Expansion of the area of the trematodes <i>Paracoenogonimus ovatus</i> (Katsurada, 1914) in Western Siberia

The distribution of trematodes Paracoenogonimus ovatus and its first intermediate hosts, viviparous Viviparus viviparus and V. contectus in the Ob–Irtysh basin were analyzed. Until the 1990s the spreading of P. ovatus in this region was associated with habitats of V. contectus, which is considered a native species in Western Siberia. Since the mid-1990s European species V. viviparus began to spread in the Ob basin. Before this, only one source of infection with P. ovatus was known associated with finding V. viviparus in the Lower Irtysh. This paper describes another such outbreak in the Tura River near the city of Tyumen. In fish from the Tura River, a generally high extent and intensity of invasion were noted. Further expansion of the range is predicted P. ovatus associated with expansion V. viviparus.