after the caustic is introduced from irritating or blistering the skin over which it flows. In obstinate cases a piece of caustic potash (fused) 1 to 2 inches in length may be introduced into the opening and should be covered with oakum or cotton. The horse should then be secured so that he can not reach the part with his teeth. After the caustic plug has been in place for 24 hours, it may be removed and hot fomentations applied. As soon as the discharge has become again established the abscess should be opened from its lowest extremity, and the passage thus formed may be kept open by the introduction of a seton. If the pipes become established in the deep tissues beneath the shoulder blade or among the spines of the vertebral column, it will often be found impossible to provide proper drainage for the abscess from below, and treatment must consist of caustic solutions carefully injected into all parts of the suppurating sinuses. A very effective remedy for this purpose consists of 1 ounce of chlorid of zinc in half a pint of water, injected three times during a week, after which a weak solution of the same may be occasionally injected. Injections of Villate's solution or alcoholic solution of corrosive sublimate, strong carbolic acid, or possibly oil of turpentine will also prove beneficial. Pressure should be applied from below, and endeavors made to heal the various pipes from the bottom.

Should the swelling become general, without forming a well-defined tumor, the placing of 20 to 30 grains of arsenious acid, wrapped in a single layer of tissue paper, in a shallow incision beneath the skin, will often produce a sloughing of the affected parts in a week or 10 days, after which the formation of healthy tissue follows. The surrounding parts of the skin should be protected from any damage from escaping caustics by the application of lard or oil, as previously suggested.

Although the successful treatment of fistulas requires time and patience, the majority of cases are curable. The sinuses must be opened at their lowest extremity and kept open. Caustic applications must be thoroughly used once or twice, after which mild astringent antiseptic washes should be persistently used until a cure is reached.

It sometimes happens that the erosions have burrowed so deeply or in such a direction that the opening of a drainage passage becomes impracticable. In other cases the bones may be attacked in some inaccessible location, or the joints may be affected, and in these cases it is often best to destroy the horse at once.

The reappearance of the fistula after it has apparently healed is not uncommon. The secondary attack in these cases is seldom serious. The lesion should be carefully cleaned and afterwards injected with a solution of zinc sulphate, 20 grains to the ounce of water, every second or third day until a cure is effected.

In fistula of the foot we see the same tendency toward the burrowing of pus downward to lower structures, or in some cases upward toward the coronet. Prior to the development of a quittor there is always swelling at the coronet, accompanied with heat and pain. Every effort should now be made to prevent the formation of an abscess at the point of injury. Wounds caused by nails, gravel, or any other foreign body which may have lodged in the sole of the foot should be opened at once from below, so as to allow free exit to all purulent discharges. Should the injury have occurred directly to the coronet the application of cold fomentations may prove efficient in preventing the formation of an abscess.

When a quittor becomes fully established it should be treated precisely as a fistula situated in any other part of the body; that is, the sinuses should all be opened from their lowest extremities, so as to afford constant drainage. All fragments of diseased tissue should be trimmed away, antiseptic solutions injected, and, after covering the wound with a pad of oakum saturated with some good antiseptic wash, the whole foot may be carefully covered with clean bandages, which will afford valuable assistance to the healing process by excluding all dirt from the affected part.

Another form of treatment for this class of infections consists in the use of bacterial vaccines. Such treatment appears to be well adapted for the purpose, and according to current veterinary literature has met with success. These vaccines are composed of several strains of the organisms usually found in these pustular infections of the horse. Two kinds of vaccines are used: First, autogenic vaccines, which consist of heated (killed) cultures of the organism or organisms which are causing the trouble and which have been isolated from the lesions; second, stock vaccines, consisting of dead organisms of certain species generally found in these lesions and which are used in diseased conditions caused by one or the other of these germs. The vaccine is administered subcutaneously by means of a syringe, but the quantity of the vaccine to be injected and the number of doses to be used should be left to the judgment of a competent veterinarian.

INFECTIOUS DISEASES.

By RUSH SHIPPEN HUIDEKOPER, M. D., Vet.

[Revised by A. Eichhorn, D. V. S.]

GENERAL DISCUSSION.

