THE WHOLE BLOOD TEST FOR PULLORUM DISEASE 



13 



reactors (93546) gave a partial reaction with the whole blood test; but in two 

 check tests with this method, slightly suspicious and negative reactions, res- 

 pectively, were obtained. With the tube test the serum of this bird gave a "4" 

 reaction in the 1:25 dilution and on dilution test revealed a titre of 1:320. This 

 bird was submitted to the laboratory, while the seven reactors to the tube test 

 were placed in quarantine. At the completion of this test the owner was advised 

 to dispose of the small group of birds which had been maintained in quarantine 

 and continued to reveal positive reactors. 



In February the entire flock was retested with the tube test and no reactors 

 were detected. This group of birds was not further tested since it had passed two 

 consecutive negative tests with the tube method. Of the seven suspicious birds 

 detected on the previous test two had been sold and the remaining five were 

 negative. 



Table 6. --Summary of Tests-Flock A. 



Six of the 26 reactors were submitted to the laboratory for further study. The 

 observations for each bird are presented in Table 7. 



In summarizing the testing results for Flock A, it may be stated that the whole 

 blood test detected the majority of infected birds on the first test, but positive 

 reactors continued to appear by the use of this method for four consecutive tests. 

 Whether the whole blood test would have been capable of eliminating all infected 

 birds from the flock by further testing the unit of birds in which reactors con- 

 tinued to appear, remains a question. To what extent the persistence of infection 

 was influenced by the degree of sensitivity of the whole blood test is impossible to 

 determine from the results. Delayed weak reactions, as well as doubtful reactions 

 occurring within the reading time were observed. As may be seen from the 

 agglutination and necropsy results, the reaction with the whole blood test might 

 be very weak or even negative, whereas with the tube test a complete reaction 

 was exhibited in the 1 :25 dilution. Bacteriological examination of such reactors 

 would yield S. pull or um in some instances. Weak or doubtful reactions appeared 

 identical for birds that proved to be either negative or positive on bacteriological 

 examination. Birds exhibiting a low titre with the tube test generally gave a 

 negative, weak or doubtful reaction with the whole blood test. As the serum 

 titre fluctuated within a definite range, the reaction of the latter method might 

 also fluctuate. Birds with high titres usually produced rapid and distinct reactions 

 with the whole blood method, although in one instance bird 93546 reacted in- 

 differently but its serum titre was as great as that of some birds which gave con- 

 sistent strong reactions. The failure to isolate S. pullorum from this bird may be 

 attributed to the examination or to the fact that the infection was of recent 

 origin, and no definite gross foci had been established. 



