ERADICATION OF PULLORUM DISEASE 1931-32 47 



the suggestive lesions at necropsy. The tube agglutination test did not show 

 agglutinins to be present in the 10 chicks from which 5. pullorum was isolated. 

 The 1 chick whose serum contained agglutinins, but not in sufficient amount to 

 bring about complete agglutination, was negative to bacteriological examination. 



Among a larger number, 93, of artificially exposed chicks destroyed at the 

 same ages as those of the miscellaneous groups, the serum of only 1 chick con- 

 tained agglutinins. Again the agglutinins were not present in sufficient amount 

 to cause complete agglutination of the antigen, and the chick was negative to 

 bacteriological examination. Whole blood agglutination tests, made on 43 chicks, 

 were negative. Upon bacteriological examination 5. pullorum was isolated from 

 60 of these 93 chicks. 



In two hatches from a flock of reacting hens, the tube agglutination test 

 showed agglutinins to be present in varying titers in the sera of 9 of the 16 chicks 

 killed at 7 days of age, and in 2 of the 19 chicks killed at 14 days of age. Among 

 the chicks which reacted, S. pullorum was isolated from 6 of the 9 and from 1 

 of the 2. S. pullorum was also isolated from 5 of the 7 and from 7 of the 17 chicks 

 which did not react. Agglutinins were detected by the whole blood agglutina- 

 tion test in 4 of the 9 and in 1 of the 2 chicks which reacted to the tube agglu- 

 tination test. No reactions were noted by the whole blood method in chicks 

 that were negative to the tube test. 



Observations based upon these relatively small numbers of chicks in the three 

 groups appear to indicate that specific agglutinins are present in only a small 

 number of chicks which harbor S. pullorum before the age of 2 or 3 weeks. Speci- 

 fic agglutinins sufficient to bring about complete agglutination appeared as early 

 as the seventh and fourteenth days in a few chicks from reacting hens. However, 

 the number of chicks which were found to be bacteriologically positive was 

 larger than the number which reacted to the agglutination test. There appeared 

 to be no relation between the presence of agglutinins in the sera and the demon- 

 strable presence of 5. pullorum organisms in chicks less than 3 weeks of age. 



In the 52 chicks of Part IV, which had been exposed to artificial infection 

 the suggestive clinical symptoms and lesions were confirmed by bacteriological 

 examination in a majority of cases. Agglutinins were present in a few chicks at 

 the time of the first test, i.e., at 4 weeks of age. Agglutinins continued to appear 

 in other chicks up to the end of the eleventh week, but not thereafter. Between 

 the fourth and the eleventh weeks of age, 24 reactors were detected among the 

 32 chicks tested. It appeared that agglutinins required variable periods of time 

 for development. Marked lowering of the agglutination titers occurred in some 

 instances and suggests an ability on the part of some infected chicks to over- 

 come S. pullorum infection. Agglutinins did not disappear entirely from the 

 sera of the 8 reacting pullets. S. pullorum was not isolated from the 3 pullets which 

 had the lowest agglutination titers at the time they were destroyed. These 3 

 came into production earlier than those pullets from which the organism was 

 isolated. It is also noted that S. pullorum was isolated from 3 pullets which 

 failed to come into production. 



During a period of 2 weeks following artificial exposure, no suggestive symp- 

 toms appeared among a group of 75 chicks. Bacteriological examinations showed 

 S. pullorum to be present in 13 of the 50 chicks (Group A) subjected to one ex- 

 posure and in 6 of the 24 chicks (Group A-1) subjected to two exposures. In 

 both groups there were a few chicks whose sera contained S. pullorum agglutinins 

 as early as the fourth week of age. In Group A all of the reactors, 16 in number, 

 were detected by the end of the ninth week of age. In Group A-1 there were 

 12 reactors and 11 of these were detected by the end of the ninth week. The ad- 

 ditional reactor in the latter group was detected at the test at the time of necropsy, 

 at 9 months of age, although on some of the earlier tests this pullet had been 



