Effect of experimental Diphyllobothrium dendriticum infection on the blood leucocyte pattern of brown trout at two temperature levels

Leucocyte composition in the peripheral blood of brown trout Salmo trutta m. lacustris (L.) aged 1+ was studied in relation to Diphyllobothrium dendriticum (Cestoda) infection at two temperature levels, heated about 15 °C and non-heated which decreased from 11 °C to 7 °C. Blood samples were taken from control and infected fish 12 weeks post infection. The D. dendriticum infection (1–6 per fish) had a significant increasing impact on lymphocyte and neutrophil counts at both temperature levels while thrombocytes were more numerous in control fish, particularly in non-heated water. The total leucocyte counts were not influenced by the D. dendriticum infection. The present water temperatures created differences only in thrombocyte and total leucocyte counts, which were increased in non-heated aquaria.