SPECIFIC INFECTIOUS DISEASES PRODUCED BY COCCI 209 



Inoculations upon the nasal mucous membrane frequently fail 

 to infect. Some authors are inclined to believe that the true cause 

 has not been discovered, and that Str. equi is a secondary invader. 

 Age is a predisposing factor: young animals are most commonly 

 infected. Other predisposing causes are fatigue and exposure to 

 cold, hard work, or any other factor that lowers the vitality. 

 Variations in virulence wholly unexplained probably account for 

 the epidemic character of the disease. 



Disease and Lesions Produced. The infection atria are prob- 

 ably the upper air-passages. The disease may be produced in 

 simple or malignant form. A catarrhal discharge, with inflamma- 

 tion of the nasal mucous membranes, is generally first noted, fol- 

 lowed quickly by a swelling of the adjacent lymphatic glands 

 and of the submaxillary and pharyngeal lymph-nodes. These 

 generally develop into abscesses. The infection spreads through 

 the lymph-channels, but generally remains localized in the tissues 

 adjacent to the point of infection. Metastatic infections may 

 occur in practically any of the organs of the body, and in the 

 chronic types of the disease great variations in localization will be 

 found. Fatal termination is rare (0 to 3 per cent.), but some- 

 times occurs, due to septicemia, pyemia, or pneumonia. 



Immunity. Toxins and antitoxins, agglutinins, and bacterio- 

 lysins have not been satisfactorily demonstrated for this organism. 

 Immunity is conferred by an attack of the disease, but is transitory, 

 and the same animal may suffer from the disease a second time. 

 Animals over five years old are quite generally immune. Probably 

 immunity can be best accounted for by increased opsonin con- 

 tent of the blood and consequent stimulation of phagocytosis. 



Immunization by vaccination with living and with dead cultures 

 has not given wholly satisfactory results. Possibly the injec- 

 tion of autogenic cultures may have a protective influence. Todd 

 has prepared a vaccine by growing the organism on blood-serum 

 for twenty-four hours, then large flasks, containing 10 per cent, 

 serum broth, are inoculated and incubated a month. Six per cent, 

 of sterile glycerin is added, and the material concentrated at 

 60 for two days over unslaked lime. The organism is destroyed, 

 and the material evaporated to a thick paste. This is diluted 

 and used as a vaccine. He has reported favorable results. The 



