THE WHOLE BLOOD TEST FOR PULLORUM DISEASE 3 



mixed on porcelain plates. Readings were made within one to three minutes. 

 Thirty birds were tested with the whole blood and tube methods. The latter 

 method detected 15 negatives, 9 positives, and 6 doubtfuls, while the whole blood 

 test detected 18 negatives and 12 positives. 



Welch (10) observed with the whole blood test that in using dry blood smears 

 a great variation in thickness of the smears existed and the amount of blood tested 

 was difficult to determine. The author calls attention to the fact that factors 

 exist which lead to errors. It was observed that birds with low agglutinating 

 titres might not react to the whole blood method. The author concludes that the 

 whole blood test, in spite of its deficiencies, has a place in certain areas when the 

 use of the tube test seems impractical. 



Durant (3) in a comparative study of the tube, rapid serum, and whole blood 

 tests found that, among 259 birds tested, 94 were positive to the tube method and 

 63 were positive to the whole blood test. In a group of 23 birds that were positive 

 to the tube method alone, 18 exhibited lesions of pullorum disease and 13 yielded 

 S. pullorum. Among 6 birds that were positive to the whole blood test alone, 4 

 showed gross lesions and 5. pullorum was isolated from one. The author suggests 

 that until the rapid test has proved as accurate and dependable as the tube 

 agglutination test, it should not be substituted in campaigns for the eradication 

 of pullorum disease. 



Van Roekel, Bullis, Flint, and Clarke (9) report that the tube test was more 

 sensitive in detecting infected birds than the whole blood test. S. pullorum was 

 isolated from birds that had not reacted at any time to the whole blood test. 

 Attention is called to factors which exert an influence on the efficiency of the 

 whole blood test. It is emphasized that the whole blood test should be perfected 

 by using a dilution which will be effective and constant in detecting infected birds 

 with low or fluctuating titres. 



Barger and Torrey (1) report as follows: — "Using the tube test as an arbitrary 

 standard of perfection in the detection of reactor fowls the whole blood agglutina- 

 tion test has approached an efficiency of nearly 100 percent in the routine testing 

 of farm flocks." Factors such as constant temperature, proper light, suitable 

 equipment to keep out dust, and skill of the operator were regarded as influencing 

 the accuracy of the test. Equal amounts of blood and antigen were placed on a 

 microscopic slide and mixed with a toothpick. The slide was then placed in a 

 specially devised incubator heated by water to maintain a temperature of 25° C. 

 High temperatures were reported to cause rapid evaporation. Frequent rotation 

 of the slides is recommended to hasten agglutination and give a more definite 

 reaction. It is emphasized that partial, flaky, or pseudo-reactions must not be 

 confused with true agglutination. 



Graham, Thorp, and Torrey (4) tested 1369 blood specimens with the whole 

 blood and tube methods. The index of agreement of positives and negatives 

 between the standard tube and the rapid whole blood method was 0.848. The 

 interpretations of the 1369 tests were classified as follows: — 



Whole Blood 



Interpretation Tube Test Test 



Positive 486 520 



Positive and ropy 88 — 



Partial 20 22 



Trace 3 1 



Negative 772 826 



