Synergetic effects of subgroup J avian leukosis virus and reticuloendotheliosis virus co-infection on growth retardation and immunosuppression in SPF chickens

•One-day-old SPF chicks were infected with ALV-J and REV alone or both.•Co-infection of ALV-J and REV induced stronger growth retardation and higher mortality than single infection (P < 0.05).•Co-infection caused more severe immunosuppression than single infection (P < 0.05).

To further understand the effect of co-infection of subgroup J avian leukosis virus (ALV-J) and reticuloendotheliosis virus (REV) in specific-pathogen-free (SPF) white leghorn chickens, the experiment was made to study the pathogenicity, the weight of body and immune organs, response to newcastle disease virus (NDV) and avian influenza virus subtype H9 (AIV-H9) vaccination. Chickens were randomly divided into four groups, which includes injection groups (REV, ALV-J, REV plus ALV-J), and negative control group. The pathogenesis experiments indicated that chickens co-infected with REV and ALV-J had significantly higher mortality rate than those of the chickens infected with REV or ALV-J alone (P < 0.05). Chickens inoculated with REV and ALV-J had significantly lower weights than chickens in all other groups (P < 0.05). There were no significant differences between the two single infection groups and co-infection group (P > 0.05) on bursa and thymus over body wt ratios, however, chickens co-infected with REV and ALV-J had significantly lower titers than REV-infected chickens and ALV-J-infected chickens on HI antibody titers to ND and AIV-H9 after vaccination (P < 0.05). These findings suggested that the co-infection of REV and ALV-J caused more serious growth retardation and immunosuppression in SPF chickens.