Distribution of Trematode Metacercaria in Cyprinid Fish in Natural Reservoirs of the Lipetsk Region

Applied parasitology considers cyprinid fish as a source of infection of humans and domestic animals with zoonotic trematodes. A preliminary assessment of the species diversity of trematode metacercariae was carried out on one reservoir (Usman River) in the Lipetsk Region in 2021-2022. In 2023, the geography of collections was expanded; research was carried out on five rivers in the southern part of the Lipetsk Region. The materials were collected on rivers Voronezh, Matyra, Sosna, Snova, and Usman. We examined 197 cyprinid fish of 8 species: roach (57 specimens), bleak (22 specimens), rudd (42 specimens), silver bream (43 specimens), bream (3 specimens), dace (6 specimens), Prussian carp (17 specimens) and gudgeon (7 specimens). Eight trematode metacercariae species were recorded, the total prevalence for 8 cyprinid species was 87.3%. The highest prevalence rates were observed for metacercariae Pseudamphistomum truncatum, Paracoenogonimus ovatus and Posthodiplostomum cuticula; half as high for Opisthorchis felineus, Metorchis bilis and Metorchis xanthosomus; and minimal for Rhipidocotyle campanula and Apophallus muehlingi. Distribution irregularities were detected for trematode metacercariae in individual reservoirs. The most common was P. ovatus recorded in all cyprinid species.