Special Report on Diseases of the Horse Part 65

Cases of chronic farcy and glanders, if not destroyed, may live in a depraved condition until the animal dies from general emaciation and anemia, but in the majority of cases, from some sudden exposure to cold, it develops an acute pneumonia or other simple inflammatory trouble which starts the latent disease and the animal has acute glanders.

In the a.s.s, mule, and plethoric horses acute glanders usually terminates by lobular pneumonia. In other cases the general symptoms may subside.

The symptoms of pneumonia gradually disappear, the temperature lowers, the pulse becomes slower, the ulcers heal, leaving small, indurated cicatrices, and the animal may return to apparent health, or may at least be able to do a small amount of work with but a few symptoms of the disease remaining in a chronic form. During the attack of acute glanders the inflammation of the nasal cavities frequently spreads into the sinuses or air cells, which are found in the forehead and in front of the eyes on either side of the face, and causes abscesses of these cavities, which may remain as the only visible symptom of the disease.

An animal which has recovered from a case of acute glanders, like the animals which are affected by chronic glanders and chronic farcy, is liable to be affected with emphysema of the lungs (heaves), and to have a chronic cough. In this condition it may continue for a long period, serving as a dangerous source of contagion, the more so because the slight quant.i.ty of discharge does not serve as a warning to the owner or driver as profuse discharge does in the more acute cases.

At the post-mortem examination of an animal which has been destroyed or has died of glanders we find evidences of the various lesions which we have studied in the symptoms. In addition to this, we find nodules similar to those which we have seen on the exterior throughout the various organs of the body. Nodules may be found in the liver, in the spleen, and in the kidneys. We may find inflammation of the periosteum of the bones, and we have excessive alterations in the marrow in the interior of the bones themselves. Both these conditions during the life of the animal may have been the cause of the lamenesses which were difficult to diagnose.

In one case which came under the observation of the writer, a lame horse was destroyed and found to have a large abscess of the bone of the arm, with old nodules of the lungs. When an animal has died immediately after an attack of a primary, acute case of glanders, we find small V-shaped spots of acute pneumonia in the lungs. If the animal has made an apparent recovery from acute glanders, and in cases of chronic farcy and chronic glanders, no matter how few the external and visible symptoms may have been, there is a deposit of nodules--small, hard, indurated nodes--of new connective tissue to be found in the lungs. When these have existed for some time we may find a deposit of lime salts in them. These indurated nodules retain the virus and their power to give out contagion for almost an indefinite time, and predispose to the causes which we have studied as the common factors in developing a chronic case into an acute case; that is, an inflammatory process wakens their vitality and produces a reinfection of the entire animal. The blood of an animal suffering from chronic glanders and farcy is not virulent and is unaltered, but during the attack of acute glanders, while the animal has fever, the blood becomes virulent and remains so for a few days.

_Treatment._--Almost the entire list of drugs in the pharmacopoeia has been tested in the treatment of glanders. Good hygienic surroundings, good feed, with alteratives and tonics, frequently ameliorate the symptoms, and often do so to such an extent that the animal would pa.s.s the examination of any expert as a perfectly sound animal. While in this case the number of nodules of the lungs, which are invariably there, may be so few as not to cause sufficient disturbance in the respiration as to attract the attention of the examiner, yet they exist, and will remain there almost indefinitely, with the constant possibility of a return of acute symptoms.

It is probable that some horses may recover from glanders if the infection is slight, but it will not do to depend upon this except under the most stringent veterinary supervision. With good care, good feed, good surroundings and little work, an animal affected with glanders may live for months or even years in a state of apparently perfect health, but with the first deprivation of feed, with a few days of severe hard work, with exposure to cold or with the attack of a simple fever or inflammatory trouble from other causes, the latent seeds of the disease break out and develop the trouble again in an acute form.

In several celebrated cases horses which have been affected with glanders have been known to work for years and die from other causes without ever having had the return of symptoms; but allowing that these cases may occur, they are so few and far between, and the danger of infection of glanders to other horses and to the stable attendants is so great, that no animal which has once been affected with the disease should be allowed to live unless repeated mallein tests have shown him to have become free from taint of glanders.

