Prevalence of the nematodes Eustrongylides exisus Jägerskiöld, 1909, – larvae (Nematoda: Dioctophymatidae) infection in the Rutilis rutilis, linnaeus 1758 and the seasonal dynamics of the infection in the waters of the Dnipro-Buh estuari in southern Ukrai
In this study, we determined the prevalence and seasonal dynamic of the infection of the Rutilis rutilis, Lіnnaeus 1758 with the nematode Eustrongylides excisus. The fish was caught in the waters of the Dnipro-Buh estuary in seven sample collection sites between 2016 and 2019. They all underwent ichthyopathological examination. Parasites, found during examination, undergone microscopy to determine their taxonomy. Overall 595 specimens were obtained. The mean prevalence of infection over entire study period (2016–2019) was 17.4 %. Ichthyopathological examination of the roach caught in the waters of the Dnipro-Buh estuary revealed the infection with larvae E. excises nematode. The parasitic larvae were found in the muscles of the ventral abdominal wall of the roach. There was more than two-fold difference in the prevalence of infection between sample collection sites – from 12 % in site 5 near Sofiivka to 28 % in site 3 near the village Oleksandrivka over the study period in 2016–2019. The total prevalence of infection in roaches in the Dnipro-Buh estuary was 17.4 %. Seasonal changes were not statistically significant and ranged from 12.8 % in summer to 20.1 % in spring. Annual changes suggested a possible upward trend, but more observations are needed to confirm it. Аnnual changes were not statistically significant. The prevalence of infection changed throughout the year: there were two peaks in spring (20.1 %) and autumn (18.3 %). In summer (12.8 %) and winter (15.1 %) the prevalence of infection was lower. Morphologically, the E. excisus larvae found in roaches were different compared to those found in predatory fishes: they had more pale color and were smaller in length. E. excisus is a prevalent infection of roach in Dnipro-Buh estuary. Considering seemingly increasing prevalence of E.excisus infection, further studies are required to understand a pathophysiology of E.excisus infection in mammals and humans, since data remain limited.