Lesions. These vary as do the symptoms. The nasal pharyngeal, and laryngeal mucosæ show congestion, swelling, infiltration, ecchymosis with vesicles, pustules and ulcerations. They are covered by a foul muco-purulent exudate. The same condition may often be traced to the final ramifications of the bronchial system. In pulmonary cases, the lungs show inflammation, inflammatory exudation and consolidation, collapse, splenization, œdema, and even suppuration in points or large areas. The bronchial lymph glands and often the pharyngeal are enlarged, congested and may be suppurating. The pleura over the congested lung may be the seat of exudation and false membrane, and a bloody serum may occupy the pleural cavity. The heart may show parenchymatous degeneration.
In the digestive organs there may be buccal congestion, with degeneration and the desquamation of the epithelium and formation of more or less extended ulceration. The stomach shows similar congestions and degenerations, the ulcer appearing particularly on the summit of the folds. Together with the intestines this often presents numerous petechiæ and ulcerations, and is covered by a foul but often tenacious mucus. The agminated and solitary glands are usually swollen and infiltrated, and the mesenteric glands are swollen, congested and infiltrated.
The kidneys are often congested, and show points of blood extravasation and tissue degeneration.
The meninges of the brain and cord are often inflamed with infiltrations, false membranes, and especially exudation into the subarachnoid and ventricles. Centres of congestion and softening have been noted in the brain and cord with embolism of capillaries and softening and degeneration of their endothelium. Nocard and others have noted a leucocytic infiltration of the perivascular lymph spaces. In old standing cases sclerosis is an occasional feature.
In nearly all cases there is marked emaciation and a very heavy offensive odor comes from the skin, the tissues, the contents of the bowels and the exudates on the respiratory passages.
Lignieres alleges that in the early stages, the specific bacillus is found in the blood and viscera, but that later it is only exceptionally found and that other bacteria (streptococcus, etc.,) usually take its place. In the nasal discharge it may be found at times, but in the more tardily appearing cutaneous vesicles its absence is the rule, and in the brain matter and meningeal and ventricular fluids, in cases of paralysis or chorea, it is not to be detected by culture. Hence the case cannot always be diagnosed by a successful search for, or culture of the germ, and hence also the frequently unsuccessful inoculations with the blood, tears, liquid of vesicles, and even the lung tissues or nasal discharges.
Prevention. Distemper, like any other contagious malady may be excluded from a city or district by the simple expedient of shutting out animals that bear the infection. From a kennel or pack of hounds, new arrivals should be quarantined for a fortnight, until danger is past, and should only be admitted after a good soapy wash. All clothing, collars, brushes and other material that came with them should be thoroughly disinfected. Dog shows and other meetings are to be avoided as far as possible, and any animal that has returned from one should be quarantined and all his belongings purified. Dogs that run at large should be carefully excluded from kennels where valuable dogs are kept, and from all possible contact with them. Even mice, rats, and birds have to be considered if the disease exists in the near vicinity. When the disease exists in a district a sound sanitation would demand the shutting up of all dogs on their owner’s premises, unless carefully led on chain and prevented from coming in contact with other dogs.
When the disease has broken out in a pack of hounds, or a populous kennel, the dogs should be separated into small lots of 3 or 4; the temperatures of all should be taken twice a day; any lot in which one shows a high temperature should be instantly removed to a safe distance and placed in quarantine; and the enclosure where they have been and all their belongings should be thoroughly disinfected. The enclosures where the sick are kept must be carefully quarantined so that no infection may escape on food, water, brushes, utensils, clothing, attendants, cats, vermin, or even birds.
The dogs that are still healthy should have spacious, well-aired dwellings, open air exercise (as much as possible in the fine season), good but not too stimulating food (in part at least fresh animal food), pure water, and protection against undue fatigue, cold, icy baths, especially when exhausted, rain or snow storms and cold stone or metallic beds. In the cold season artificial heat in the kennel is desirable.
Immunization may be sought in various ways based on the use of the toxins and antitoxins on the one hand, and of a weakened type of virus on the other. Bryce (1882) and others inoculated with the blood and pulmonary exudate, and produced in three-months-puppies, local swellings mainly, with subsequent immunity. The mortality from the inoculation did not exceed 10 to 15 per cent. These losses imply that in certain cases the material inoculated conveyed the microbe of the disease, and the survivors acquired all that immunity which comes from a first attack. In the cases that show local lesions only, it may be presumed that few microbes or none were inserted, while the results came mainly from the toxins or antitoxins. This would be entirely in keeping with Lignieres’ observation that the blood and pulmonary lesions often failed to furnish the pathogenic microbe, as tested even by attempts at artificial cultures. The protection secured from the antitoxins alone is shortlived, terminating with the elimination of these elements, while that coming from the action of the toxins on the leucocytes, and the stimulation by these to the production of defensive products, is much more lasting and in ratio with the quantity of the stimulus introduced and the profundity and duration of its influence on the leucocytes. This may partly explain the occasional early exhaustion of the immunity and the reinfection of the animal within a year after inoculation.