In all civilized countries, with the exception of some of the States in the United States, the laws are most stringent regarding the prompt declaration on the part of the owner and attending veterinarian at the first suspicion of a case of glanders, and they allow indemnity for the animal. When this is done, in all cases the animal is destroyed and the articles with which it has been in contact are thoroughly disinfected.

When the attendants have attempted to hide the presence of the disease in a community, punishment is meted out to the owner, attending veterinarian, or other responsible parties. Several States have pa.s.sed excellent laws in regard to glanders, but these laws are not always carried out with the rigidity with which they should be.

SPOROTRICHOSIS (MYCOTIC LYMPHANGITIS).

By JOHN R. MOHLER, V. M. D., _a.s.sistant Chief, Bureau of Animal Industry_.

This disease has previously been known in this country as epizootic lymphangitis, or pseudo-farcy. It is a chronic, contagious disease, particularly of equines, caused by a specific organism, the _Sporotrichum schenckii_, and characterized by a suppurative inflammation of the subcutaneous lymph vessels and the neighboring lymph glands. Owing to the fact that this affection does not spread as an epizootic and that its causal factor is a fungus, the name sporotrichosis has been suggested.

The disease in man was first described by Schenck and by Beurmann and Gougerot. Carougeau observed its occurrence among horses and mules in Madagascar, while in the United States it was first observed by Pearson in Pennsylvania in 1907, although it is probable that it had existed for many years in various parts of this country. Page and Frothingham were first to recognize its mycotic nature in the United States. More recently Meyer has also made valuable contributions with regard to the existence of this affection. Its presence has been definitely established in Ohio, Iowa, California, and North Dakota, and there is a probability of its existence in Indiana and several Western States.

_Bacteriology._--The sporotrichum is 2 microns thick, cylindrical and segmented, having more or less branching threads, which bear spores at the end. In the pus they occur as slightly ovoid bodies 3 to 5 microns long, which are somewhat pointed toward the poles, have a sharp double contour, and only on artificial cultivation at a temperature of over 18 do they develop into the characteristic spore-carrying threads.

The period of incubation varies greatly, extending from three days to four months, or even longer. In artificial inoculations with pus through wounds in the skin, inflammation and swelling of the lymph vessels may be noticed in ten to sixty days; these vessels show in their course a development of hard nodules, from which abscesses form.

The natural infection without doubt is caused through superficial wounds, such as galls, barbed-wire cuts, or through various stable utensils, harness, bandages, insects, etc. Solipeds are mostly susceptible, but cattle may also be infected.

_Symptoms._--The inflammation of the lymph vessels is usually first observed on the extremities, especially on one or both hind legs; it may also appear on the forelegs, shoulder, or neck, and more rarely on the rump, udder, and s.c.r.o.t.u.m. The lesions, as a rule, develop in the tissue adjacent to the place of inoculation. In the early stages of the disease the lymph vessels appear very hard and thickened, and along their course hard nodules develop, ranging in size from a pea to a hen's egg. Later these nodules soften, burst spontaneously, and discharge a thick, yellowish pus. The surface of the resulting ulcers or abscess cavities soon fills up with exuberant granulations which protrude beyond the surface of the skin, giving it a fungoid appearance. The affected extremities are considerably enlarged, similar to cases of simple lymphangitis. In rare cases the mucous membrane of the nostrils may also become affected, showing yellowish flat elevations and ulcerations, and these may extend by metastasis to internal organs. In cases in which the mucous membrane is affected, the submaxillary lymph gland may also become enlarged and suppurate.

The const.i.tutional symptoms accompanying this disease are not very marked and may be altogether absent. There is usually only a very slight fever, which seldom runs over 102 F. The appet.i.te is not impaired except in the advanced cases.

_Lesions._--The anatomical changes are most marked in the skin and the subcutaneous tissues. They may become 2 to 3 inches thick and indurated as the result of fibrous-tissue formation, owing to the inflammation present. On the baconlike cut surface suppurative areas and granulating sores may be noticed of various sizes, also enlarged lymph vessels filled with clotted lymph mixed with pus. The neighboring lymph glands are usually enlarged and frequently contain suppurating foci. Rarely the internal organs may show metastatic abscesses.

