Possibility of anisakid larvae infection in farmed salmon

SUMMARY: Nematodes belonging to the family Anisakidae including Anisakis simplex and Pseudoterranova decipiens are known to cause anisakiasis when their live larvae are ingested by humans. We estimated the possibility of anisakid infection to salmonids, farmed in sea net-pens at Onagawa Bay, Miyagi, Japan, in 1992, 1998 and 1999, by direct examination of the edible muscle and examination of the contents of the alimentary canal. From direct examination of the muscle, no nematode was found in the 249 farmed coho salmon Oncorhynchus kisutch and 40 farmed rainbow trout Oncorhynchus mykiss . In contrast, third-stage larvae of Anisakis simplex were found in seven of 14 wild coho salmon caught in Russia and all the 40 wild chum salmon Oncorhynchus keta caught at Nemuro and Kesennuma in 1998. The stomach and intestines of 521 farmed coho salmon and 40 farmed rainbow trout were examined carefully for the existence of possible carrier organisms such as crustaceans, fish or squid. Such carrier organisms were not found in the stomach and intestines of farmed fish. Thus, we conclude that the possibility of anisakid infection is very low in farmed salmonids.