Fig. 2

Leucocytozoon spp. tissue stages in kidney sections of accipitriform birds, detected by HE-staining and CISH (inserts). Meronts were frequently observed in epithelial cells of renal tubules and labelled by the L. toddi-specific probe (inserts, CISH). a–d Meronts (black arrows) detected in the kidneys of several Buteo buteo co-infected with L. buteonis lBUBT2 and L. aff. toddi lBUTBUT03. The meronts were of irregular shape and contained numerous basophilic merozoites. Several smaller meronts were located in renal epithelial cells (d). e–f Meronts detected in renal tubules of a Buteo buteo infected with L. buteonis lBUBT2. Mature meronts packed with merozoites often occupied the entire intracellular space of infected epithelial cells, causing protrusion into the tubular lumen and lateral displacement of the host cell nucleus (e, white arrow). g–i Meronts detected in renal tubules of a Buteo buteo infected with L. aff. toddi lBUTBUT12. Meronts shown in g and h contained nuclear material but developing merozoites were not discernible, indicating early stage of parasite development. Other meronts were more mature and contained developing merozoites (i). j A mature meront detected in a kidney tubule of a Buteo buteo co-infected with L. buteonis lBUBT2 and L. aff. toddi lBUTBUT07. k–l Developing meronts detected in a Circus aeruginosus co-infected with L. aff. toddi lCIAE03 and P. circumflexum pTURDUS1. Black arrow = meront, white arrowhead = host cell nucleus. All scale bars = 50 µm