Fig. 5

Comparative histopathology of WD on rainbow trout during single and co-infection with PKD. a Epidermis showing numerous intracellular aggregates of dark stained sporoplasms between the epithelial cells 30 min post-exposure to M. cerebralis (arrow). b Cranium of single Mc infected group, 60 dpe shows presence of cartilaginous necrotic foci containing numerous developmental stages of parasite (inset, arrowhead). c Cranium of Mc-then Tb co-infected group, 60 dpe to Mc (30 dpe to Tb) showing severe cartilage destruction involves most of the cartilage and infiltration of inflammatory tissues (star). d Single Mc infected group at 90 dpe showing presence of numerous mature myxospores in the area of cartilage necrosis (inset, arrow) with infiltration of macrophages and lymphocytes. e Mc-then Tb co-infected group, 90 dpe to Mc (60 dpe to Tb) showing severe destruction of cranial cartilage with displacement (star). f Affected cranial cartilage of single Mc infected group at 120 dpe showing presence of multinucleated giant cells in the site of granulomatous inflammation (arrow). g Cranium of Tb-then Mc co-infected group, 90 dpe to Tb (60 dpe to Mc) showing presence of small discrete foci of degenerated cartilage (arrow) and containing few generative stages of M. cerebralis with few leukocytes (inset, arrow). h Cranium of Tb-then Mc co-infected group, 120 dpe to Tb (90 dpe to Mc) showing presence of mild cartilagneous degeneration and necrosis with few chronic inflammatory cells surrounding the affected cartilage (arrow) and presence of few mature myxospores (inset, arrow). H&E staining. Scale-bars: a, 20 μm; b, 100 μm (inset 50 μm); c, 200 μm; d, 200 μm (inset 20 μm); e, 200 μm; f, 100 μm (inset 20 μm); g, 200 μm (inset 50 μm); h, 200 μm (inset 20 μm)