386 Strangles. 



1. Active Immunization. At first experiments were made 

 with living cultures of the strangles streptococcus, but inasmuch 

 as this procedure proved dangerous, dead cultures have recently 

 been used for this purpose. As a matter of fact however there 

 is at present no immunization method at our command which 

 has been tried out sufficiently in practice. 



After the discovery of the strangles streptococcus, Jensen & Sand observed that 

 intravenous injections of pure cultures do not produce strangles, but only an inflam- 

 mation of the vein, after the healing of which the horses resist an intranasal in- 

 fection. This method however could not be utilized in practice on account of the 

 severity of the local inflammation. 



Kitt treated two colts which had not been affected with strangles, in the 

 course of two months with repeated intravenous injections of 5-10 cc. of strangles 

 streptococcus serum bouillon cultures killed at 53-55 degrees, and found later 

 that these animals resisted an artificial infection through the nasal cavities and in- 

 testinal canal. 



Gabritschewsky used a bouillon culture concentrated to 1/10 of its volume, 

 and killed with 0.5% carbolic acid, of which he injected subcutaneously six colts 

 with 60 cc, in 1, 2, or 3 injections. The animals resisted an infection from rub- 

 bing a virulent culture on the nasal mucous membrane, and displayed also a higher 

 resistance against subcutaneous injections of 1.5-2 cc. of virulent culture than did 

 the control animals. Cultures of virulent streptococci also killed by 0.5% carbolic 

 acid but not concentrated, are according to Umeno used in Japan against strangles 

 of horses which is prevalent there. 



Baruchello used as vaccine a mixture of dense streptococci culture, and pleural 

 exudate (aggressin) of artificially infected horses or donkeys (1:8) which had 

 been previously sterilized with toluol (37f), and preserved with ether (2%). The 

 results in practice are claimed to have been satisfactory. 



Wiedenmann immunized rabbits by treating them with cultures which had 

 been shaken for dy^ days with 25% uric acid at 37°, and then concentrated by 

 evaporation. Ealdrey recommends vaccine prepared from 24 hour agar or bouillon 

 cultures, according to Wright's method, by washing them off with salt solution, and 

 heating to 60°. These however proved unreliable even in experiments on rabbits. 



Concerning "strangles extract" (shake-extracts of cultures of strangles strep- 

 tococci?) of Jess & Piorkowski, Otto obtained very satisfactory results from 

 their use in his experience with 694 horses. All healthy animals which had been 

 vaccinated by these methods showed no affection with strangles for a period of 

 eight months. 



2. Passive Immunization. Blood serum of horses artifi- 

 cially immunized against streptococcus infections in man, is 

 recently being used more extensively, and this method appears 

 to be giving satisfactory results when utilized against strangles 

 in horses. According to numerous laboratory experiments it 

 is possible to actively immunize animals Avith artificially attenu- 

 ated streptococci, as well as with toxins, and such animals later 

 hyperimmunized with fully virulent material, produce a blood 

 serum which confers a passive immunity upon other animals, 

 but as a rule only against that strain of streptococci with which 

 the serum-producing animals have been treated. Therefore 

 Marmorek injected his horses with various strains of strepto- 

 cocci of man, and the polyvalent serums obtained thereby have 

 also given better results in human medicine. 



Marmorek 's polyvalent anti-streptococcus serum has also 

 been used by French veterinarians (Jacoulet, Drouin and 

 others) against strangles of horses, since this is a disease also 

 produced hj streptococcus infection. However the results were 

 not promising. As these more or less unsatisfactory results 



