Immunohistochemial tissue sections from rainbow trout fry concurrently infected with
and infectious pancreatic necrosis virus (IPNV). A Immunohistochemia image for exocrine pancreas shows blue reaction for F. psychrophilum and red-brown for IPN virus. Note single bacteria (arrow), without counterstaining, X530. B Immunofluorescent section from head kidney shows red fluorescence for IPN virus in the cytoplasm of interstitial cells and the presence of bacteria either alone or as a group at the lower right with green fluorescence, X660. C Higher power magnification for immunofluorescent mid kidney shows IPN virus in the cytoplasm of the interstitial cell. Endothelial cells lining the tubulus show positive staining for both IPN virus and F. psychrophilum possibly in the same cell (arrow), X833.