Sporotrichosis (Mycotic Lymphangitis)

By JOHN R. MOHLER, V. M. D., Assistant 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 scrotum. 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 constitutional 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 appetite 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, potassium 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 analogy 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 assault 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 appetite 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 practitioner 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.