An infectious disease may be defined as any malady caused by the introduction into the body of minute organisms of the vegetable or animal kingdom which have the power to multiply indefinitely and set free certain peculiar poisons which are chiefly responsible for morbid changes. Nearly all diseases of animals for which a definite cause may be attributed are caused by bacteria; such are tuberculosis, anthrax, blackleg, lockjaw, and others. There are some diseases, as, for instance, Texas fever and rabies, which are caused by a minute animal parasite known as protozoa, while others again, like lumpy jaw and aspergillosis, are caused by fungi. Besides there are infectious diseases in which the causative agents have never been successfully isolated, as they are so small that they can not be detected by the aid of the most powerful microscope, and accordingly they are termed as ultravisible viruses. Hog cholera, foot-and-mouth disease, smallpox, and others belong to this group.

Bacteria may be defined as very minute unicellular organisms of plantlike character. They multiply either by simple division or by spore formation, the latter usually taking place when the conditions pertaining to the growth of the bacteria become unfavorable. The spores are much more resistant to destruction than the bacteria which produce them.

Another group of parasites producing disease is known as protozoa. These are more complex than bacteria, and their artificial cultivation is also much more difficult than is the case with the bacterial parasites. Of the representatives of this group, causing disease in animals, are the trypanosomes, which are the causative factors of dourine and surra, and the piroplasma, which induce Texas fever in cattle and malaria or biliary fever of horses. There are also disease-producing fungi which are responsible for certain affections in horses; among these the most important are mycotic lymphangitis, or sporotrichosis, and streptotrichosis.

The introduction of the infection may take place in various ways. The most frequent method is by ingestion. Further, the entrance of the germs may occur by inhalation, skin abrasions, wounds of any kind, through the genital organs, and at times also through the milk ducts of the teats. As a general rule infectious diseases have a period of incubation which comprises the time elapsing between the exposure to the infection and the actual appearance of the disease. This period varies in the different diseases.

The treatment of infectious diseases is, as a rule, unsatisfactory. When the symptoms have once appeared a disease is liable to run its course in spite of treatment, and if it is one from which animals usually recover, all that can be done is to put them into the most favorable surroundings. Many infectious diseases lead sooner or later to death; treatment is useless so far as the sick animals are concerned, and it may be worse than useless for those not yet affected. All animals suffering with infectious diseases are more or less directly a menace to all others. They represent for the time being manufactories of disease germs, and they are giving them off more or less abundantly during the period of disease. They may infect others directly or they may scatter the virus about and the surroundings may become the future source of infection.

Therefore, in the control of infectious diseases prevention is the most important procedure. The isolation or segregation of healthy animals from infected ones should be primarily considered, and if at any time an animal manifests the symptoms of an infectious disease it is essential to protect the others from such a source of danger. In some of the infectious diseases it may become advisable to kill the infected animals in order to avoid the spread of the disease. This is especially important in diseases which are slow in their course, such as tuberculosis. At times when diseases appear in a country where they have not been prevalent it becomes advisable and necessary to protect the healthy herds by the slaughter of all the infected animals. Pursuance of this policy has resulted in control of the foot-and-mouth disease, and has proved to be a very satisfactory method of eradication.

DISINFECTION.

Disinfection is a very important phase in the control of infectious disease. This consists in the use of certain substances which possess the power to destroy bacteria or their spores, or both. The cheapest and most available for animal diseases are ordinary freshly slaked lime, or unslaked lime in powder form, chlorid of lime, crude carbolic acid, corrosive sublimate, formalin, formaldehyde, gas, cresol, etc.

In the disinfection of stables and premises it is essential to execute the work in a most thorough manner. This may be satisfactorily accomplished by carrying out the following directions:

1. Sweep ceilings, side walls, stall partitions, floors, and other surfaces until free from cobwebs and dust.

2. Scrape away all accumulation of filth, and if woodwork has become decayed, porous, or absorbent, it should be removed, burned, and replaced with new material.

3. If floor is of earth, remove 4 inches from the surface, and in places stained with urine a sufficient depth should be replaced to expose fresh earth. All earth removed should be replaced with earth from an uncontaminated source; it would be better still to lay a new floor of concrete, which is very durable and easily cleaned.

4. All refuse and material from stable and barnyard should be removed to a place not accessible to cattle or hogs. The manure should be spread on fields and turned under, while the wood should be burned.

5. The entire interior of the stable, especially the feeding troughs and drains, should be saturated with a disinfectant, as liquor cresolis compositus (U. S. P.), or carbolic acid, 6 ounces to every gallon of water, to which 4 ounces of chlorid of lime should be added. The best method of applying the disinfectant and the lime wash is by means of a strong spray pump, such as those used by orchardists. This method is efficient in disinfection against most of the contagious and infectious diseases of animals, and should be applied immediately following any outbreak, and, as a matter of precaution, it may be used once or twice yearly.

