Fish Invasion with Eustrongylides Excisus (Nematoda: Dioctophymatidae) in the Don River Delta

Eustrongylides spp. are cosmopolitan parasitic nematodes with several freshwater fish species as intermediate or paratenic hosts, rarely reported as zoonotic agents. This work aims to report about the occurrence of this parasite in specimens of round goby, Neogobius melanostomus (Pallas, 1814), monkey goby, N. fluviatilis (Pallas, 1814), syrman goby, Ponticola syrman (Nordmann, 1840) and 122 specimens of pike-perch, Sander lucioperca, (Linnaeus, 1758) caught in the Don river delta and the eastern part of the Taganrog Bay (southern Russia. Totally 353 specimens of the Azov fish were collected between 2019 and 2022 years in spring. Fish were visually examined, visible parasites were collected and counted after both procedures, and then they were identified to genus level by microscopic examination. The body cavity and serous integument of the intestine are the main places of the localization of parasites for gobies, muscles and the abdominal wall—for pike-perch. A positive trend was noted in the growth of E. excisus fish invasion indices. It is essential to inform the general public about the risks associated with eating raw or undercooked fish. Fish surveillance should be strengthened, especially in the fishing areas.