_Diagnosis._--The diagnosis is based on the characteristic appearance of the ulcerations, which show exuberant granulation of a bright red color, inverted edges, and a thick, creamy, glutinous discharge. These manifestations differentiate the disease from glanders, in which the ulcers are craterlike, do contain exuberant granulations, and the discharge is of a viscous, oily character. The submaxillary and other nodes as well as the corded lymphatics in glanders are more firmly attached to the adjacent tissues, and are therefore less movable. In some chronic cases of sporotrichosis, however, the lesions may closely resemble those of farcy, and in these cases the microscopical examination of the pus will disclose the nature of the affection. In the pus the causative organism can be easily seen in the unstained specimen, and is recognized by its size, shape, and highly refractory double outline. Furthermore, the injection of mallein in cases of sporotrichosis will be attended with negative results.

_Treatment._--At the onset of the disease treatment consists in entire extirpation of the nodules, in case the lesions are localized. In cases in which the nodules have formed abscesses, their opening is recommended, followed by the application of the actual cautery or a 1 to 250 solution of bichlorid of mercury. It must be borne in mind that the organism is quite resistant to antiseptics, and the best results will be obtained from the application of a solution of a strong antiseptic following the opening of the lesions. Internally, pota.s.sium iodid is recommended in 2-dram doses, dissolved in drinking water, twice a day.

In the most favorable cases recovery results in from five to seven weeks; as a rule, however, it requires several months.

In order to prevent the spreading of the disease the affected animals should be isolated, the products of the disease should be destroyed, and the stable should be disinfected with very strong liquid disinfectants in consideration of the resistance of the causative organism.

RABIES, HYDROPHOBIA, OR MADNESS.

Rabies is a contagious disease, which is usually transmitted by a bite and by the introduction of a virus contained in the saliva of an affected animal. It may, however, be transmitted in other ways. It is characterized by symptoms of aberration of the nervous system and invariably terminates fatally. It is accompanied with lesions, inflammation, and degeneration in the central nervous system. It is a disease that is most common in the dog, but is transmitted to the horse, either from dogs or from any other animal affected with it. (See also remarks on page 244.) As a disease of the horse it is invariably the result of the bite of a rabid animal, usually a dog.

Perhaps no disease in medicine has been the object of more controversy than rabies. Certain medical men of prominence have even doubted its existence, and many others have claimed for it a spontaneous origin. The experience of ages, however, has shown that contagion can be proved in the great majority of cases, and, by a.n.a.logy with other contagious diseases, we may only believe that the development of one case requires the preexistence of a case from which the virus has been transmitted.

Pasteur has further added to our knowledge of the disease by showing that a virus capable of cultivation exists in the nervous system, especially in the lower part of the brain (medulla oblongata) and in the anterior part of the spinal column. He has further shown that that portion of the nervous system which contains the virus, the exact nature of which has not yet been demonstrated, will retain it for a very long time if kept at a very low temperature or if left surrounded by carbolic acid; but if the nerve matter, which is virulent at first, is exposed to the air and is kept from putrefaction by substances which will absorb the surrounding moisture, it will gradually lose its virulence and become inoffensive in about fifteen days. He has also further shown that the action of a weak virus on an animal will prevent the development of a stronger virus, and from this he has formulated his method of prophylactic treatment. This treatment consists in the successive inoculation of portions of the nerve matter containing the virus from a rabid animal which has been exposed to the atmosphere for thirteen days, ten days, seven days, and four days, until the virulent matter which will produce rabies in any unprotected animal can be inoculated with impunity. A curious result of the experiments of Pasteur is that an animal which has first been inoculated with a virus of full strength can be protected by subsequent inoculations of attenuated virus repeated in doses of increasing strength.

Innumerable attempts have been made to discover the causative agent, and investigators have announced the finding of many of the lower forms of animal and vegetable life as the pathogenic factor. Among the recently described causes, certain protozoanlike bodies found in the ganglionic cells in 1903 by Negri, and termed Negri bodies, are of a very suggestive nature. Negri claims that these bodies are not only specific for rabies, but that they are protozoa and the cause of the disease. His work has been corroborated by investigators in all parts of the scientific world. An examination of the vitality of these bodies will show a striking resemblance to the vitality of an emulsion of the virulent tissue. Thus, they have been found to be quite resistant to external agencies, such as putrefaction, drying, etc., and are about the last portion of the nerve cell to survive the advance of decomposition.

