Definition.—A specific infectious disease peculiar to animals, especially the dog, and communicated to man by inoculation, generally by a bite. It is characterized in man by melancholia; great fear of water; violent spasms of the pharynx and larynx, rendering deglutition and respiration very difficult; great prostration, a stage of paralysis, which generally terminates in death.
Etiology.—The specific cause has not yet been determined, though bacteriologists agree that it is microbic in origin, that a toxin is developed which infects the saliva and blood of the victim. This is communicated to man in about ninety per cent of all cases by the bite of a rabid dog.
The presence of saliva, however, on an abraded surface is sufficient to produce the disease. Of domestic animals liable to rabies, the cat, horse, and sheep are next in order, while a number of wild animals are susceptible, and when infected lose their shyness, timid animals becoming bold.
Many persons seem immune, as only about twelve to fifteen per cent of the persons bitten contract the disease. The degree of immunity, however, most likely, is the result of the part bitten. Thus Ballinger states that ninety per cent of all persons bitten in the face contract rabies, while only a small per cent are affected when bitten on covered parts of the body, the virus being wiped off by the intervening clothing.
It is quite rare in the United States, while in Russia it is quite common. The toxin seems to spend its force upon the central nervous system.
Pathology.—The pathological changes found after death are not different from those in some other diseases, hence are not characteristic. Thus we find congestion of the mucous membrane of the pharynx, larynx, trachea, and bronchi, and sometimes of the lungs.
The abdominal viscera is not affected. The blood-vessels of the cerebro-spinal system are congested, and sometimes minute hemorrhages occur. These are most marked in the medulla and upper part of the spinal cord, but may be entirely absent.
Symptoms.—The period of incubation is longer than that of any other known disease, and varies greatly in different cases, usually a shorter time in children than in adults. The intensity of the virus and location of the wound, in all probability, determine to some extent the time of the forming stage. When the injury is large and on the face or head, the toxin does its work more quickly.
From two weeks to three months is the usual period, though it may be prolonged to one year or more. The wound frequently heals as readily from the bite of a rabid dog as from one not affected.
Prodromal symptoms are headache, loss of appetite, and a depression that is somewhat characteristic, the patient being melancholy, with the sense of impending danger. There may be a stinging sensation or itching at the seat of the bite, and the part becomes numb; sometimes the cicatrix becomes red and swollen. These symptoms last from one to three days.
The patient is restless and uneasy, and the slightest noise, a flash of light, a draft of air, or a sudden call, will produce undue excitement; or the patient sits quietly in a despondent mood, with an occasional sigh. As the disease progresses towards the spasmodic or true hydrophobic stage, respiration becomes oppressive and the voice rough, and a seizure may be expected momentarily; this stage lasts from one to three days.
The second stage is characterized by spasmodic contraction of the larynx on attempts at swallowing. The sight of water produces great fear, and often precipitates a spasm which is attended with great suffering; the dyspnea is great, and the convulsive action of the larynx and muscles of the mouth causes the patient to emit guttural sounds, which, to the excited and horror-stricken observer, seem to resemble the bark or howl of a dog. The temperature is usually slightly elevated, from 100° to 103°, though the temperature may be subnormal.
These paroxysms occur at intervals; when the seizure subsides, the mind is perfectly clear, though the patient is greatly exhausted. In extreme cases, the patient is maniacal, and must be prevented from injuring himself or attendant. This stage lasts from one to three days, and gradually passes into the third stage, known as the paralytic stage.
The paroxysms become less violent, the patient being able to swallow with some difficulty, the prostration is great, the heart's action feeble, the skin is relaxed, and the surface is covered with a cold sweat. The mind, which has been clear during the interval of intense suffering, now becomes clouded, and the patient finally passes into coma, the spasms entirely subside, and in from ten to twenty hours the patient expires.
Although the incubating stage may be longer than that of all other diseases, the duration of the disease is, fortunately, very short, from two to four days.
Diagnosis.—After the disease is once fully developed, there is but little difficulty in making a diagnosis. The spasm of the muscles of deglutition and respiration, the intense fear of water, the excitation of the patient on the slightest irritation, are so characteristic that one could scarcely be mistaken.
In tetanus, which slightly resembles rabies, the disease develops in from five to ten days, begins with trismus, and very often is attended with episthotonos.
Pseudo-hydrophobia—lyssophobia—somewhat resembles hydrophobia, but is purely neurotic, and occurs in hysterical individuals.
A person with a vivid imagination and of a highly excitable temperament, after being bitten by a dog, develops, in a few weeks, symptoms that may be misleading. He declares that he can not swallow, grasps his throat, breathes with difficulty, and to all appearance, has the true disease. It will be noticeable, however, that the attacks are not so severe, that the first week passes without the patient growing worse, and that the temperature remains normal.
Prognosis.—The prognosis is always unfavorable.
Treatment.—Prophylaxis.—The surest method would be, the muzzling of all dogs, as has been proven in Prussia, and later in Holland. In the former country hydrophobia was quite common previous to compulsory muzzling, but since its enforcement the disease has been eradicated.
When a patient has been bitten, the wound should at once be treated, and the poison removed by suction or the use of cups, or the injured part excised. Of course the patient would need to be seen very soon after the injury took place. If this course is not followed, then the wound should be thoroughly cauterized with carbolic acid, caustic potassium, or the actual cautery, and the wound kept open for a few weeks.
When the disease is fully developed, the treatment will be for the purpose of relieving the patient's suffering. Inhalations of chloroform and hypodermic injections of morphia are the most efficient means for this purpose. The patient should be placed in a dark room, quiet enjoined, and all visitors forbidden. As a curative measure that needs to be tried, I would suggest large doses of echinacea, as recommended by Dr. Goss. The hypodermic injection of gelsemium is also worthy of trial.
Dr. Pasteur's preventive inoculation, that was expected to do so much for the world, has been a disappointment. Pasteur institutes were established in various parts of the world, and the zeal with which the method was used may account for the increased number of cases of rabies over former years.