Part 41

In solipeds it ranges usually from 20 to 45 days. The extremes stated are 15 days and 20 months.

In cattle it ranges from 14 to 50 days (exceptionally 70 days), in sheep and swine from 14 to 60 days. It has been claimed to have lasted 4 months in swine and 5 months in sheep.

In rabbits subdural inoculation has an incubation of 15 days, shortening in 25 removes to 8 days, and finally to 6.

In man incubation is alleged to be even more varied. The rule is from 14 to 64 days, but it is claimed to have been as short as three days and as long as 1 to 12 years (Chabert). In the human being, however, there is always the danger of the disease caused by simple dread (lyssophobia) and until these protracted cases can be verified by successful inoculation on the lower animals, they must be held as extremely doubtful. The Montpellier cadet has been often quoted who left, a few days after he had been bitten, spent ten years in Holland, then returning to the school and learning for the first time that his fellow cadet, who had been bitten by the same dog, had gone mad, he too became rabid without loss of time. Such cases have often been cured by moral suasion and have been seized upon to corroborate the heresy that there is no such thing as genuine rabies in man.

Any incubation, in man or beast which has exceeded 40 days should be considered as doubtful, until certified by the successful inoculation of rabbits or other small animals. For casual inoculations the incubation rarely varies much from the time embraced between 16 and 30 days. It is abridged by a special receptivity; by an overdose of the poison; by the inoculation of a virus of unusual potency; by the youth of the animal inoculated; by great heat of the weather; by all forms of violent excitement; by rutting; and by the inoculation of the virus on the head and above all on the cerebral meninges. By this last method incubation may be reduced to 6 days.

Symptoms in Dogs. In dogs as in other animals rabies is manifested in two great types: the furious and the dumb or paralytic, which, however, usually succeed each other in fully developed cases. Yet the furious phenomena may be entirely omitted, and again the victim may die in the early furious stage so that the paralytic does not appear. The prominence of one form over the other is to some extent determined by the germ derived from a previous case of the same kind or by the family, temperament and habits, bull dogs and hounds being specially subject to the furious type, and house and pet dogs having rather the paralytic form.

The premonitory symptoms are in the main the same for both types, and as these may enable us to recognize the disease before the period of extreme danger, it is especially important that they should be well understood.

Some marked change in the disposition or habits of the animal is the first obvious variation from health, and in a district or country where rabies exists any such change should be the warrant for instant seclusion of the dog before there is any disposition to bite. The unwonted habit may be of almost any kind. The lively, amiable dog may become suddenly dull, apathetic or taciturn; the quiet, unexcitable dog may become unusually affectionate, fawning and demonstrative, licking the owner’s hands and face and perhaps infecting him before any suspicion is aroused. Sudden capricious changes from fawning to apathy or sullenness, or the opposite, should be dreaded. The noisy dog may become suddenly silent; while the silent dog may take to howling without apparent cause. A great restlessness, watchfulness or nervousness, a tendency to start at the slightest sound, and a disposition to move at frequent intervals in search of an easier position or place to lie in, are most dangerous symptoms. A morbid appetite, with a disposition to pick up and swallow all sorts of nonalimentary objects (straw, thread, cord, paper, pins, nails, coal, marbles, pebbles, cloth, earth, dung or urine), in a mature dog is most suggestive. Searching around, scraping, tearing sticks, clothes and other objects to pieces, licking of smooth cold stone or metal, of his penis, or of the generative organs of a bitch, are often early phenomena. The dog may hide in a dark corner, going to sleep and grumbling or growling when disturbed. He may make night hideous with his howls, baying at the moon. He may stand with a dull, melancholy, hopeless expression of countenance, as if beseeching his master for relief from his nameless suffering. But as yet there is no disposition to bite. The dog still responds to the call of the master, but with dulness and apathy, in marked contrast with his usual prompt, alert and loving response. There may be congestion, itching and irritation in the seat of the bite, and it may be licked, scratched or gnawed until raw, tender or bleeding. An early change in the voice may be noticeable. There is at first a certain hoarseness, which gradually develops into the pathognomonic rabid howl which is quite recognizable at a distance. The dog turns his nose upward, and with open mouth, emits a howl which, at first hoarse and low, rises into a shriller and higher note before completion and which may be repeated several times without closing the mouth. It is not an ordinary howl but rather a cry of distress, and, to the educated ear a grave note of warning. Sometimes the dog is dumb from the start.

