[Influence of environmental factors on the infection rates of fishes and shellfishes by trematodes of the Opisthorchidae family in the Krotovaya Lyaga Lake].

The relationship of the annual trends in the infection of crucians (Carassius carassius) (L.) with Opisthorchis felineus metacercariae, in that of verkhovkas (Leucasplius delineatus) (Hackel), and in that of lake minnows (Phoxinus percnurus) (L.) with O. felineus and Metorchis billis to the environmental factors under natural fluctuations of the level of water and under the man-made effects on the water regime of the reservoir was studied. When the level of water naturally changes, the infection of crucians with Metorchis was found to be affected by their size, water temperature, and environmental pH values, and the human Opisthorchis affliction depends on the severity of infection of commercial-sized crucians by metacercariae. The infestation of the verkhovka was determined by the temperature of water and that of the lake minnow was by its size and the increased areas of the lake with the depths salubrious to its existence. With man-made effects (dewatering for watering agricultural lands) on the water regime of the reservoir, the infestation of the lake minnow depended on its size in the shallow water and on the level of water. Environmental factors, such as pH values, the area of shallow waters, and the size of mollusks, positively affected the higher extensiveness of infestation of mollusks with the parthenitae of opisthorchid flukes.