Pathogenesis of reticuloendotheliosis virus infection in ducks

A new isolate of reticuloendotheliosis virus (REV) from ducks, RU-1, was used to experimentally infect white pekin ducks. Embryonal or neonatal infection usually resulted in persistent viremias, no REV antibody development, and inability to mount antibody responses against bovine serum albumin (BSA) or sheep red blood cells (SRBC). In contrast, infection at 21 days of age resulted in transient viremias, which terminated coincident with REV antibody development. These ducks remained persistently infected, however, based on virus isolations from peripheral blood lymphocytes. Ducks infected at that age were immunologically competent against BSA and SRBC unless they had been embryonally bursectomized, in which case they behaved virologically and immunologically like those infected at an early age. Bursectomy by itself did not prevent responses against the antigens. Total mortality during 4- or 6-month experimental periods ranged from 80 to 100% in REV-infected groups, regardless of age at infection, route of exposure, or whether the ducks were intact or bursectomized. Most deaths were from non-neoplastic conditions (stunting, bacterial infections), but 17 of 69 (25%) infected ducks developed a variety of neoplasms, including lymphosarcomas, histiocytic sarcomas, and spindle-cell sarcomas.