Sealworm common in Swedish cod fillets: study

Sealworm is common in fillets of cod and short-spined sea scorpions in the Baltic Sea, local media reported on Monday, citing studies from the Swedish University of Agricultural Sciences.

Researchers examined fish fillets from more than 2,000 cods and short-spined sea scorpions caught in the Baltic Sea and along the Swedish west coast, and they found fish caught along the southern coast of Sweden were most affected, with the parasite found in more than 60 percent of the cods and up to 100 percent of the short-spined sea scorpions in some areas, daily newspaper Goteborgsposten reported.

The prevalence was the highest in the vicinity of seal colonies, the university said in a press release.

Further north in the Baltic Sea, the occurrence of sealworm was not as common as in areas where seals were numerous.

What limits its spread in the northern parts of the Baltic Sea is still unknown.

"That is something we will examine closer now," said leading researcher Sven-Gunnar Lunneryd.

In order to prevent consumers from rejecting the fish, it was important to inform about the prevalence of sealworm and how the raw fish product should be handled, according to the researchers.

The seal is the final host for the parasitic worm that lives in fish during part of its life cycle. The worm grows to about 4 centimetres long and can be seen in the fish fillets.

The worm affects the fishing industry as the occurrence of worm lessens the value of the fish. Humans will commonly have allergic reactions to the worm, and become sick in serious cases, if they consume worm-infested fish raw.