24 CONTROL SERIES No. 63 



Procedure of the Experiment 



Twenty-four Rhode Island Red pullets (9 to 13 weeks of age) that reacted 

 positively to the tube agglutination method were placed in contact with twenty- 

 four Rhode Island Red pullets (8 weeks old) that were purchased from a pullorum 

 disease-free flock and that were negative to the tube agglutination test. The 

 birds were placed in an 8 x 12 foot house and provided with a grass range (size 

 30 X 40 feet). The house and range had not been employed previously for in- 

 fected stock. All birds were tested at weekly intervals with the tube agglutina- 

 tion method in 1:10, 1:20, and higher dilutions. The antigen employed was 

 identical with that used for Investigation No. 3. The positive reacting pullets 

 were removed from the flock when they approached sexual maturity in order to 

 eliminate the possibility of infective material (eggs and degenerated ova) playing 

 a role in dissemination. 



After the sixty-sixth day of the experiment, the birds had access to the 

 range only 2 days a week, due to lack of green grass. A screen porch (8 x 12 feet) 

 was provided for the birds when they did not have access to the range. On the 

 sixty-ninth day one of the non-reacting pullets affected with subcutaneous 

 emphysema was removed from the flock for treatment. This bird was retained 

 in a cage by itself and returned to the flock after being in isolation for a period of 

 3 weeks. 



The positive reacting pullets remained with the flock as follows: 3 for 62 

 days; 2 for 84 days; 3 for 105 days; and the remaining 13 for 111 days. Two 

 positive pullets that revealed symptoms of depression, anorexia, and emaciation 

 were necropsied on the sixty-fourth day. 5. pullorum was isolated from the 

 pericardial fluid, liver, spleen, and peritoneum of 1 of these birds. One positive 

 pullet became paralyzed, was necropsied on the seventy-seventh day, and S. 

 pullorum was not isolated. 



The experiment extended from June 10 to December 28, 1931, inclusive. 

 The non-reacting pullets remained negative for 111 days while in contact with 

 the reactors and for 91 days after the positive birds had been removed. All 

 but 2 of the non-reacting pullets had laid at the end of the experiment. One 

 non-reacting bird was necropsied 21 days after the reactors were removed. 

 Death was due to acute peritonitis caused by foreign material escaping through 

 a perforation in the wall of the proventriculus. 



Table 6 shows the weekly agglutination titers of the reacting pullets during 

 the course of the experiment. The titers of the majority of the birds decreased 

 during the course of the experiment. Thirteen birds had titers of 1 : 160 or higher 

 at the time they were removed from the non-reacting birds. In a few instances, 

 the titers fluctuated markedly during the period of observation. 



Discussion 



According to these findings, ]Jullorum disease did not spread among infected 

 and non-infected sexually immature pullets while maintained in close contact. 

 Whether these observations approximate those which one might find among 

 practical conditions has not been determined. The results indicate that the or- 

 ganism either was not eliminated by the infected birds or not eliminated in 

 sufficient numbers to produce infection in the susceptible birds maintained under 

 the conditions described. The presence of certain factors such as management 

 and sanitation might exert a favorable influence on the spread of the disease. 

 Perhaps the number of birds employed, the duration of the contact, and the 

 post-contact periods might be influencing factors in bringing about transmission 

 of the disease. These resu ts are not regarded as conclusive and this problem is 

 worthy of further consideration. 



