The mortality varies greatly. In country dogs it may be below 20 per cent., whereas in city dogs and those kept confined in close quarters and in large numbers it may rise to 50, 60 or even 70 per cent.
Prognosis is especially unfavorable in severe cases; in those profoundly affecting the brain, lungs or liver; in high bred or pampered dogs; in the very young; in the debilitated, anæmic or rhachitic; in those that have been recently imported from another climate and are as yet unacclimated. Puppies from debilitated dams, or those raised in a large litter with insufficient nourishment, or older dogs confined to a purely vegetable diet show less power of recuperation. Profound prostration and offensive odor, from excess of toxins are always to be dreaded.
Incubation in inoculated cases varies from four to seven days (Krajewski). When contracted by simple exposure it may seem to have been extended to fourteen or even eighteen days.
Symptoms. The earliest symptom is hyperthermia (103° to 104° F.) This is accompanied and followed by prostration, dulness, impaired appetite, erection of the hairs along the spine, shivering, trembling, seeking a warm place, fatigue on slight exertion, hot dry nose, burning pads of the feet, sometimes taciturnity. Later the temperature may descend even to the normal or there may be alternations of rise and fall. One of the most characteristic symptoms of distemper is the implication of more than one set of organs, so that morbid manifestations referable to the nose, eyes, throat, stomach, skin and nervous system occurring in the same subject are to be especially noted. In enumerating the prominent symptoms caused by disease of one set of organs therefore, it is not to be implied that the absence of others referring to a different class of organs is to be understood. On the contrary a complication of several is especially significant of this disease, though the predominance in one class of organ will signify a special form of the disease.
Respiratory Symptoms. One of the earliest symptoms is usually sneezing with redness of the nasal mucosa, followed by a muco-purulent blocking of the nose, and rubbing of it with the paws. With the implication of the throat there is usually local tenderness and a hard, painful cough, which may be accompanied by retching or vomiting. The breathing becomes snuffling, especially in pugs and bull dogs, and rapid and even oppressed in case of implication of the smaller bronchia and lungs. The nostrils may become glued together, the discharge red or dark in color, vesicles and sores may appear on the mucosa, and the cough gets paroxysmal, small, weak and husky or gurgling.
Percussion of the lungs may reveal small areas of flatness from exudate or collapse, and in case of pleurisy and hydrothorax there is a lack of resonance up to a given horizontal line, varying in position according to the position of the animal and always keeping to that part of the thorax which may at the time be lowest. Auscultation will reveal various sounds according to existing lesions. There may be a loud blowing murmur over the large bronchia, or at points to which this sound is conveyed through consolidated lung. Or a coarse or fine mucous râle may be present indicating the second stage of bronchitis, or a line of crepitation, around a non-resonant area indicating pneumonia, or there may be friction sounds or, later, creaking murmurs from false membranes. Wheezing and sibilant sounds are not uncommon, also sounds of the heart, bronchia or bowels, heard in unwonted situations to which they are conveyed through consolidated lung tissue. Dyspnœa may become extreme, with puffing out of the cheeks, labial soufle, and violent inspiratory action. Fœtor of the breath is common. Emaciation, marasmus, sunken, pale or dark red eyes, putrid diarrhœa and nervous disorders usually precede death.
Eye Symptoms. Conjunctival congestion is one of the earliest and most constant symptoms. Weeping, swollen eyelids and red turgid mucosa. Photophobia may bespeak keratitis. Soon the watery tears become muco-purulent, matting together the lashes and even the lids, during the night especially, so that they must be sponged to get them apart in the morning. The exudate may accumulate under the lower lid, or may become flocculent, and usually flows down the cheeks causing matting and even shedding of the hair. Vesicles exceptionally appear on the conjunctiva; more frequently it becomes cloudy and opaque, and at points near the centre, degeneration of the epithelium leads to the formation of ulcers no larger than pinheads, but extending into the cornea and sometimes perforating it so as to allow protrusion of the membrane of Descemet or the escape of the aqueous humor. The formation and extension of the ulcers are favored by the general debility, the rubbing of the eye with the paws, and the infection of abrasions, by pus microbes. This infection may extend to the lining member of the anterior chamber and even of the posterior with panophthalmia, but, in the absence of perforation, internal ophthalmia is rare. When the ulcers heal, white cicatricial spots, or black points caused by the adhesion of the uveal pigment remain.
Digestive and Hepatic Symptoms. Anorexia and vomiting may usher in the disease. Buccal congestion, dryness, clamminess and fœtor are marked symptoms and there may be some yellowness of the mouth and eye. The patient is at first costive, but diarrhœa often sets in early, with tenesmus, much fœtor, mucus, froth and even blood, also abdominal pain and tenderness. The abdomen is habitually tense and contracted. The alvine flux may rapidly exhaust the animal, or it may continue for a month in dysenteric form with intense fœtor, weakness, emaciation and exhaustion. Ulceration of the mouth, gums and rectum, invagination, prolapsus ani, jaundice, septic pneumonia, paralysis, chorea, convulsions, or cutaneous eruptions are occasional complications. The abdominal type of distemper is especially fatal. Even in its early stages debility, prostration and even drowsiness are marked features.
Cutaneous Symptoms. Skin eruptions are observed in the great majority of cases, at some stage of the disease, and may remain as a sequel for a time after apparent recovery. Friedberger and Fröhner note cases in which the high fever and skin eruption are the only prominent symptoms, and recovery may be looked for with some confidence. The lesions are most patent on white skinned dogs with short hair, and on the more delicate parts of the skin (abdomen, scrotum, perineum, inside of the thighs and elbows) but they may extend over the whole body and even extend on the mucosæ. They vary much in different cases and stages. There may be punctiform reddish spots, changing to hard elevated papules, and, in the case of a certain number, to vesicles and even pustules. Some vesicles may be small and pointed, but more commonly they are rounded and flat, and as large as a lentil or small pea. When first formed, the contained liquid exudate may be clear and transparent, but often it is reddish or even violet. The individual vesicles tend to speedily burst, and dry up, but others appear, and thus the eruption will continue for weeks, the skin meanwhile exuding a sticky, greasy, offensively smelling exudate which mats the hairs together. Itching is usually slight, yet in given cases excoriations and sores are produced with considerable moist discharge. It tends to spontaneous recovery when the general health improves and appears to be little affected by local treatment.
Nervous symptoms. These are shown more or less from the beginning. The great dulness, depression, apathy and weakness, which usually usher in the disease, are indications of this. Drowsiness may be early shown. Even the early nausea and vomiting may be largely central in its origin. In some cases, however, the brain symptoms are more active and violent. The dog is restless and irritable, getting up and moving from place to place, starting from sleep, yelping, snapping, with twitching of the muscles of the face or limbs, rolling of the eyes, and excessive heat of the head. Krajewski even describes rabiform paroxysms, depraved appetite, spasms, furious delirium, fawning, or threatening, and finally paraplegia and maxillary paralysis Occurring in a country where rabies is familiar it would have been more satisfactory if inoculations had been made from such cases with results negativing rabies. Epileptic attacks may appear at any stage of the disease. Chorea, tonic spasms, paresis and paralysis are on the contrary habitually late manifestations and often seem to be sequelæ determined by toxin poisoning of the nerve centers, or degenerations of their structure. Choreic movements may be confined to the head, or a limb, or they may affect the whole body. Tonic spasms often affect the neck, turning the head rigidly to one side. Among other nervous disorders may be named, amaurosis with dilated pupil and atrophy of the optic nerve, deafness, anosmia, and dementia.