CHRONIC INFECTIOUS DISEASES lOB 



Etiology. — A small acid-fast bacillus is constantly 

 present in the lesions, and it is thought to be the 

 cause of the disease. Bang has demonstrated that the 

 disease is contagious. 



Tuberculin Test. — Tuberculin prepared from the 

 avian type of the tubercle gives a positive reaction 

 when injected into animals suffering from Johne's 

 disease, and is therefore used as a diagnostic agent. 

 Bovine tuberculin does not give a reaction. 



Glanders (Farcy). — Glanders is a contagious, in- 

 fectious, and usually chronic disease of equines ; it is 

 communicable to man, in whom the disease is 

 generally acute. 



Etiology.— The B. mallei. Recovery from this 

 disease does not give immunity, nor are there any 

 methods known which give artificial immunity. 



Mallein. — This is a substance similar to tuberculin, 

 prepared from the B. mallei, and is used as a diag- 

 nostic agent for glanders. Mallein contains the toxic 

 substance of the glanders bacillus cultivated in a 

 liquid glycerine medium. The following are the 

 methods employed in applying mallein for diagnostic 

 purposes : 



1. Subcutaneous T^s^.— One-half to 1 drachm of 

 mallein is injected subcutaneously in the neck, the 

 site of injection having been previously disinfected. 

 Before injection the temperature of the animal is 

 recorded. The temperature is taken at the ninth, 

 twelfth, fifteenth, and eighteenth hour after injection. 



