Evaluation of the good quality and parasitic purity of fish from lake Ladoga

Freshwater fish is one of the most valuable resources of inland waters. Raw fish is a perishable product, therefore, the assessment of product freshness is the most important indicator of its safety. In addition, in relation to freshwater fish, the indicator of parasitic purity is of particular importance, since fish is an intermediate host of pathogens of parasitic diseases transmitted to humans.The studies were carried out in the summerautumn period. The objects of research were samples of chilled freshly caught fish from the southern part of Lake Ladoga. Veterinary and sanitary examination of fish was carried out in accordance with the Veterinary Rules for the appointment and conduct of veterinary and sanitary examination of fish, aquatic invertebrates and fish products from them intended for processing and sale by organoleptic, physicochemical and microscopic methods. Parasitological examination included external examination, parasitological dissection of the fish, examination of muscle tissue by the method of parallel cuts and compressor. As a result, the studied samples were recognized as fresh in terms of organoleptic, physicochemical and microscopic parameters. An external examination of the eyes revealed damage to the lens of the eye by metacercariae of trematodes Diplostomum sp., gill filaments of roach were affected by monogenetic flukes Dactylogyrus sp. Pigmented areas of localization of Posthodiplostomum cuticola metacercariae, the so-called «black-spotted disease», were noted on the surface of the body of fish of the cyprinid family.
During parasitological autopsy and examination of the abdominal cavity, the surface of the internal organs of the bream, the larva of Ligula intestinalis was found, and the plerocercoids of Diphyllobothrium latum were found in the caviar of two individuals of the pike. As a result of a compressor study of the muscle tissue of pike, crucian carp, roach, rudd, perch, and bream, Paracoenogonimus ovatus metacercariae were identified. Of the parasites found in the samples of the studied fish, D. latum is of epidemiological significance, the rest of the pathogens are not dangerous to humans, the sanitary assessment of the fish should be given on the basis of the presentation of the product.

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