6 CONTROL SERIES No. 58 



birds are "carriers" of tlie disease. One may find such birds which are not 

 infected, but their small size and weak vitalitj' are the results of infection 

 durint;^ a period earlier in life. Furthermore, "carriers" are not limited to 

 under-developed birds, since frequently one may find that the best developed 

 birds in the flock are infected. 



Mortniiti/ amoiuj nrlults. — Occasionally one may observe heavy losses associ- 

 ated with acute outbreaks in adults. Frequently a single infected bird may 

 succumb to the disease, especially if its resistance has been lowered by other 

 factors. In such instances, it is not infrequent that iS. pullorum may be re- 

 covered froiu organs such as the heart, the liver, the spleen, the ovary, and 

 other lesions. 



Lowered egg production. — Repeated investigations have shown that egg 

 production in general is lower among infected birds than among non-infected 

 birds of the same breeding. In some infected birds egg production is not 

 lowered, since the particular localization of the infection and the extent to 

 which the ova are diseased appear to be the influencing factors. Culling the 

 low producing birds should not be regarded as a method of eliminating 

 pullorum disease from a flock, because the high producing, infected individu- 

 al and the infected male would remain in the flock. 



Reduced salability of froducts.- — Poultrymen who have once experienced 

 losses from pullorum disease through negligence of proper precautions are 

 not likely to risk repeating the experience. The losses involved are often 

 costly and may even lead to a failure in business. The majority of those who 

 are correctly informed about losses associated with this disease will purchase 

 eggs or stock from a non-infected flock and will exercise every jjrecaution 

 against exposing their eggs or stock to sources of infection. Eggs or stock 

 from pullorum disease-free flocks have increased salability and command 

 higher prices. 



Spread of Infection 



Among adults. — In adults the disease may spread through contact of in- 

 fected with non-infected birds, as has been demonstrated frequently. Just 

 how the infection is eliminated from the diseased bird and transmitted to the 

 uninfected is not clearly and completely comprehended. It is known that the 

 infection may localize in the heart sac and heart nmscle, liver, gall bladder, 

 spleen, kidneys, free and attached cysts, testes, ovary, and oviduct. If the 

 infection remains localized in the heart, spleen, or fixed body cavity cysts, the 

 opportunity for elimination of the organism appears to be negligible. If lo- 

 calized in the liver, gall bladder and kidneys, or testes, the lesion might be 

 of such a nature as to permit elimination of the organism through the intest- 

 inal tract, and tubes leading from the kidneys or testes to the cloaca. The 

 organism has been isolated from the intestinal tract and also from the nasal 

 sinuses of naturally infected birds. Isolation from the latter organ has been 

 reported only once. 



Adults may be artificially infected by injecting the organism into the blood 

 stream, body cavity, under the skin, or into the oviduct; by feeding; and by 

 dropping into the eye. 



The r61e that the male bird plays in disseminating the infection has not 

 been definitely determined. Males may become naturally infected. Based 

 upon agglutination tests, the percentage of infected males as compared with 

 females is less. 



