**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** TURKEY REOVIRUSES CAUSING LAMENESS IN MARKET AGE TURKEYS HAVE BEEN RECOGNIZED IN THE US SINCE 2011. SIGNIFICANT ECONOMIC LOSSES ARE INCURRED DUE TO POOR WEIGHT GAIN, MORTALITY, AND CONDEMNATIONS AT THE PROCESSING PLANTS. CURRENTLY, THERE IS NO EFFECTIVE MEASURES TO CONTROL AND PREVENT REOVIRAL ARTHRITIS IN TURKEYS. TO LAY THE GROUNDWORK FOR DEVELOPMENT OF EFFECTIVE CONTROL MEASURE, EMERGING TURKEY REOVIRAL ARTHRITIS NEEDS TO BE COMPREHENSIVELY DEFINED. IN THIS STUDY, WE WILL STUDY TURKEY REOVIRAL ARTHRITIS IN CONTEXT OF AGE-BASED HOST RESPONSES. WE WILL EVALUATE THE EFFECT OF AGE ON TISSUE TROPISM OF THE VIRUS, LEVEL OF VIRUS REPLICATION, AND THE ONSET AND SEVERITY OF THE DISEASE. WE WILL ALSO INVESTIGATE HOW NATURAL INFECTION-INDUCED AND PASSIVELY ACQUIRED MATERNAL IMMUNE RESPONSES AFFECT THE ONSET AND DEVELOPMENT OF REOVIRAL ARTHRITIS. IN ADDITION, WE WILL DETERMINE HOW MICROBIOME MODULATION BY PROBIOTIC AFFECTS DISEASE OUTBREAK AND SEVERITY. OUR STUDY WILL NOT ONLY ENHANCE OUR UNDERSTANDING OF THE MECHANISM OF TURKEY ARTHRITIS BUT ALSO HAVE THE POTENTIAL OF UNRAVELING A NOVEL METHOD OF CONTROLLING REOVIRAL DISEASE IN TURKEYS. ADDITIONALLY, INFORMATION OBTAINED FROM THIS STUDY CAN BE APPLIED TO DEVELOP CONTROL AND PREVENTION MEASURES AGAINST OTHER ECONOMICALLY IMPORTANT POULTRY ENTERIC VIRAL INFECTIONS.