NEUROLYMPHOMATOSIS 5 



Experiments with Red Mites 



Four chickens having advanced myeloleukosis were placed in a flock of 19 

 healthy pullets and one healthy rooster which had never been exposed to leu- 

 kosis in any form. Red mites were abundant in this house. All of the chickens 

 on this experiment were three months old and the disease was allowed to run 

 a natural course for one year. The experiment was started May 24, 1934, and 

 was closed on May 24, 1935. During this period the birds were blood-counted 

 weekly in order to detect the earliest symptoms of myeloleukosis. The results 

 are recorded in Table 3. 



Table 3. — Chickens Exposed to Natural Infection With 

 Myeloleukosis in a House Infested with Red Mites 



Pullets MG-52468, MG-52469, MG-52473 and MG-52481, already affected 

 with the disease when placed in the pen, died on the 4th, 7th, 12th and 13th 

 days of the experiment. 



Cockerel MG-52482 contracted the disease first. He had been in the house 

 only four days and died on the 14th day of the experiment. He was replaced 

 by a half-brother, MG-52502, which lived through the remainder of the ex- 

 periment in good health. Pullets MG-52486, MG-52488, MG-52485 and MG- 

 52501 contracted the disease before freezing occurred in the hen house, and 

 MG-52497 did not show any indications of myeloleukosis until after some 

 freezing weather had taken place and the red mites were not active. No infec- 

 tion took place in this flock after December 27, 1934, although the virus was 

 known to be present in at least one affected bird, MG-52499, up to January 

 9, 1935. In other words, five of the pullets and one of the cockerels contracted 

 myeloleukosis during the first six months of the experiment, and only one 

 MG-52499, contracted the disease during the last part of the experiment. 

 Thirteen of the pullets remained unaffected during the entire period. 



