The fundamental objection is that it entails the preservation, encrease and spread of the poison, and like all temporizing measures, stands as a barrier to the complete extinction of the plague. Giving such a very transient protection, its repetition may be demanded in a few months or a year, and proceeding on the ground that the pest must continue for all time, the apparent economy of the process will prove, in the long run, but a permanent and grievous tax.
The soundest and only truly economical course in dealing with this and other deadly infections of swine is the radical extinction of the germ. When the people can be educated up to this we shall see the dawn of a brilliant future for our animal industries. Until then we must be satisfied to fall back upon, and make the best use of the temporizing measures now in vogue or that may hereafter be devised. Even if it should be shown that hog cholera is at long intervals developed from a ‘sport’ of the usually harmless bacillus coli commune, the fact remains that its great extensions and the resulting fatality are due to the contagion alone, so that extinction remains the true watchword of success and economy.
SWINE PLAGUE: SEPTICÆMIA HÆMORRHAGICA SUIS.
Definition. Synonym. Bacillus pestis suis, 0.8–1.5μ, nonmotile. Pathogenesis. Accessory causes, as in hog cholera: less vitality than in virus of hog cholera, bacillus in apparently healthy, deadly to birds and rodents. Lesions: like as in hæmorrhagic septicæmia, lungs suffer more than bowels, lymph glands swollen hæmorrhagic, liver and spleen may seem almost normal, bowels slightly congested, marked emaciation. Symptoms: Acute cases like hog cholera, shorter incubation—1 day, troubled breathing when driven, cough, congested petechiated skin, hyperthermia, costiveness followed by diarrhœa. Diagnosis: constancy and predominance of lung lesions and symptoms, nonmotile bacillus with polar staining, not gasogenic with glucose, very fatal to birds and rodents. Prevention: as in hog cholera. Immunization. Treatment: as in hog cholera dangerous. Serum-therapy.
Definition. A contagious bacteridian disease of swine, acute or subacute, characterized by a short incubation, hyperthermia, marked congestion of the mucosæ, petechiæ and circumscribed blood extravasations in the skin, subcutis, mucosæ, submucosæ, and tissues, swelling, congestion and petechiation of the lymph glands, and a marked tendency to inflammatory localization in the lungs.
Synonyms. Th. Smith identifies this affection with the “Schweineseuche” of Germany.
Bacteriology. The bacillus of Swine Plague (B. Pestis Suis) has already been described in the differential table of allied bacteria given under hog cholera. It is a short rod, with rounded ends, 0.8 to 1.5μ. × 0.6 to 0.8μ, staining readily in aqueous basic aniline colors and bleaching in Gram’s iodine solution. The staining is distinctly polar, the colored portions being more or less crescentic with the concave or straight border turned inward toward the central clear space. It is destitute of flagella and distinctly nonmotile unlike the very active bacillus of hog cholera. It further differs in its growth on potato which is slight, gray and waxy. On gelatine, too, it gives a feeble growth (or none) unlike the brownish colonies of the bacillus of hog cholera. It fails to liquefy gelatin. On agar the growth is more active, being grayish, translucent or brown. Those forming under the surface are like flat horizontal discs with a small microscopic elevation or knob in the center. It grows in milk producing little or no acid and no clot. It produces gas with none of the sugars—glucose, lactose, saccharose—in contrast with the gas production in glucose by the hog cholera bacillus. It shows much less vitality and hardihood than the hog cholera bacillus, growing but feebly between 65° and 70° F., and most actively at 97° to 100° F.; dying in 7 minutes at a temperature of 58° (moist); dying in 3 days when dried, in 4 to 6 days in the soil, in 10 to 15 days in water and instantly in 0.04 per cent solution of lime water.
Pathogenesis. It is pathogenic to swine, hens, pigeons, pheasants, sparrow, mice, guinea pigs, rabbits, cattle, deer, etc., showing not only a wider range than the hog cholera bacillus, but a more deadly action outside the genus suis. Inoculated birds die in 2 days, rabbits in 16 to 20 hours and guineapigs in 1 to 4 days.
Accessory Causes. These agree in the main with those of hog cholera already described so that it is needless to repeat them here. The principal distinctions depend on the lesser vitality of the swine plague bacillus outside of the animal body, and its wider range of pathogenesis outside the genus suis. Infecting materials that have been thoroughly dry for a week may be considered harmless, also that which has been more than two weeks in water, and that which has been more than a week in the soil. If, therefore, the buildings have been thoroughly disinfected, the simple disuse of yards and pastures for a fortnight, and of ponds of water for three weeks may suffice. In the case of hog cholera it may be necessary to abandon such places for 5 months or for the season.
Abandonment by swine is, however, insufficient: all susceptible animals, wild and tame, (see pathogenesis) must be excluded as any one of these may maintain the infection. The preservation of recovered swine on the premises, or the early return of the immune may become a means of preserving the bacillus for the next susceptible pigs that may be introduced. The bacillus of swine plague may be found on the air passages of swine and other animals that are not themselves, at the time, susceptible to the disease, and these animals accordingly become the occasions of what have been thought to be spontaneous outbreaks, and of invasions of fresh herds after the introduction of healthy pigs which have been thought to be beyond suspicion. The danger of the communication of the germ by wild birds and rodents would be enormous, but for the fact that it is so much more deadly to these animals than the microbe of hog cholera, that few survive to maintain the infection. Yet the rule ought to be, to exclude from the fields or premises occupied by new or susceptible pigs, all animals, that may by any possibility become the means of introducing the infection so recently prevalent. Though so easily destroyed when outside the living body, the microbe of swine plague can be carried by the apparently healthy living animal and we must rigidly exclude the possibility of this occurring.