Pathophysiology of Ichthyophthirius multifiliis Infection in Rainbow Trout (Oncorhynchus mykiss) and Chub (Leuciscus cephalus)

SummaryThe present study investigated the effect of experimental infection with Ichthyophthirius multifiliis on physiological, immunological and metabolic parameters in rainbow trout (Oncorhynchus mykiss) and chub (Leuciscus cephalus). Both species developed an immune response against I. multifiliis that was detected in the peripheral blood (i.e. increase in immunoglobulin concentrations in rainbow trout, increase in lymphocyte and thrombocyte concentrations in chub), but not in the skin mucus. Anaemia was observed in both species of fish. In rainbow trout there was also depletion of liver glycogen, disturbance in osmoregulation (decrease in serum osmolality and Na+ and Cl− concentrations) and possibly also impaired wound healing capacity (i.e. decrease in skin mucus alkaline phosphatase and β-glucuronidase activity). Therefore, rainbow trout develop more severe changes following this infection compared with chub.