Evaluating how infectious bursal disease virus influences influenza A virus transmission in chickens

Infectious bursal disease virus (IBDV) is a major cause of immunosuppression in chickens that has been shown to affect influenza A virus (IAV) pathogenicity and shedding patterns. In this study, we compared the shedding of a low passage duck origin IAV in two groups of specific pathogen-free chickens: one group that was IBDV-inoculated and one sham-inoculated group. At three weeks age, the birds were divided and given one of three doses (102, 103 or 105 TCID50/bird) of A/mallard/OH/421/1987 (H7N8) low pathogenicity avian influenza virus. Although the bursae of the IBDV-infected chicks had significantly higher histological damage scores, the overall harm to lymphoid follicles was minimal. What we observed was that this low IBDV exposure increased resistance to IAV challenge. The ID50 for the IBDV:IAV groups was 6x104 /ml while it was 1.7x104 /ml for the IAV only groups. Virus shedding was similarly affected with the IBDV:IAV group shedding an average of 2.8 days (range 1-6 days) and the IAV only group shedding for an average of 7.9 days (range 1-10 days). All of the uninoculated contacts co-housed with each of the treatment groups at the 105 dose level as well as all those placed with the 102 IAV only treatment group were infected. These findings demonstrate that the impacts of immunosuppressive agents may vary in their impacts on IAV challenge based on the severity of immunosuppression and may, at low doses, confer some level of protection.

Peter Bonney, University of Minnesota Marie Culhane, University of Minnesota Cristian Flores, University of Minnesota Jeannette Munoz, University of Minnesota Kristelle Mendoza, University of Minnesota

Transmission pathways, pathobiology, immune responses