First record of Pseudoterranova decipiens in sprat (Sprattus sprattus) from the Baltic Sea

A dispersion of Anisakidae nematodes (particularly Contracaecum osculatum) among marine organisms in the Baltic Sea has been reported over the last decade. This is in line with an increase in the number of grey seal that act as final host for Contracaecum osculatum and Pseudoterranova sp., and are thus indispensable for the completion of their life cycles. Most attention has been paid to zoonotic nematode species, like Pseudoterranova sp., which have been noted in commercially important fish in the area. Little is known about the spread and transmission of Pseudoterranova sp. in the Baltic Sea. The aim of this study was to investigate whether sprat may play a role as a transport host for this Anisakidae. Samples were collected in three areas of the southern Baltic Sea (south and east of Bornholm, Słupsk Farrow and the Gulf of Gdańsk) during a research cruise in August 2019. A visual inspection of the viscera of 556 sprats was conducted. Parasites were identified using anatomomorphological and molecular methods. Nematodes were recorded only in sprat caught southeast of Bornholm (prevalence 2.7%; intensity of infection 1-4; abundance 0.05). Molecular identification revealed the presence of Pseudoterranova decipiens. This is the first report of P. decipiens in sprat from the Baltic Sea. Sprat is likely a transmitter of P. decipiens in the Baltic Sea food web.