30 MASS. EXPERIMENT STATION BULLETIN 337 



SUMMARY AND CONCLUSIONS 



The Leukotic Diseases 



1. Erythroleukosis and myeloleukosis are filterable virus diseases, and the 

 filterable agents are contained in the blood stream independent of the cellular 

 elements. Chickens under a year old are more susceptible than older birds. 

 Predisposing factors appear to be mites, warm weather, and overcrowding. 



2. An outbreak of monoleukosis is reported as distinct from erythroleuko- 

 sis and myeloleukosis. 



3. Lympholeukosis is due to a histogenous cell identified by the vesicular 

 arrangement of the chromatin of the nucleus. It is usually found infiltrating 

 the tissues of the liver and spleen, and free in the portal blood of affected 

 chickens. The living lympholeukotic cell is resistant to vital stains such as 

 trypan blue, but the dead cell readily absorbs trypan blue. Lympholeukosis 

 was transmitted from diseased to healthy chickens by inoculating portal blood 

 containing large numbers of the living cells directly into the blood stream or 

 the abdominal cavity. 



Neurolymphomatosis 



4. Neurolymphomatosis or avian paralysis is due to a histogenous cell 

 indistinguishable from that occurring in lympholeukosis, except that it has a 

 special predilection for the nervous system, and under conditions not very well 

 understood, it may invade other adjacent tissues. Chickens inoculated in the 

 nervous system with living cells developed neurolymphomas distally to the 

 point of inoculation in the nerves of the limbs. 



5. The evidence indicates that the neurolymphomatous cell was transmitted 

 from the hen and possibly from the rooster to the chicken through the egg. The 

 exact method by which the egg is affected was not determined, although 

 neurolymphomatous cells were found infiltrating ovules in affected hens and 

 cells indistinguishable from them were found in the semen of affected roosters 

 and the follicular fluid of diseased hens. The ovaries and testes of active 

 transmitters were found at necropsy to be infiltrated with neurolymphomatous 

 cells, and no hen or rooster was incriminated in this study as a transmitter that 

 did not show such infiltration of the reproductive organs at some time. 



6. Symptoms appeared in affected chickens in from 2 weeks to 10 months. 

 The average period for the 66 birds in this study was 188.85 days or about 

 6 months. 



7. During the course of these observations and experiments, evidence was 

 secured which indicates that hereditary factors involving resistant and suscept- 

 ible birds were found in certain forms of neurolymphomatosis, particularly in 

 the infiltration of the ovules of the ovary and the nerve of the eye. 



8. In conclusion it should be pointed out that the experiments reported in 

 this bulletin were directed toward a study of those forms of neurolymphomatosis 

 which affect the ovary and testes, and of the methods whereby the disease is 

 transmitted through the egg. Transmission through the egg, however, may not 

 be the only way or even the most important way in which the disease is spread. 