6. It is important that arrangements be made to admit a plentiful supply of sunlight and fresh air by providing an ample number of windows, thereby eliminating dampness, bad odor, and other insanitary conditions. Good drainage is also very necessary.

If the use of liquor cresolis compositus, carbolic acid, or other coal-tar products is inadmissible because of the readiness with which their odor is imparted to milk and other dairy products, bichlorid of mercury may be used in proportion of 1 to 800, or 1 pound of bichlorid to 100 gallons of water. All portions of the stable soiled with manure, however, should first be thoroughly scraped and cleaned, as the albumin contained in manure would otherwise greatly diminish the disinfecting power of the bichlorid. Disinfection with this material should be supervised by a veterinarian or other person trained in the handling of poisonous drugs and chemicals, as the bichlorid is a powerful, corrosive poison. The mangers and the feed boxes, after drying, following spraying with this material, should be washed out with hot water, as cattle are especially susceptible to mercurial poisoning. The bichlorid solution should be applied by means of a spray pump, as recommended for the liquor cresolis compositus.

VACCINATION.

In recent years vaccination for the prevention of certain infectious diseases has been successfully developed, and without a doubt the future has a great deal in store for this phase of prevention. At the present time vaccination has been found effective against blackleg, hog cholera, anthrax, lockjaw, strangles, rabies, hemorrhagic septicemia, white scours, etc. It is always essential, of course, that the products used for the vaccination be pure and potent; also they should be employed only with the advice of competent authorities and with proper care. The biological products prepared for the cure and prevention of infections are prepared by manufacturers who, in order to conduct an interstate business, are required to obtain a license from the United States Department of Agriculture for the manufacture of such preparations.

Since July 1, 1913, the Department of Agriculture, by an act of Congress of March 4, 1913, has had control of the manufacture of biological products for the treatment of domestic animals. The numerous complaints which were received from time to time relative to the impotency of some of the preparations, and also the fact that in some instances the use of the products were directly responsible in causing outbreaks of disease, made the necessity for such control obvious. This supervision is no doubt of far-reaching importance, as it assures the users that the preparations are reliable.

INFLUENZA.

_Synonyms._--Pinkeye, typhoid fever, epizooty, epihippic fever,
hepatic fever, bilious fever, etc.; flevre typhoide, grippe
(French); Pferdestaupe (German); gastro-enteritis of Vatel and
d'Arboval; febris erysipelatodes, Zundel; typhus of Delafond.

_Definition._--The term influenza is applied to a febrile, contagious, infectious disease of horses, which is characterized by a blood infection, with inflammation of the mucous membranes, which frequently involves the lungs. Inflammatory complications also occur in the form of swellings of the subcutis, tendons, and tendinous sheaths and laminae of the feet. The causative agent has not been satisfactorily established. One attack usually protects the animal from future ones of the same disease, but not always. An apparently complete recovery is sometimes followed by serious sequelae of the nervous and blood-vessel systems. Under certain conditions of the atmosphere or from unknown causes, the disease is very liable to assume an epizootic form, with tendency to complications of especial organs, as, at one period, the lungs, at another the intestines, etc.

The first description of influenza is given by Laurentius Rusius in 1301, when it spread over a considerable portion of Italy, causing great loss among the war horses of Rome and the surrounding district. Later, in 1648, an epizootic of this disease visited Germany and spread to other parts of Europe. In 1711, under the name of "epidemica equorum," it followed the tracks of the great armies all over Europe, causing immense losses among the horses, while rinderpest was scourging the cattle of the same regions. The two diseases were confounded with each other, and were, by the scientists of the day, supposed to be allied to the typhus, which was a plague to the human race at the same time. We find the first advent of this disease to the British Islands in an epizootic among the horses of London and the southern counties of England in 1732, which is described by Gibson. In 1758 Robert Whytt recounts the devastation of the horses of the north of Scotland from the same trouble. Throughout the eighteenth century a number of epizootics occurred in Hanover and other portions of Germany and in France, which were renewed early in the present century, with complications of the intestinal tract, which obtained for it its name of gastro-enteritis. In 1766 it first attacked the horses in North America, but is not described as again occurring in a severe form until 1870-1872, when it spread over the entire country, from Canada south to Ohio, and then eastward to the Atlantic and westward to California. It is now a permanent disease in our large cities, selecting for the continuance of its virulence young or especially susceptible horses which pass through the large and ill-ventilated and uncleaned stables of dealers, and assumes from time to time an enzootic form, when from some reason its virulence increases. It assumes this form also when, from reasons of rural economy and commerce, large numbers of young and more susceptible animals are exposed to its contagion.

