ERADICATION OF PULLORUM DISEASE 1930-31 7 



Table 1. — A comparison of the percentages of reactors detected among females and males. 



♦Includes reactors detected on retest. 



Some investigators have observed that infection may spread from an in- 

 fected mature female to a non-infected by contact eitlier in the absence or 

 presence of males. To our knowledge, no observations have been recorded 

 stating that infected males may transmit the disease to fetnales or other 

 males. Since males are found infected (in some cases lesions being comparable 

 to lesions in females), one might assume that they might play a role in direct 

 transmission of the disease. 



The problems of soil and house infection have received very little attention. 

 One investigator reports that the causative organism of the disease may re- 

 main in the soil in a virulent condition for a period of fourteen months. This 

 was true for both red clay loam and rich black loam. In the published report 

 the author did not state definitely whether the soil had been infected artifici- 

 ally or whether it had been contaminated by infected birds; but by personal 

 correspondence it was learned that the soil samples were sterilized and arti- 

 ficially inoculated in crocks. 



Adult birds may become infected by feeding infertile eggs from infected or 

 untested sources. Fresh eggs laid by infected birds and eaten by non-infected 

 birds may be a possible means for the spread of infection among adults. 



AmoiKj chicks. — Eggs from infected birds may contain the organism, and 

 if such eggs are hatched the chicks may be infected. Incubator hatching has 

 played an important role in the dissemination of tlie disease. Investigators 

 have demonstrated conclusively that infection will spread in various types of 

 incubators and to a greater extent in some than in otiiers. The organisms 

 adhere to down and dust particles which are circulated by a movement of 

 air currents. Chicks inhaling these particles may become infected through 

 the respiratory tract. Infection may also gain entrance through the digestive 

 tract, if infective material is picked up. There may he other avenues that 

 have not been discovered definitely, as for example the eye. Attempts to 

 prevent the spread of infection in the incubator have been only partly suc- 

 cessful. The amount of dissemination in the incubator may be reduced to 

 some extent by fumigation and special handling, but it can never be com- 

 ])letely prevented by these methods because they fail to kill the organism in 

 the live chick. Fumigation may be of some benefit in destroying the organ- 

 ism, but it may also be injurious to the chicks. The time, effort, and expense 

 associated with these methods should be directed toward effective measures 

 of eradication and prevention. Flocks frequently become infected through 

 such practices as custom hatching and having eggs hatched in incubators 



