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The most mass commercial carp fish from two fish sites of the Lower Ob and one from the river Middle Ob were investigated in 2016. The maximum infestation of opisthorchis were observed of the Ide with most of the indicators of extensiveness and intensity of infestation, then descending roach and bream. The contamination of an the ide Opisthorchis felineus metatcercaria on the river Middle Ob reached 100 %, in the Northern direction it decreases to 90%. Studies of in Lower Ob the ide and roach, frozen for 7 hours or more at a temperature of minus 40°C showed complete death of opisthorchid larvae
Осипов et al. (Fri,) studied this question.