Microbiology. The pathogenic factor found in the lesions was an ovoid bacterium, a little larger than that of fowl cholera, motile, non-liquefying, with polar staining, and often showing in short chains of two or three joined end to end. It grows easily and abundantly in all common culture media, even on potato which fails to propagate the cocco-bacillus of Lignieres. This, with its ready transmission from swine to sheep and vice versa, apparently serves to differentiate it from the cocco-bacillus, and the disease from the hæmorrhagic septicæmia of Lignieres.
Pathogenesis. In Galtier’s first observations in Basses Alpes four separate flocks were infected by pigs brought all from one market, and placed in or by the pens of the sheep where they sickened and one in seven died in a few days. Then the mortality began among the sheep and ranged as follows: 1st flock lost 10 in 37: 2d flock 16 in 25: 3d flock 8 in 20: 4th flock 12 in 22. On one farm 10 sheep were sent to a neighbor’s just before the arrival of the sick pigs and escaped, and on another a second flock kept in outlying pens well apart from the home flock kept perfectly sound.
With cultures of the microbe in vitro, he successfully inoculated sheep, goats, dogs, chickens, Guinea pigs, rabbits, and, finally, a calf and an ass. The cultures were inoculated in different cases; intravenously, into the trachea, pleura, lung, and subcutaneous connective tissue, and one goat was infected by ingestion.
Lignieres claims that Galtier must have worked with a complex infection in which his (Lignieres’) cocco-bacillus was an essential constituent. The evidence of this is, however, lacking, and we must recognize that Galtier made cultures which showed the close relationship of his organisms to swine plague, and their lack of complete identity with those of the Lombriz.
Lienaux and Conte had pathogenic results in a limited number of animals only (rabbit, mouse, Guinea pig) illustrating the familiar truth of the variability in the pathogenesis of different specimens of septicæmic bacteria of the colon group.
Symptoms. 1. Acute Form. There is a sudden marked rise of temperature, often to 107° F., with acceleration of pulse and respiration. Sometimes death follows so early as to prevent the observation of other symptoms. If otherwise there supervene marked dulness, prostration, somnolence, anorexia, suspension of rumination, and more or less tympany of the rumen. The patient is found lying down, apart from the flock, indisposed to rise, with deep red, congested, arborescent conjunctiva and other mucous membranes, and petechial spots on these and on the white portions of the skin. The fæces, at first moderately firm and moulded in pellets, marked here and there with lines of mucus, or even blood, become on the second or third day soft, pultaceous, or watery and highly offensive. Parallel with this, emaciation advances with rapid strides. Breathing becomes more hurried, wheezing or snuffling, with a muco-serous, often bloody discharge from the nose, and an infrequent cough. Careful auscultation and percussion will often reveal the blowing or mucous râles, the crepitation or flatness on percussion of broncho-pneumonia. As the disease advances the petechiæ on skin and mucosæ extend, and extensive deep violet areas show especially on the inner sides of the arms and thighs, on the under surface of the tail, on the perineum and under the belly. Abortion is a common result, the lambs coming dead.
Death may occur in six hours, more commonly in two or three days, or even longer, the temperature going down to below normal in the last stages. In case of recovery, convalescence is slow, the animal remaining emaciated and weak, with lung lesions and persistent cough for a length of time. These poor imperfectly recovered animals continue to harbor the microbe and transmit it. Lesions of the liver and other organs, the result of this disease, are found in sheep that have survived the affection and are afterward killed for mutton.
Symptoms: 2. Subacute and Chronic Form. This is seen in mature sheep of two or three years, that have been infected when in the full vigor of life and health, during an open air life and by a limited dose of the virus. The temperature is less elevated, the circulatory and respiratory functions less disturbed, the dulness and prostration only moderate, the interruption of feeding and rumination transient and tympany slight. Cough and nasal discharge are however present and rather persistent, diarrhœa may be manifested, and marked emaciation occurs. There may be congestion of the mucosæ, but petechiæ and extensive bloody discoloration of the mucous membranes or skin are rarely seen. Abortion is not uncommon.
Recoveries are the rule in this type of the disease, though in some cases it will be delayed for weeks and may even then be imperfect.
Lesions. In the acute types of the disease decomposition advances rapidly after death, and the carcass from the first exhales a peculiarly heavy odor. The skin is discolored, the nasal mucosa is the seat of a muco-purulent or sanguinolent discharge, the anus is soiled with liquid fæces, the subcutaneous connective tissue marked by red arborescence and blood-stained areas, or by a gelatinoid exudation, the muscles at times deeply colored and petechiated, the lymph glands, especially the bronchial and mesenteric, are enlarged and congested of a deep red—the color being highest in the cortical zone. In some old standing cases these may have softened and acquired a grayish hue. They are rich in the specific bacterium.