Interaction of Marek’s Disease Virus and Reticuloendotheliosis Virus in Co-infected Broilers

To understand the interaction between Marek’s disease viruses (MDV) and Reticuloendothe -liosis viruses (REV) in co-infected chickens, their mutual influences on vriremia levels and specific antibody titiers were studied in REV maternal antibody positive (REV-ab+) or negative (REV-ab-) commercial broilers vaccinated with or without MDV vaccine CVI988. The results indicated that REV viremia did not influence the MDV viremia level and antibody titers after inoculation with virulent MDV in unvaccinated chickens. In chickens vaccinated with CVI988, however, REV viremia could significantly inhibit antibody titers (p0.01) and resistance to MDV, and compromised protective effect of CVI988 vaccine from MDV viremia in vaccinated birds. In another hand, MDV infection could decrease the resistance to REV infection in REV-ab+ chickens. REV inoculation caused no REV viremia in REV-ab+ chickens without MDV viremia but caused high titers of REV viremia in REV-ab+ chickens with MDV viremia. MDV viremia also decreased antibody responses to REV inoculation in REV-ab+ chickens. Analysis of the data suggested that co-infection of MDV and REV could influence each other’s pathogenicity mainly through their inbibitory effects on chicken’s immune functions.