They are also found in more than 96 per cent of the cases of rabies examined, but have not been proved to exist in other diseases.

Valenti states, as his strongest evidence of the protozoan nature of the bodies, that the virus of rabies is neutralized in test tubes by quinin, while no other alkaloid has this property. As a result of the work performed in the New York City Board of Health laboratory, Park claims that Negri bodies are found in animals before the beginning of visible symptoms, and evidence is given that they may be found early enough to account for the infectiousness of the central nervous system. These bodies are now almost universally considered as diagnostic of rabies, and in the pathological laboratory of the Bureau of Animal Industry their detection in the nerve cells of the brain suffices for a diagnosis of rabies without animal inoculations. In case these granular bodies are not found in a suspected animal, the plexiform ganglion is next examined, and should negative results still be obtained, the inoculation of rabbits is then made as a last resort. It is indeed rare that positive results are obtained from the latter method after the first two methods have been negative, but it has occurred occasionally in cases in which the animal had been killed in the early stages of the disease.

_Symptoms._--From the moment of inoculation by the bite of a rabid dog or other rabid animal or by other means, a variable time elapses before the development of any symptoms. This time may be eight days or it may be several months; it is usually about four weeks. The first symptom is an irritation of the original wound. This wound, which may have healed completely, commences to itch until the horse rubs or bites it into a new sore. The horse then becomes irritable and vicious, and it is especially susceptible to moving objects, excessive light, noises, the entrance of an attendant, or any other disturbance will cause the patient to be on the defensive. It apparently sees imaginary objects; the slightest noise is exaggerated into threatening violence; the approach of an attendant or another animal, especially a dog, is interpreted as an a.s.sault and the horse will strike and bite. The violence on the part of the rabid horse is not for a moment to be confounded with the fury of the same animal suffering from meningitis or any other trouble of the brain. But in rabies there is a volition, a premeditated method, in the attacks which the animal will make, which is not found in the other diseases. Between the attacks of fury the animal may become calm for a variable period. The writer attended a case in which, after a violent attack of an hour, the horse was sufficiently calm to be walked 10 miles and only developed violence again an hour after being placed in the new stable. In the period of fury the horse will bite at the reopened original wound; it will rear and attempt to break its halter and fastenings; it will bite at the woodwork and surrounding objects in the stable. If the animal lives long enough it shows paralytic symptoms and falls to the ground, unable to use two or more of its extremities, but in the majority of cases in its excesses of violence it does physical injury to itself. It breaks its jaws in biting at the manger or fractures other bones in throwing itself on the ground and dies of hemorrhage or internal injuries. At times throughout the course of the disease there is an excessive sensibility of the skin which, if irritated by the touch, will bring on attacks of violence.

Throughout the course of the disease the animal may have appet.i.te and desire water, but on attempting to swallow has a spasm of the throat which renders the act impossible. This latter condition, which is common in all rabid animals, has given the disease the name of hydrophobia (fear of water).

In a case under the care of the writer a horse, four weeks after being bitten on the forearm by a rabid dog, developed local irritation in the healed wound and tore it with its teeth into a large ulcer. This was healed by local treatment in 10 days, and the horse was kept under surveillance for more than a month. On the advice of another pract.i.tioner the horse was taken home and put to work; within 3 days it developed violent symptoms and had to be destroyed.

_Diagnosis._--The diagnosis of rabies in the horse is to be made from the various brain troubles to which the animal is subject; first by the history of a previous bite of a rabid animal or inoculation by other means; second, by the evident volition and consciousness on the part of the animal in its attacks, offensive and defensive, on persons, animals, or other disturbing surroundings. The irritation and reopening of the original wound or point of inoculation is a valuable factor in diagnosis. Diagnosis after death may be made by microscopic examination for Negri bodies or by the inoculation of rabbits, as already mentioned.

Recovery from rabies may be considered as a question of the correctness of the original diagnosis. Rabies is always fatal.

_Treatment._--No remedial treatment has ever been successful. All the anodynes and anesthetics, opium, belladonna, bromid of potash, ether, chloroform, etc., have been used without avail. The prophylactic treatment of successive inoculations is being used on human beings, and has experimentally proved efficacious in dogs, but would be impracticable in the horse unless the conditions were quite exceptional.

DOURINE.

