Mixed infections of Marek's disease and reticuloendotheliosis viruses in layer flocks in Argentina.

The presence of reticuloendotheliosis virus (REV) was examined in flocks affected with Marek's disease (MD). Sera were positive to REV antibodies by agar gel precipitation. However, these findings were not conclusive since fowlpox vaccines can have REV fragments or the whole genome inserted. Frozen sections from tumors were positive for MD virus (MDV) but negative for REV. Chicken embryo fibroblast (CEF) and chicken kidney cell (CKC) culture inoculated with buffy coat cells or blood from the affected birds were examined. Positive cells were shown for REV and MDV by fluorescent antibodies tests in CEF and CKC, respectively, indicating the presence of REV in Argentinean layer flocks. This is the first report of REV in Argentina and also in South America.