Seals and Trichinella parasites

Trichinella is a roundworm transmitted between humans and animals

Parasites of the Trichinella species are zoonotic roundworms transmitted between people and animals, whose infectious larvae live in the muscle cells of host animals. Infection is acquired by eating raw or undercooked meat containing these larvae. In addition to people, the parasite is transmitted to numerous carnivorous animal species, domestic animals as well as wild ones, terrestrial and marine mammals, and birds and reptiles. There are several species of Trichinella. The various species have different geographic distribution and separate host species. In Finland, trichinellae are regionally very common in wild animals, particularly in foxes, raccoon dogs and lynxes, and the most common species is Trichinella nativa, which has adapted to arctic conditions. Among marine mammals in northern regions, particularly the walrus is a known carrier of Trichinella (primarily T. nativa), and eating walrus meat has caused epidemics of trichinellosis among people in arctic regions. Experimentally, it has been shown that T. nativa is readily transmitted to gray seals. Naturally infected seals have been found in the arctic waters of Greenland, Alaska and Russia.

To monitor trichinellae in seals, meat samples have been acquired from hunted gray seals, and gray seals and ringed seals hunted for scientific purposes. Samples also have been received from seals found dead.

In Finland, the Finnish Food Safety Authority Evira monitors the presence of trichinellae in wild animals. Monitoring of the situation of Trichinella among seals is done in co-operation with the Finnish Game and Fisheries Research Institute.

Legislation on meat inspections requires the inspection of carcasses of wild game, e.g. seals, if the meat of these is to be processed in meat plants or otherwise delivered to general consumption. Inspections of meat of seals always comprise analysis for Trichinella larvae. In cases of finding these parasites, the carcass will be discarded and its meat must not be used as food. In practice, seal meat rarely is delivered to Finnish meat plants.

Additional information:

Researcher Marja Isomursu, Evira, firstname.lastname@evira.fi

Researcher Mervi Kunnasranta, RKTL, firstname.lastname@rktl.fi

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