576 bytes added
, 19:39, 18 October 2008
{{unfinished}}
{{toplink
|linkpage =Viruses
|linktext =VIRUSES
|sublink1=Retroviridae
|subtext1=RETROVIRIDAE
|pagetype =Bugs
}}
<br>
====Antigenicity====
3 subgroups of note:
*A and B are found in 10% of layers, causing occasional B cell leukosis
*J has been found in up to 40% of broilers causing up to 10% of deaths by myeloid tumors
====Epidemiology====
*All three subgroups are transferred vertically and horizontally
====Control====
*Selective breeding has now controlled the virus:
**Hens whose eggs testing positive for antigen in albumin are removed from the flock