Effect of Infectious Bursal Disease Virus Infection on the Phagocytosis of Staphylococcus aureus by Mononuclear Phagocytic Cells of Susceptible and Resistant Strains of Chickens

Studies were conducted to determine why chickens infected with infectious bursal disease (IBD) are more susceptible to Staphylococcus aureus. We evaluated the effect of IBD virus on functions of the peripheral mononuclear phagocytes and looked for humoral abnormalities in the serum. An in vitro opsonophagocytic assay using (H3) thymidine-labeled opsonized Staphylococcus aureus was used to measure phagocytosis. Infection of IBD-sensitive (SCWL 420) chickens with IBD virus did not cause any cellular defects, as shown by phagocytic inability, or any humoral abnormalities, as shown by the lack of opsonics. However, IBD virus did cause some humoral defects 2 weeks postinfection in resistant (Hardy Red) chickens. Therefore, the basic mechanisms governing increased susceptibility of IBD-infected chickens to S. aureus is still unknown.