Myotropic avian leukosis virus subgroup J infection in a chicken.

The study describes a highly productive myotropic avian leukosis virus infection (ALV) in a 3-month-old female chicken. At necropsy, ascites, hepatic fibrosis and cardiomegaly were seen. Histologically, the most striking lesion was the presence of cytoplasmic basophilic inclusions in myocardial fibers. Immunostaining for ALV group specific antigen p27 revealed a diffuse presence of virus antigen in cardiac myofibers, in smooth muscle fibers of most of the organs, and in rare, pancreatic and ovarian theca cells. Ultrastructurally, myocardial inclusions consisted of clusters of 50-60 nm round particles with interspersed ribosome-like granules. Numerous C-type particles were found in intercellular spaces of ALV p27 positive tissues. PCR analyses revealed the presence of both ALV-E and ALV-J related sequences. In chicken genome, ALV-E is usually present as endogenous provirus therefore, the pathological findings observed in this case are considered to be related with the ALV-J infection. The results of this report further confirm that ALV-J may be responsible for highly productive myotropic infections.