By JOHN R. MOHLER, V. M. D., _a.s.sistant Chief, Bureau of Animal Industry_.

Dourine (also known as maladie du cot, equine syphilis, covering disease, breeding paralysis) is a specific infectious disease affecting under normal conditions only the horse and a.s.s, transmitted from animal to animal by the act of copulation, and due to an animal parasite, the _Trypanosoma equiperdum_.

_History._--It is described as having existed as early as 1796 in the Eastern Hemisphere, and was more or less prevalent in several of the European countries, including France, Germany, Austria, and Switzerland, during the first half of the nineteenth century. Its presence was recognized for the first time in the United States in 1886, when an outbreak occurred in Illinois. Since then the existence of the disease has been observed at irregular intervals in numerous other States, including Nebraska, Iowa, Montana, Wyoming, New Mexico, North Dakota, and South Dakota.

_Symptoms._--There are many variations in the symptoms of dourine, and this is particularly true of the disease as it occurs in this country.

Two distinct stages may be noted which vary somewhat from those described in textbooks, but probably no more than could be expected when differences of climatic conditions and methods of handling are taken into consideration.

The first stage chiefly concerns the s.e.xual organs and therefore differs somewhat in the male and female. In the second stage the symptoms indicating an affection of the nervous system are more prominent and are not dependent upon the s.e.x of the animal.

Following a variable period of incubation of from 8 days to 2 months, there is seen in the stallion an irritation and swelling about the p.e.n.i.s and sheath. In a few days small vesicles or blisters may appear on the p.e.n.i.s, which later break, discharging a yellowish, serous fluid and having irregular, raw ulcers. The ulcers show a tendency to heal rapidly, leaving scars which are permanent. There may be more or less continuous dripping from the urethra of a yellowish, serouslike fluid.

Stallions may show great excitement when brought in the vicinity of mares, but service is often impossible because of the fact that a complete erection of the p.e.n.i.s does not occur.

In the mare the first symptoms may be so slight as to be overlooked. The disease, being the result of copulation, usually begins with inflammation of the v.u.l.v.a and v.a.g.i.n.a. There may be a mucopurulent discharge, which may be slight or profuse in quant.i.ty, agglutinating the hairs of the tail. The mare may appear uneasy and urinate frequently.

Vesicles may appear on the external v.u.l.v.a and mucous membrane of the v.u.l.v.a and v.a.g.i.n.a which later rupture and form ulcers. On the dark skin of the external v.u.l.v.a the scars resulting from healing of the ulcers are white, more or less circular in outline, from one-eighth to half an inch in diameter, and pitlike. This depigmentation of the skin about the external genitals is permanent.

Urticarial eruptions or plaques which break out over various parts of the body are a frequent symptom seen in animals of either s.e.x. These are sharply defined and edematous swellings of the skin about the size of a half dollar or may be even larger. The usual locations of these plaques are the croup, belly, and neck.

The intensity of the symptoms mentioned which are significant of the early stage of the disease may vary to a wide extent and in many instances be so mild as to escape the attention of any but the most careful observer. They commonly disappear after a brief period. The apparent recovery, however, is not permanent, for such animals after a period of variable length manifest const.i.tutional or nervous symptoms.

These may not appear for several months or even years. They consist of a general nervous disorder with staggering, swaying gait, especially in the hind limbs. The animal generally becomes emaciated, the abdomen a.s.suming a tucked-up appearance. The first indication of paralysis will be noted in traveling, when the animal fails to pick up one of the hind feet as freely as the other, or both may become affected at the same time, at which time knuckling is a common symptom. Labored breathing is occasionally noted. When the paralysis of the hind limbs starts to appear the disease usually progresses rapidly. The horse goes down, is unable to rise, and dies in a short time from nervous exhaustion. The appet.i.te usually remains good up to the last.

Although a case of dourine may now and then recover, as a rule the disease is present in the latent stage. Bad weather, exposure, insufficient feed, and complicating diseases like influenza, distemper, or in fact any condition which tends to lower the vitality of the animal, may hasten the termination of the disease.

_Diagnosis._--The complement-fixation test furnishes by far the most reliable means of diagnosis and is especially valuable in a chronic affection of this character, when the symptoms manifested are variable and frequently so obscure as to escape observation. This is a laboratory test requiring special facilities and the services of a trained bacteriologist.