208 VETERINARY BACTERIOLOGY 



described the organism now generally considered to be the specific 

 cause. 



Distribution. The disease is quite widely distributed, both 

 in Europe and America. It generally attacks young animals. 



Morphology and Staining Characters. The organism is a gram- 

 positive Streptococcus, resembling the Sir. pyogenes in both mor- 

 phologic and staining characters. Some authors state that the 

 organism is gram-negative, for it is decolorized if the alcohol 

 remains too long in contact. The chains are usually long and 

 twisted. 



Isolation and Cultural Characters. The organism may be 

 isolated in pure culture, in most cases from the deeper portion of 

 the characteristic abscesses, by the same methods used for Sir. 

 pyogenes. No specific differences in cultural characters have been 

 shown. Bureschello claims that in many cases strangles is a 

 mixed infection of Staphylococcus aureus and Streptococcus equi. 

 In such cases plating would be necessary to differentiate the species 

 of organisms present. 



Physiology. A temperature of 60 will destroy the organism 

 in an hour, and 80 in thirty minutes. It is destroyed readily 

 by direct sunlight and by disinfectants. It grows well at room- 

 temperature, although its optimum is blood-heat. 



Pathogenesis. Enough has already been said to make doubt- 

 ful the standing of strangles as a specific disease caused by a 

 specific organism. 



Mechanism of Disease Production. Little is known of the 

 factors that determine the pathogenicity of the organism. Prob- 

 ably they differ little, if at all, from those of Str. pyogenes. 



Experimental Evidence of Pathogenesis. Pus from abscesses 

 in strangles kills white mice, with evidence of acute septicemia 

 in two to four days. An abscess generally develops at the point 

 of inoculation. Rabbits and guinea-pigs succumb to the injection 

 of large quantities of the organism, but are not readily infected. 

 Other animals are very resistant. Subcutaneous inoculations of 

 the horse will usually provoke abscess formation at the point of 

 inoculation. Typical strangles in horses was caused by Schiitz 

 by use of pure cultures. It seems evident, however, that there 

 must be some predisposing factor to the disease in most cases. 