_Etiology._--The experiments of Dieckerhoff many years ago proved that the disease may be transmitted to healthy animals by intravenous injection of warm blood from affected horses.

Further investigations revealed the fact that blood from affected horses, even when passed through porcelain filters, may transmit the disease, thereby proving that the causative agent belongs to the so-called filterable viruses. This has been further substantiated by Gaffky, who showed in his recent experiments that the disease may be transmitted with defibrinated as well as with filtered blood, in which cases the typical form of influenza developed in inoculated animals in from five to six days. These findings were also substantiated by Basset. Further observations have also proved that apparently recovered animals may harbor the infection for a long time and still be capable of transmitting the disease. Such virus carriers are no doubt responsible for numerous outbreaks of this disease when, in a locality free from the disease, it certainly appears after the introduction of an apparently healthy animal.

As one attack is usually self-protective, numbers of old horses, having had an earlier attack, are not capable of contracting it again; but, aside from this, young horses, especially those about four or five years of age, are much more predisposed to be attacked, while the older ones, even if they have not had the disease, are less liable to it. Again, the former age is that in which the horse is brought from the farm, where it has been free from the risk of exposure, and is sold to pass through the stables of the country taverns, the dirty, infected railway cars, and the foul stockyards and damp stables of dealers in our large cities. Overfed, fat, young horses which have just come through the sales stables are much more susceptible to contagion than the same horses are after a few months of steady work.

Pilger, in 1805, was the first to recognize infection as the direct cause of the disease. Roll and others studied the contagiousness of influenza, and, finding it so much more virulent and permanent in old stables than elsewhere, classed it as a "stall miasm." The contagion will remain in the straw bedding and droppings of the animal and in the feed in an infected stable for a considerable time and if these are removed to other localities it may be carried in them. It may be carried in the clothing of those who have been in attendance on horses suffering from the disease. The drinking water in troughs and even running water may hold the virus and be a means of its communication to other animals, even at a distance.

The studies of Dieckerhoff, in 1881, in regard to the contagion of influenza were especially interesting. He found that during a local enzootic, produced by the introduction of infected horses into an extensive stable otherwise perfectly healthy, the infection took place in what at first seemed to be a most irregular manner, but which was shown later to be dependent on the ventilation and currents of air through the various buildings. His experiments showed that the virus of influenza is excessively diffusible, and that it will spread rapidly to the roof of a building and pass by the apertures of ventilation to others in the neighborhood. The writer has seen cases that have appeared to spread through a brick wall and attack animals on the opposite side before others even in the same stable were affected. Brick walls, old woodwork, and the dirt which is too frequently left about the feed boxes of a horse stall will hold the contagion for several days, if not weeks, and communicate it to susceptible animals when placed in the same locality. On two successive mornings a 4-year-old colt belonging to the writer stood for about 10 minutes at the open door, fully 40 feet from the stalls, of a stable in which two cases of influenza had broken out the day before: in six days the colt developed the disease. On the morning when the trouble in the colt was recognized it stood in an infirmary with a dozen horses that were being treated for various diseases, but was immediately isolated; within one week two-thirds of the other horses had contracted the disease.

_Symptoms._--After the exposure of a susceptible horse to infection a period of incubation of from four to seven days elapses, during which the animal seems in perfect health, before any symptom is visible. When the symptoms of influenza develop they may be intense, or so moderate as to occasion but little alarm, but the latter condition frequently exposes the animal to use and to the danger of the exciting causes of complications which would not have happened had it been left quietly in its stall in place of being worked or driven out to show to prospective purchasers. The disease may run a simple course as a specific fever, with alterations only of the blood, or at any period it may become complicated by local inflammatory troubles, the gravity of which is augmented by developing in an animal with an impoverished blood, an already irritated, rapid circulation, and defective nutritive and reparative functions.

