Prevalence of anisakin nematodes in fish from Southern Baltic Sea

Nematodes from the superfamily Ascaridoidea (families Anisakidae and Raphidascarididae) are worldwide distributed parasites. Their live cycles include many species of water invertebrates and teleostean fish as intermediate hosts, and fish, sea mammals or fish-eating birds being definitive hosts. Humans can be infected with some of these parasites after consumption of raw or wrongly processed fish. The parasitological investigations of fish (herring, cod and flatfish) from southern Baltic (ICES 24-26) provided in the years 80 and 90 showed their infection with larvae of several anisakid species: Anisakis simplex s. str., Contracaecum osculatum C and Hysterothylacium auctum. Sporadically Pseudoterranova decipiens and Raphidascaris acus were also found. Larvae of Anisakis simplex were noted mainly in herrings, C. osculatum primarily in cods and H. auctum in flounders. Additionally, preserved herrings (marinated, smoked) were also investigated and sporadically live larvae of A. simplex were found. The main etiological agent of human anisakidosis worldwide is A. simplex. Although the live cycle of this nematode cannot be completed in the Baltic Sea--this nematode is brought to the Baltic by infected herring migrating from the North Sea for spawning in coastal waters of the Southern Baltic--the prevalence and intensity of infection with larvae of this nematode species were the highest in fish investigated by us. The results obtained suggest the possibility of the human infection with A. simplex larvae in Poland.