ERADICATION OF PULLORUM DISEASE 1931-32 57 



"Conceding that there is a possible 10 per cent error in using the dry blood, 

 yet this method is sufficiently accurate for certain conditions. It can be used 

 by poultrymen who do not especially desire a B.W.D.-free flock, but who would 

 like to minimize their losses from B.W.D. The decreased cost of the test appeals 

 to.the flock owner." Durant (29") tested 259 birds with whole blood, rapid serum, 

 and tube methods. Antigen for the whole blood test was furnished by Dr. M. 

 Dorset, United States Bureau of Animal Industry. The author concluded that 

 the tube test was more eflficient than the whole blood and rapid serum methods 

 according to the testing results and necropsy findings in 111 reacting birds. 

 In Finland, Stenius (87) tested 5 poultry flocks, ranging in size from 170 to 349 

 birds, with whole blood and rapid serum tests. He concluded that the rapid 

 serum method was considerably more reliable than the whole blood method. 



Since certain factors such as quality of the antigen, diagnostic dilution or 

 dilutions, and the length of incubation period appear to influence the efficiency 

 of agglutination tests, it must be recognized that as long as such factors vary in 

 the different investigations, varied results may be anticipated. Unfortunately, 

 in some of the investigations referred to, information concerning these factors 

 was lacking. While the results thus far reported show that the whole blood 

 method is not as efficient as the tube method, yet they offer encouragement for 

 further investigation of the newer method. 



In the endeavor to obtain further knowledge concerning the whole blood 

 test, the following investigation was made. This investigation consisted of two 

 parts: the first concerned birds at the laboratory, and the second concerned 

 three commercial poultry flocks. 



Procedure of the Experiment 



Two groups maintained at the laboratory and consisting of 25 and 27 posi- 

 tive reacting birds, respectively, were tested with the whole blood and tube 

 tests. In the majority of instances the birds were tested by both methods on the 

 same day. The test fluid employed for the whole blood test was a stained, pre- 

 served antigen, furnished by Dr. M. Dorset, Bureau of Animal Industry, United 

 States Department of Agriculture. The technique employed was as follows: 

 a small amount of blood was taken from a wing vein incision and placed on a 

 glass plate with a microscopic glass slide. A smear somewhat thicker than that 

 used in microscopical study was made on the glass plate. One drop of test fluid 

 was added to the blood film with a medicine dropper. The plate was tilted 

 slightly upward and downward, which appeared to have a beneficial influence 

 on the agglutination phenomenon. The reaction was recorded approximately 

 two minutes after the antigen was added to the blood smear. 



In the tube test, the sera were tested in dilutions of 1:10, 1:20, and higher, 

 sufficient to determine the titer, 1 cc. of antigen being used for each dilution. 

 The turbidity of the antigen was equal to tube No. 1 of the McFarland nephelom- 

 eter. The period of incubation was 24 hours at 37 ° C. and an additional 18 to 

 24 hours at room temperature. The agglutination reactions were recorded as 

 follows : 



4 — complete agglutination 



3 — incomplete agglutination 



2 — partial agglutination 



1 — slight agglutination 



— no agglutination 



All birds whose sera gave a reaction of 4-3-2, 4-4-1, or higher in the dilutions 

 of 1:10, 1:20, and 1:40 were considered positive. Sera which agglutinated S. 



