Turkey origin reovirus-induced immune dysfunction in specific-pathogen free and commercial turkey poults

Authors: Day, James; Spackman, Erica; Pantin Jackwood, Mary

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2008
Publication Date: 9/1/2008
Citation: Day, J.M., Spackman, E., Pantin Jackwood, M.J. 2008. Turkey-origin reovirus induced immune dysfunction in specific-pathogen free and commercial turkey poults. Avian Diseases. 52:387-391.

Interpretive Summary: Enteric disease consistently results in economic loss for the poultry industry due to poor weight gain and the inability of young chickens and turkeys to utilize their feed properly. Recognized enteric disease syndromes such as Poult Enteritis Complex (PEC), Poult Enteritis Mortality Syndrome (PEMS), and Runting-Stunting Syndrome (RSS) continuously occur in poultry producing areas of the United States. The specific infectious agents (viruses or bacteria) that cause these syndromes is presently unknown, and disease signs such as diarrhea and poor weight gain are difficult to reproduce in controlled laboratory experiments. It is likely that PEC, PEMS, and RSS are each caused by the interaction of multiple viruses and perhaps bacteria acting together to cause disease. Previous work in our laboratory revealed that an isolated avian reovirus—a small virus often found in the gut and/or droppings of poultry with enteric disease—can damage an avian organ called the bursa that is important in the immune response in infected birds. This led us to the hypothesis that an infection with a reovirus may negatively impact the ability of a turkey or chicken to fight off the ongoing reovirus infection or a later infection with another virus. This study used two assays to measure the strength of the immune response in young turkeys infected with an isolated reovirus. We also verified our earlier observations that infection with a reovirus can cause moderate to severe damage to the bursa. Our findings suggest that an infection with a reovirus can significantly affect the ability of a young turkey to mount an immune response (i.e., produce antibodies to a subsequent viral infection). This effect on the immune system was noted in turkeys infected with reovirus at a very young age (3 days old) and not in turkeys infected with reovirus at three weeks of age.

Technical Abstract: Recently, pathogenesis studies using genetically distinct turkey-origin reoviruses (TRVs) revealed that poults infected with certain TRV isolates had moderate to severe bursal atrophy, suggesting virus-induced immune dysfunction. In order to characterize the effect of TRV infection on the turkey immune system, classical assays were undertaken to quantify the humoral and cell-mediated immune responses in small Beltsville and Broad-breasted white poults infected the TRV isolate NC/SEP-R44/03. A marked effect on the cutaneous basophil hypersensitivity response and on the antibody response to Newcastle disease virus (NDV) exposure was noted in commercial and SPF poults inoculated with NC/SEP-R44/03 at three days of age. Commercial poults inoculated at three days of age had moderate to severe bursal atrophy similar to that noted previously in SPF poults. This immune dysfunction and bursal atrophy was not noted in commercial poults inoculated at three weeks of age.