4 MASS. EXPERIMENT STATION BULLETIN 337 



The experimental data reported in Table 2 indicate that the causative agent 

 in myeloleukosis is in the blood of affected chickens. 



Also, this experiment shows a possible age resistance to the disease, since the 

 older or 24-weeks-oId chickens were more resistant to myeloleukosis than either 

 the eight- or two-weeks-old birds. None of the 60 chickens on this experiment 

 showed any symptoms or lesions of neurolymphomatosis, which demonstrates 

 that the two diseases are etiologically separate. 



In order to test the filterability of myeloleukosis for comparison with neuro- 

 lymphomatosis and other forms of leukemia included in this study, the same 

 procedure was followed as was used to determine a similar property of ery- 

 throleukosis. The results appear in Table 2. 



Table 2. — Results of Inoculating Chickens with Myeloleukotic 



Blood and Plasma 



Myeloleukotic 

 Number of Age Unaffected 



Chickens (Weeks) Total Died Recovered 



Inoculated with Whole Myeloleukotic Blood 



20 2 7 13 11 2 



20 8 10 10 7 3 



20 24 12 8 3 5 



60 29 31 21 10 



Inoculated with Myeloleukotic Plasma 



20 2 10 10 7 3 



20 8 14 6 4 2 



20 24 17 3 3 



60 41 19 11 8 



The results of the experiments recorded in Table 2 indicate that myeloleuko- 

 sis was due to an ultrafiltrate, found in the blood stream separate from the 

 corpuscles and platelets during the course of the disease. 



The results of these experiments on erythroleukosis and myeloleukosis, while 

 not extensive, are in agreement with similar findings reported by Furth (1931), 

 and indicate that both diseases are due to a filterable agent in the blood stream. 

 While mixed cases of these two types of leukosis have been found in Massa- 

 chusetts flocks, the diseases reported in this bulletin were entirely separate. 

 According to the records of the Diagnostic Service, myeloleukosis appears to 

 be more common in Massachusetts than erythroleukosis, and largely for this 

 reason an attempt was made to discover if red mites (Dermanyssus gallinae) 

 were in any way responsible for the transmission of this disease from sick to 

 healthy birds. It was thought that since the virus existed in the blood of 

 affected birds this insect might be incriminated as a vector. 



