Infestation of Black Sea-Caspian Sprat (Clupeonella Cultriventris) with Cestodes of the Genus Proteocephalus in the Kama Reservoir and Histological Examination of Fish Intestines Infested with These Parasites

Introduction. The Black Sea-Caspian sprat (Clupeonella cultriventris) is an alien species adapted to the Kama Reservoir conditions, capable of affecting the trophic relationships in this ecosystem. However, the composition of helminth fauna in this ecosystem and the pathological changes induced by the certain pathogens, such as cestodes of the genus Proteocephalus, are currently poorly investigated. The aim of the study is to investigate the infestation of C. cultriventris with cestodes of the genus Proteocephalus in the Kama Reservoir and to describe the histological changes in the fish intestines caused by this infestation. Materials and Methods. In the autumn-winter period of 2024, the C. cultriventris (n=83) were taken from the several parts of the Kama Reservoir. A partial biological analysis, partial helminthological dissection and histological examination of the intestines infested with cestodes were carried out. Parasitological examination was performed at the Department of Infectious Diseases of Perm State Agro-Technological University. Preparation of histological specimens was performed in the histopathology laboratory of Perm Regional Children’s Clinical Hospital. The prepared histological sections were scanned using the Vision Assist automated system and Vision microscopy automation software. Mathematical processing of the obtained data was performed in Microsoft Excel. Results. The highest infestation extensity (IE 50%) of Proteocephalus sp. (juv) corresponding to infestation intensity (II) range 1–2 was observed in sprat form the middle part of the Kama Reservoir; in sprat from the upper part, it was several times less (IE 13% corresponding to II range 1–3); sprat from the lower part was not infested at all. The size and weight parameters in sprat from the upper and lower parts of the Reservoir were significantly higher than that in the fish from the middle part — approximately 2 times exceedance in weight and 1.2 times — in length. Histological examination of sprat intestines revealed changes in mucosa and submucosa layers; the epithelium was in a state of desquamation, the stromal state of the villi was loose and edematous. Discussion and Conclusions. Data on infestation of C. cultriventris with the cestodes of the genus Proteocephalus sp. in the Kama Reservoir are presented for the first time. It has been revealed that cestode infestation affects the biological parameters of fish and causes minor inflammatory pathological changes in the intestines. Detection of the pre-mature cestodes in the non-specific hosts is not enough factor for their identification, therefore, further research is needed to clarify the host-parasite relationships of C. cultriventris and Proteocephalus sp.