Close observation will often detect evidence of mental delusions and hallucinations even at this early stage. The apparently sleeping dog suddenly starts up with an air of suspicion and excitement. His eyes may turn after phantom flies or other objects at which he will presently snap. He moves hither and thither with a curious, inquisitive air, searching in dark corners, or under curtains or articles of furniture for some imaginary object. He may stand in attentive attitude listening to fancied sounds, and then bound in that direction in spite of an obstructing wall or utensil. If recalled to reality by his master’s voice his healthy attitude and affection may be completely though temporarily restored. He may compose himself to rest or sleep, and soon again start a victim to further delusions.

The furious stage is ushered in by a more pronounced manifestation of the above symptoms. The rabid howl is more frequent and characteristic. The insomnia and the restless movements, change of place, searching, scratching or tearing are likely to be more prominent. The delusions and the watching or snapping at phantoms are more marked. The causeless sniffing and scraping may imply disorder of the sense of smell. The exalted hyperæsthesia and reflex excitability is usually a most marked feature, frequently modified by a sinister, inimical or malevolent disposition. Some subjects show evidence of intense itching, most marked perhaps in the seat of the wound; others are abnormally sensitive to currents of cold air; they start at the slightest noise, a flash of light, a touch, or the approach of a stranger. A paroxysm of fury may be caused at once by shaking a stick at the patient, but, above all, by the test of presenting a dog before his eyes. He at once rouses himself and, with flashing eyes, dashes himself on his supposed enemy and bites viciously, but without bark or growl. The sudden and mute attack is pathognomonic. But there may be symptoms suggestive of some hypoæsthesia. A blow from the dog’s master is usually borne in silence. The animal shrinks from the blow but does not yelp nor howl. During a paroxysm he will lacerate his gums or loosen his teeth by biting on a stick or iron bar; he will even seize a red hot bar without shrinking. He will often gnaw his limbs or body so as to expose and even lacerate the muscles, driven by the pruritus, or the insatiable disposition to bite. Yet he has still an instinct of self preservation, retiring from a light, or blazing brand, and seeking to evade the tongs used to seize him.

The eyes assume a remarkable expression. They are often fixed, and at times the pupils are widely dilated allowing the reflection of light from the brilliant tapetum lucidum, resembling flashes of fire, and adding greatly to his ferocious appearance, and the sense of terror that he inspires. The conjunctiva is congested, of a dark red and the general expression of the eye is very striking. The soft, trusting, affectionate eyes may still for a moment meet those of the loved master, but there is in them a dull, hopeless, anxious and suffering expression, which appeals for pity and should be viewed with dread. To others there is likely to be less of the affectionate appeal and more of the sinister, suspicious, resentful and malicious expression. To the stranger, therefore, the eye may be a better guide than even to the owner. Squinting of the eyes and closure of the lids for a few seconds are not uncommon. As the disease advances the dilatation of the pupils is more marked, indicating the paralysis of the optic nerve.

In this stage the disposition to wander is characteristic. The rabid dog leaves his home and wanders off a long distance, say ten or twenty miles, snapping in his travels at man or beast that may irritate him, returns dirty and exhausted, and seeks anew his dark place of seclusion, or he may snap at and bite even his master. To those who come in contact with him at this time the dog is especially dangerous from his extreme irritability though weak and exhausted.

If the wandering rabid dog meets a strange dog he attacks him and bites without growling or barking. If the bitten dog does not yelp nor retaliate, but simply flees, the rabid animal moves on, but if he bites back, or howls, he worries him, rolling him over and biting again but always in silence, in marked contrast with an enraged but healthy dog. If he comes up with a herd of cattle or pigs or a flock of sheep or fowls, the result is similar. If they remain perfectly still they may possibly entirely escape, but if they scamper off with noise as usually happens, he rushes at them and bites one after another, so that in a confined yard or park all may suffer. A man meeting the dog increases his danger by making an outcry, whereas if he remains perfectly quiet he may possibly escape. Bouley says that a canine attendant is, in a sense, a measure of protection to a man, as the rabid dog attacks first the animal of his own species, giving the man a chance to escape.

