THE IMPACT OF A PARASITE LOAD ON FISH ORGANISM RESISTANCE IN EXTREME ENVIRONMENT

This paper analyzed the impact of parasite cenosis in extreme environment on the resistance of the steelhead trout (Oncorhynchus mykiss) organism. We considered a parasite cenosis complex consisting of Trichodina sp. and Aeromonas hydrophila which causes clinical manifestations in salmonids, to demonstrate the possibility of using blood parameters to assess the resistance of the fish organism. The studies revealed that the parasite complex infection leads to a decrease in erythrocytes by 34% as compared to the control group. The hemoglobin value was lower by 30.3%. The serum protein decreased by 40.2%. Lysozyme activity was found to be increased by 45.9%. It was found that phagocytic activity of leukocytes was 8.48% higher in group 1 than in the control animals. It is noted that this value was 15.9% lower under external hypoxia conditions than in the control group. Therefore, when assessing the Oncorhynchus mykiss resistance, it is necessary to consider potential extreme exposure to environmental factors and a possible parasite load which can increase a degree of a damaging factor and plays an important role in the formation of adaptive processes.