Synergy of subgroup J avian leukosis virus and Eimeria tenella to increase pathogenesis in specific-pathogen-free chickens

To investigate the effects of co-infections of subgroup J avian leukosis virus (ALV-J) and Eimeria tenella on the pathogenesis in specific-pathogen-free (SPF) white leghorn chickens, groups of chickens were infected with ALV-J strain NX0101 at one day of age or with E. tenella at 14 days of age or both. The control group was left uninfected and was mock-inoculated with phosphate buffer saline (PBS). Mortality rates, body weights, cecal lesions, and viremia of infected chickens in each group were evaluated. Immune status was evaluated by measuring several parameters: immune organ weight/body weight index, specific humoral responses to inactivated NDV vaccine and to inoculated E. tenella, proportions of blood CD3 + CD4+ and CD3 + CD8α+ lymphocytes and transcriptional levels of cytokines in blood and cecal tonsils. The results show that co-infections of ALV-J and E. tenella induced a higher mortality rate and a lower body weight in SPF chickens compared to single-pathogen infection. In co-infected chickens, ALV-J accelerated the disease symptoms induced by E. tenella, and the E. tenella extended the ALV-J viremia. Thymus atrophy, decrease in the humoral response levels to pathogens and the NDV vaccine, modifications in the blood lymphocyte sub-populations and transcriptional cytokine disorders were found in co-infected chickens compared to chickens infected with one pathogen alone and to controls. We underline a synergy between ALV-J and E. tenella that results in increasing pathogenesis in SPF chickens.