48 CONTROL SERIES No. 63 



regarded as suspicious. It appears that the tube aggkitination test is capable of 

 detecting the infected chicks, with few exceptions, when the test is appHed to ar- 

 tificially exposed chicks between the ages of 4 and 11 weeks. Lowering of agglu- 

 tination titers even to the point of disappearance occurred in a small number of 

 chicks, and upon failure to isolate 5. pulloriim was regarded as indicative of re- 

 covery from the disease. Again 5. ptdlorum was isolated from the 2 pullets which 

 failed to come into production. 



Conclusions 



1. Although S. pullorum agglutinins sufficient in amount to establish a 

 diagnosis were not present in the sera of 15 chicks from 5 to 19 days of age, 

 5. pullorum was isolated from 10 of the chicks. 



2. S. pullorum agglutinins sufficient in amount to establish a diagnosis 

 were not present in the sera of 93 artificially exposed chicks from 5 to 19 days 

 of age. 5. pulhrum was isolated from 60 of the chicks. 



3. In the sera of some chicks, 7 and 14 days of age, hatched from eggs from 

 reacting hens, 5. pullorum agglutinins were present in sufficient quantity to es- 

 tablish a diagnosis, and 5. pullorum was isolated from some chicks which did not 

 show agglutinins. 



4. In three groups of chicks, all reactors were detected, with one except'on, 

 by the end of the eleventh, ninth, and ninth weeks, respectively. 



5. Some reactors detected between the fourth and ninth weeks of age later 

 became non-reactors, and 5. pullorum was not isolated upon necropsy. 



6. S. pulloriim was isolated from non-reacting chicks up to 8 weeks of age. 



AVENUES OF INFECTION 



Investigations have definitely established the fact that pullorum disease 

 is disseminated among live poultry, including both immature and adult stock. 

 The disease has also been reproduced through artificial means of exposure. 

 Rettger (70) in his first report concerning pullorum disease observed that the 

 malady could be reproduced in young chicks (2 to 4 weeks of age) by subcutaneous 

 inoculation with pure culture of the causative organism. Later Rettger, Kirk- 

 patrick, and Card (79) were successful in producing infection by inoculating the 

 organism into the oviduct. They reported that the male plays an important 

 role in the transmission of the disease from diseased to normal hens according to 

 circumstantial evidence, and that the probability of oviduct infection being 

 brought about in any other way, as for example through infected litter, appears 

 quite remote. Bailing and Allen (20) also demonstrated that the disease could 

 be reproduced in young chicks by subcutaneous inoculation. They found that 

 chicks fed 0.5 cc. of a saline suspension of live culture (one billion organisms per 

 cubic centimeter) would succumb to the disease. Feeding of broth cultures also 

 produced death. They reported that an amount as small as 0.0001 cc. of a sus- 

 pension containing one billion organisms per cubic centimeter produced death 

 in one of the two chicks fed. It was concluded that a correlation existed be- 

 tween the age of the chick and the tolerance for the dose of infective agent. 



Doyle (27) showed that adult fowls could be infected by subcutaneous and 

 intravenous inoculations with broth cultures of the organism. The disease was 

 also reproduced through oral administration and oviduct inoculation of the or- 

 ganism. The organism was pathogenic for chicks when fed or inoculated sub- 

 cutaneously in doses as small as 0.001 cc. Chicks were also infected by instilling 

 into the eye a couple of drops of broth culture. Gwatkin (39) in feeding adults 



