A PARASITE which can cause serious health problems if ingested alive has been detected in salmon on the River Tweed.

The discovery has prompted the Tweed Foundation, the scientific and research wing of the River Tweed Commission, to issue guidance to anglers who may wish to eat their own catch or share it with friends and family.

It was while carrying out research tagging on the world-famous fishery at Paxton near Berwick last week, that the Foundation netted four fish with Red Vent Syndrome.

The condition, betraying the presence of the parasitic worm Anisakis and characterised by swollen and bleeding vents, was first reported on Scottish rivers in 2007, but had become less common in recent years.

It is contracted mainly by migrating grilse – young salmon who have spent a single winter at sea – and who become infected from ingested prey.

It cannot be transmitted between fish in fresh water, so anglers are advised it is safe to return infected salmon to the river.

However, last week’s discovery has prompted the Tweed Foundation to re-issue advice from the Food Standards Agency (FSA) which states: “Parasites in fish, particularly Red Vent Syndrome, can if ingested alive, cause serious health problems.” The FSA recommends that all salmon should be visually inspected to detect and remove parasites.

“Those fish which remain obviously contaminated should not be consumed,” states the FSA.

However, the parasites can be destroyed either by freezing the fish at a temperature below -20degreesC for at least 24 hours or by cooking at over 70degreesC for two minutes or more.

“As there is no infallible method of detecting and removing larvae, this advice is particularly relevant for pregnant women and elderly people where ingestion of live parasites from fish can pose a serious health risk,” states the FSA.