ERADICATION OF PULLORUM DISEASE 1931-32 17 



to 0.75-1 on the McFarland nepheloineter scale. The pH was adjusted to approx- 

 imately 8.4. 



Group B consisted of 6 pullets, 3 months of age, which were placed together 

 in a pen. Six eggs, mixed with sufficient mash to make a semi-dry mixture, were 

 fed daily. This ration was supplemented with cracked grain when the egg-mash 

 mixture had been eaten. The group was given 30 daily feedings of 6 eggs. The 

 birds were tested at weekly intervals by the tube agglutination method in dilu- 

 tions of 1:10 and higher. The antigen employed was identical with that used 

 for Group A. 



Results 



In Group A, specific agglutinins were detected in 4 birds (2 hens and 2 pullets), 

 as is shown in Table 5. Two birds attained a maximum titer of 1:2,560. Sera of 

 5 birds produced non-specific agglutination in the lower dilutions. All birds 

 were necropsied approximately one month after the last feeding with the excep- 

 tion of 1 hen. This bird died of a septicemic form of the disease 14 days after 

 the last feeding. In the majority of the birds, cultures were taken for bacterio- 

 logical determination from pericardial fluid, fiver, spleen, ovary, and any sus- 

 picious lesions. S. pullorum was isolated from the 2 hens, including the fatal 

 septicemic case, whose sera agglutinated pullorum antigen. S. pullorum was 

 not isolated from the remaining 10 birds. 



In Group B, 18 days after the first feeding, three sera produced a sfight agglu- 

 tination in the lower dilutions and one had a titer of 1:640. Seven days later, 

 these 4 birds had developed titers of 1:160 or higher. As is shown in Table 5, 

 agglutinins were produced in the blood of all birds. In 2 birds the maximum 

 titer was 1:5,120 and in 1 the titer did not exceed the 1:80 dilution. One bird 

 died from an intestinal obstruction and the septicemic form of the disease 25 

 days after the last feeding. S. pulloru m was recovered on necropsy. The remain- 

 ing five birds were necropsied 47 days after the last feeding and 5. pullorum 

 was recovered from 2. The organisms isolated from the 4 birds in this experiment 

 were identified by morphological, biochemical, tinctorial, and agglutinable 

 characteristics. 



Discussion 



According to these observations, it is evident that fresh, naturally infective 

 eggs are capable of reproducing the disease when fed to hens and pullets. Evidence 

 of the disease was detected in 4 of the 12 birds that received individual feedings. 

 The fact that each bird in this group received 1 egg at each feeding rather than 

 a portion of a composite of eggs may account partly for the smaller number of 

 infected birds when compared with Group B. It is possible that the age of the 

 birds and the manner of confinement may be responsible for this difi"erence. The 

 incidence of the organism in the eggs may have been greater in those fed to Group 

 B. Since the smallest number of infective eggs necessary to infect birds by the 

 oral route has not been determined, it appears possible that under a suitable 

 environment 1 fresh infective egg might be capable of reproducing the disease 

 in mature as well as immature birds. If such is the case, then the problem of 

 "egg-eating" is of serious consequence in pullorum disease dissemination, because 

 eggs laid on the floor and dropping boards frequently are broken and eaten by 

 non-infected birds. Of course, not all eggs harbor the organism, but it is Mkely 

 that some infected birds may lay infective eggs in places other than nests. This 

 means of dissemination can be eliminated to a large extent by testing young birds 

 before they reach sexual maturity. In spite of the fact that all infected birds 

 may not be eliminated at this age, testing at this time does permit one to dispose 

 of the bulk of the potential source of infection. 



