ERADICATION OF PULLORUIM DISEASE 1931-32 67 



Group II as in Group I. Only 2.93 per cent of the total tests (209) disagreed, 

 and these were confined to 3 birds with low titered sera. 



It is probable that the percentage of disagreement between the results of the 

 two methods could be reduced if the technique of the whole blood test were 

 more refined. According to these limited observations, it appears that the 

 dilution factor cannot be disregarded, since the thickness of the blood smear 

 cannot be kept uniform, and the amount of antigen coming in contact with 

 blood cannot be kept constant. These factors suggest an inconstant dilution 

 which might be partly responsible for these variations. Also, temperatures 

 near or below freezing in the poultry house at times appeared to have an un- 

 favorable influence on the agglutination reaction. 



The total number of tests made with both methods in the three flocks was 

 2,095. Ten tests included in this total were not classified. Of the remainder, 

 69 were positive, and 2,749 were negative by both methods; 17 were either doubt- 

 ful to both methods or doubtful to one method and positive to the other; and 

 60 were negative to one method and either doubtful or positive to the other. 



Of the birds represented in the latter two groups, 36 were necropsied. The 

 following data show the number of necropsied birds classified as to their reactions 

 to both methods at time of necropsy and the isolation of 5. pullorum. 



S. pullorum S. pullorum 



Isolated not Isolated 



Positive to both tests 7 3 



Negative to both tests 3 15 



Doubtful to both tests 1 



Negative to W.B.T. and doubtful to tube test 3 1 



Negative to W.B.T. and positive to tube test 2 



Positive to W.B.T. and negative to tube test 1 



15 21 



5. pullorum was isolated from 15 of the 36 birds necropsied. Of this number, 

 3 were negative to both methods at the time of necropsy and 5 were negative to 

 the whole blood method and either doubtful or positive to the tube method. 

 The following birds, from which 5. pullorum was isolated, did not react at any 

 time to the whole blood test: 11853, 24854, 71596, 80278, 80328, and 80439. 

 All but one of these birds possessed low titers. 



5. pullorum was not isolated from 21 birds. Of this number, 9 at no time 

 reacted to the tube method but did react to the whole blood method; 8 birds 

 reacted to the tube method, but at no time reacted to the whole blood method. 



While both testing methods failed to detect all infected birds, it appears that 

 the whole blood test is less efficient than the tube test, as conducted in these 

 investigations. The fact that the majority of disagreements between the two 

 methods occurred with birds possessing low titers, suggests that a test is required 

 in which the dilution can be fixed and maintained at a level which will detect 

 such birds. The fact must be recognized that birds with low and fluctuating titers 

 exist, and that when such birds are not detected in a testing program, failure in 

 eradication may be anticipated. 



Since the agglutination phenomenon is in reality the same for both methods, 

 it appears that such a test as the whole blood test should not be expected to 

 give reliable results when all steps in the technique do not remain constant. 

 Investigations and comparative tests have shown that the degree of efficiency 

 of the tube agglutination method was raised when the diff'erent phases in the 

 technique were standardized and made uniform. It is possible that the degree 

 of efficiency of the whole blood method might likewise be raised. 



