IMMUNIZATION TESTS WITH GLANDERS VACCINE. 9 



AGGLUTINATION AND COMPLEMENT-FIXATION TESTS. 



In order to study the effect of the immunizing injections on the 

 serum tests, the blood of the horses in this experiment was subjected 

 to the agglutination and complement-fixation tests from the time of 

 the first injection until the conclusion of the work. It was found 

 that the agglutination value of the serum of the vaccinated horses 

 as a rule increased from the third day after the first vaccination and 

 continued to rise for a time. A decrease was again noted from two 

 to four weeks after the last vaccination and appeared practically 

 normal after six weeks to two months. A complement fixation with 

 the sera of the vaccinated horses was obtained from the seventh to 

 the ninth day after the first vaccination and they continued to give 

 positive fixations from two to three months after the last vaccination. 



These negative serological results which followed the positive reac- 

 tions due to the injected vaccine, appeared only in the animals which 

 gave no reaction to the ophthalmic test, while the blood of those vacci- 

 nated horses which gave a positive reaction to the eye test continued 

 to give a positive fixation until they had been destroyed and proved 

 to be affected with the disease. The same condition was observed 

 in the animals which had been artificially infected with glanders. 



The serological results from these investigations appear to have a 

 great significance with reference to the immunity produced by the 

 injection of dead glanders bacilli. The fact that the demonstration 

 of the presence of immune bodies in the vaccinated horses ceased 

 entirely in two or three months from the last vaccination would 

 indicate that after the lapse of such a time the animals have very 

 little or no immunity against the disease. This is further substan- 

 tiated also by the agglutination value of the sera returning to the 

 normal level. As a matter of fact, previous investigations carried 

 out by Dr. Buck, of this laboratory, showed that one or two sub- 

 cutaneous injections of mallein will give a complement fixation which 

 may last from one to two months. The agglutination value of the 

 serum of such animals is also markedly influenced by subcutaneous 

 malleinization. The serum reaction of horses following the sub- 

 cutaneous injections of mallein is given in detail in Table 4. From 

 this it seems that a mallein injection has almost the same action on 

 the production of immune bodies in a horse as killed glanders bacilli. 

 Table 3 indicates the results obtained with the agglutination and com- 

 plement-fixation tests in the animals used in this investigation. 



On August 20 two vaccinated horses and one check animal which 

 gave positive results to the eye test were destroyed, and in all three 

 animals marked pulmonary glanders was observed. Horse No. 105 

 showed the presence of glanders nodules in the lungs in very great 

 numbers, some of which were of the size of a walnut. In the two 

 other cases, while the nodules were very numerous and from their 