In his wanderings the rabid dog will swim rivers, having no dread of water, just as at home he will plunge his nose in water though unable to swallow. When abroad in this way he exhausts himself by his paroxysms and may perish in one of them, or he may meet his death from man or animal. He may in his exhausted state seek a dark secluded place where he may remain for a time and renew his travel later, or he may pass into the paralytic condition and gradually sink.

When shut up, and his vagrant disposition curbed, the paroxysms are liable to appear intermittently, a period of torpor and quiet alternating with one of restless movement, searching, scraping, howling, biting of any animals within reach and later of men, beginning with strangers. A paroxysm can usually be roused by shaking a stick at him and always by presenting another dog.

There is sometimes a difficulty in deglutition, the dog acting as if he had a bone in his throat which he was trying to dislodge, and fatal bites have been sustained during well meant attempts to remove the hypothetical bone. This bears a resemblance to the pharyngeal spasms which are such a marked feature in the hydrophobic man. But it is not roused, as in man, by the sight or sound of water. On the contrary, water is sought and often swallowed at first and even, exceptionally, throughout the disease. He may even take his usual food for a time. The bowels are usually torpid, and any fæces passed are black and fœtid. Diarrhœa may set in later.

In the early stages the rabid dog walks or trots like any other dog. It is only when exhausted by wandering, or violent paroxysms, or both, that he droops his head and ears, hangs the tail between the legs, and slouches along with arched back, and unsteady, swaying limbs. The appearance of these last symptoms implies advancing debility and paresis, and the near approach of paraplegia. The symptoms may, however, be temporarily relieved by a period of seclusion and quiet.

In dumb or paralytic rabies the striking peculiarity is the omission of the preliminary furious stage, and the disease merges at once into paralysis after the premonitory symptoms. In these cases the early nervous symptoms tend to prostration, weakness and dulness or even stupor, there is no disposition to escape, but rather to seek seclusion and quiet, there is rarely howling and then only at first, and soon there is paralysis of the masseters and dropping of the lower jaw, and there is neither ability nor desire to bite. From this the paralysis extends to the hind limbs and then to the fore limbs and trunk. In other cases one limb is the first to suffer, followed by the face, limbs and body. The most prominent feature is the widely opened mouth, the flaccid, hanging tongue and drivelling saliva. The buccal mucosa, at first red and moist, becomes bluish, dry and powdery. The eyes are dull, mournful, suffering or altogether without expression and the pupils are usually widely dilated. The hind limbs are usually utterly helpless and often the fore ones as well, the prostration is extreme and the patient lies quiet and helpless until released by death in two or three days.

A third form, known as the lethargic, is a modification of the paralytic. There may be neither delirium nor marked paralysis, there is no drooping maxilla, pendant tongue nor stringy, hanging saliva, but only a profound, nervous prostration and complete apathy. The patient curls himself up in some dark, quiet corner and cannot be roused by coaxing or punishment, by hunger or thirst. In this, as in the dumb rabies, the common test of presenting another dog fails to rouse excitement or paroxysm. If left undisturbed, these patients may live to the tenth or fifteenth day.

Beside the typical forms there are all intermediate grades, inclining more or less toward the furious, or the paralytic or lethargic. Galtier mentions cases that showed aphasia, scarcely any disposition to bite, swaying movements of the body and limbs, muscular incoördination, tucked up, tender abdomen, rolling the body like a barrel, and marked dyspnœa. Others show at first a slight disposition to bite which is quickly checked by a very early paralysis of the masseters. In still others the attempts to bite are still seen after dropping of the jaw, but though still moved, it cannot be completely closed.

In exceptional cases rabid dogs have shown intermissions of apparent soundness extending over eight days (Youatt), two months (Pasteur), or even six months (Perrin). Rare as these are they must apparently be accepted, and must qualify to some extent the trust reposed in immunization.

