TREMATODA AND CESTODA SPECIES IN CYPRINID FISH FROM SMALL LAKES OF THE KOSTANAY REGION

Abstract

This study presents data on the epizootiological monitoring of parasitic diseases in fish from Kostanay region. It confirms the presence of previously identified permanent natural foci of opisthorchiasis in the southern districts, specifically in the Uly-Zhilanchik and Torgay rivers. Additionally, the research conducted in Zhangeldy and Amangeldy districts revealed the existence of biohelminths with both epizootiological and epidemiological significance. This study aimed to investigate the presence of parasites dangerous to humans and carnivores in cyprinid fish species. Specifically, it focused on identifying the second intermediate hosts for opisthorchiasis, metorchiasis, and ligulosis: ide (Leuciscus idus) and bream (Abramis brama). From 2021 to 2023 seven reservoirs of the Kostanay region were the monitoring objects of the parasitological situation: Verkhnetobolskoe reservoir, rivers: Torgay, Uly-Zhilanchik, Zhaldama, Tobol, Zhelkuar, Akkol Lake, where shellfish bitiniids, waterfowl and crustaceans live in large numbers, as the first intermediate host of pathogens Opisthorchis felineus (Metorchis bilis), Ligula imestinalis. Examination of eight ide (Leuciscus idus) specimens caught in the Uly Zhilanchik River revealed the presence of metacercariae of two parasitic trematodes: O.felineus and M.bilis, while the prevalence was 18.5% and 8.3%, and the infestation intensity was 1-3 and 2, respectively. In the Amangeldy region, metacercariae O. Felineus and plerocercoids Ligula imestinalis were found in two fish species: one individual of the ide species and two individuals of the bream species caught from the Torgai River. At the same time, the prevalence was 6.6% and 16.6%, and the infestation intensity was 2 and 1, respectively. Parasitic diseases of fish were not detected in the waters of Denisovsky and Zhitikarinsky districts. Based on Polymerase Chain Reaction (PCR) analyses conducted using specific primers at the National Center of Biotechnology LLP laboratory in Astana, Kazakhstan, two distinct types of opisthorchid parasites were identified in two ide (Leuciscus idus) specimens collected from Kostanay region. The species were confirmed to be Opisthorchis felineus and Methorchis bilis (PCR protocol dated April 24, 2023).