The first symptoms are those of a rapidly developing fever, which becomes intense within a very short period. The animal becomes dejected and inattentive to surrounding objects; stands with its head down, and not back on the halter as in serious lung diseases. In the flanks, the muscles of the croup and of the shoulders, or of the entire body it has chills lasting from 15 to 30 minutes, and frequently a grinding of the teeth which warns one that a severe attack may be expected. The hairs become dry and rough and stand on end. The body temperature increases to 104 deg., 104.5 deg., and 105 deg. F., or even in severe cases to 107 deg. F., within the first twelve or eighteen hours. The horse becomes stupid, stands immobile with its head hanging, the ears listless, and it pays but little attention to the surrounding attendants or the crack of a whip. The stupor becomes rapidly more marked, the eyes become puffy and swollen with excessive lacrimation, so that the tears run from the internal canthus of the eye over the cheeks and may blister the skin in their course. The respiration becomes accelerated to 25 or 30 in a minute, and the pulse is quickened to 70, 80, or even 100, moderate in volume and in force. There is great depression of muscular force; the animal stands limp, as if excessively fatigued. There is diminution, or in some cases total loss, of sensibility of the skin, so that it may be pricked or handled without attracting the attention of the animal. On movement, the horse staggers and shows a want of coordination of all the muscles of its limbs. The senses of hearing, sight, and taste are diminished, if not entirely destroyed. The visible mucous membranes (as the conjunctiva), from which it received the name pinkeye, and the mouth, and the natural openings become of a deep saffron, ocher, or violet-red color. This latter is especially noticeable on the rim of the gums and is a condition not found in any other disease, so that it is an almost diagnostic symptom. In some outbreaks there is much more swelling of the lids and weeping from the eyes than in others. If the animal is bled at this period the blood is found more coagulable than normal, but at a later period it becomes of a dark color and less coagulable. There is great diminution or total loss of appetite, with an excessive thirst, but in many cases cold-blooded horses may retain a certain amount of appetite, eating slowly at hay, oats, or other feed. There is some irritation of the mucous membrane of the respiratory tract, as shown by discharge of mucus from the nose, and by cough. Pregnant mares are liable to abort.

We have, following the fever, a tumefaction, or edema, of the subcutaneous tissues at the fetlocks, of the under surface of the belly, and of the sheath of the penis, which may be excessive. The infiltration is noninflammatory in character and produces an insensibility of the skin like the excessive stocking which we see in debilitated animals after exposure to cold. In ordinary cases the temperature has reached its maximum of 105 deg. or 106 deg. F. in from 24 to 48 hours from the origin of the fever. It remains stationary for a period of from 3 to 4 days without so much variation between morning and evening temperature as we have in pneumonia or other serious diseases of the lungs. At the termination of the specific course of the disease, which is generally from 6 to 10 days, the fever abates, the swelling of the legs and under surface of belly diminishes, the appetite returns, the strength is rapidly regained, the mucous membranes lose their yellowish color, which they attain so rapidly at the commencement of the disease, and the animal convalesces promptly to its ordinary good condition and health, and rapidly regains the large amount of weight which it lost in the early part of the disease, a loss which frequently reaches 30, 50, or even 75 pounds each 24 hours. For the first three days of the high temperature there is a great tendency to constipation, which should be avoided if possible by the use of the means recommended below, for, if it has been marked, it may be followed by a troublesome diarrhea.

_Terminations._--The terminations of simple influenza may be death by extreme fever, with failure of the heart's action; from excessive coma, due generally to a rapid congestion of the brain; to the poisonous effects of the debris of the disintegrated blood corpuscles and the toxin of the disease; to an asphyxia, following congestion of the lungs; or the disease terminates by subsidence of the fever, return of the appetite and nutritive functions of the organs, and rapid convalescence; or, in an unfortunately large number of cases, the course of the disease is complicated by local inflammatory troubles, whose gravity is greater in influenza than it is when they occur as sporadic diseases.

_Complications._--The complications are congestions, followed by inflammatory phenomena in the various organs of the body, but they are most commonly located in the intestines, lungs, brain, or vascular laminae of the feet. Atmospheric influence or other surrounding influences of unknown quality seem to be an important factor in the determination of the local lesions. At certain seasons of the year, and in certain epizootics, we find 40 and 50 per cent or even a greater percentage of the cases rendered more serious by complication of the intestines; at other seasons of the year, or in other epizootics, we find the same percentage of cases complicated by inflammation of the lungs, while at the same time a small percentage of them are complicated by troubles of the other organs; inflammatory changes of the brain, of the laminae, more rarely commence in epizootic form, but are to be found in a certain small percentage of cases in all epizootics.

Exciting causes are important factors in complicating individual cases of influenza, or in localizing special lesions, during either enzootics or epizootics. These exciting or determining causes act much as they would in sporadic inflammatory diseases, but in this case we find the animal much more susceptible and predisposed to be acted upon than ordinary healthy animals. With a temperature already elevated, with the heart's action driving the blood in increased quantity into the distended blood vessels, which become dilated and lose their contractility, with a congestion of all the vascular organs already established, it takes but little additional irritation to carry the congestion one step further and produce inflammation.