Diagnosis. The early diagnosis of rabies in the dog is of supreme importance as enabling the owner to destroy or seclude the dangerous animal before he has developed the disposition to bite and to propagate the disease. If the dog himself is known to have been bitten, every premonitory symptom should be carefully looked for and critically studied. Any change in the general habit, unusual liveliness or dulness, restlessness, or somnolence, unwonted affection or taciturnity, special watchfulness with vision, or hearing, change in the character or tones of the voice or the disposition to use it, propensity to swallow foreign nonalimentary bodies, retching, vomiting or costiveness, propensity to hide away in a dark corner or to leave home and disappear for a day or more, disposition to gnaw and tear up wood or clothing, or hyperæsthesia affecting any of the senses should be carefully noted. Note especially any exaggeration of the generative instinct, any strabismus, or redness of the eyes, any turning of the eyes or head after imaginary objects or snapping at them, any disposition to anger or attack when another dog or cat is presented and any disposition to growl at or to bite a stranger. This tendency to anger and resentment though not always present is usually a symptom of the very greatest value. If a dog is known to have bitten or attempted to bite any person or animal he should be tied or shut up in a safe place for four days at least, under veterinary supervision, and set free only on condition that no symptoms have developed at the end of this period. A hasty decision that a suspected dog is not rabid must lay a veterinarian open to the most serious charges, in case rabies occurs in man or beast from the bites.

Diagnosis is less difficult after the paroxysmal stage has set in. Then there is the extreme irritability and hyperæsthesia, the appearance of reflex spasms of the pharyngeal muscles and chest under the influence of any peripheral excitement, the derangement of the senses, the dilated pupil, the flashing eye, the squinting, the taciturnity and the propensity to bite. Later still the lack of coördination of movement or the paralysis, especially of the hind limbs and of the jaws.

The symptoms may be simulated by those of some other diseases. Thus the bitch which has been exhausted by lactation may show delirium with taciturnity and a disposition to snap. The dog, which is habitually struck or threatened by passers by, may acquire a sinister look and a disposition to bite on every occasion. The presence of a bone or other foreign body fixed between the upper molars, and various injuries of the jaws, teeth or throat may cause inability to swallow, change of the voice and a morose disposition and expression. In such cases there may be vomiting, rubbing the jaws with the paws as if to disengage something and salivation, but there is neither delirium, fury, muscular weakness nor paralysis. In paralytic rabies on the other hand, along with the open mouth and drivelling saliva, there is no disposition to paw the mouth nor face, the buccal mucosa is not simply red but of a deep violet, and there is attendant weakness or paralysis of the hind parts.

Galtier has seen inability to swallow and dropping of the lower jaw from violent stomato-pharyngitis, and from dislocation of the maxilla.

Great tenderness of the skin from inflammation due to blistering or caustic agents or from rheumatism may cause such alert apprehension and disposition to bite in self defense that it may simulate hyperæsthesia of rabies.

From pharyngeal anthrax and violent angina, rabies is distinguished by the extreme exaltation of the special senses, the marked hyperæsthesia and reflex excitability, and, as in the other diseases mentioned, by the perfectly lucid intermissions. Epilepsy is not to be roused by sudden noise, movement nor attempts to swallow, it is not associated with hyperæsthesia and in the haut mal the spasms affect the muscular system more generally. A disposition to bite, and spasms and other nervous symptoms, resembling to some extent those of rabies, have been seen in cases of pentastoma in the nasal sinuses, cysticercas in the brain, filaria immitis in the blood, nematodes, and tænia in the bowels, and auricular acariasis, but there is no such hallucination nor visual delusion, no alteration of the voice, no cutaneous anæsthesia, no exalted reflex excitability. Cadeac finds rabiform symptoms with disorders of the special senses in animals dosed with various essential oils, but the odor of these essences about the mouth and in the breath would serve to distinguish.

Symptoms in Cats. The disease makes a rapid progress, and often ends in death in three or four days. There is a marked change of voice, the calls being hoarse and bass, having been compared to that of a cat in heat. As in the dog, there is a disposition to pick up and swallow objects that are in no sense food, perhaps even its own urine or fæces. There is a great tendency to hide away under furniture or in secluded corners so that the malady may be far advanced before anything is suspected. If seen the patient shows restlessness and frequent movement, with a marked excitability under noise or other disturbing influence. Any disturbance may arouse a paroxysm, accompanied by occasional wide dilatation of the pupils, with flashes from the bright carpet in the vitreous chamber, and the patient may spring at human beings and bite or scratch the hands, face or other uncovered portion of the body. It shows the same disposition to bite small animals, and especially dogs. A glairy often frothy saliva is found in the mouth and often around the lips. As the disease advances and paresis sets in, the cat usually crawls into some dark secluded corner and there dies.