The nematode parasites of this family differ from others as their complex life cycle needs several stages (usually four) before completing their life cycles in the final host i.e. a fish. It is passed on when an infected fish is eaten by a large marine mammal. If infected fish are caught, and eaten raw or undercooked, they can even affect humans. In Japan and today other countries the growing popularity of Sushi, Sashimi, Ceviche and Gravlax, makes it vital to be aware of the possible risks. Freezing raw fish at -20 C for a minima of 8 days will theoretically ensure the eradication of the parasite, however many home deep freezers will not reach this degree of coldness. In Japan the population as well as virtually all restaurateurs are aware of the risks, so cases of infection are very rare as all fish are treated by freezing, preservation techniques, etc. before being consumed.
The prognoses vary with host, parasite, the tissue site infected, as well as the intensity of infection. The greater the intensity of infection, the more unfavourable the prognosis.
Because of the highly complex life cycle no prophylactic techniques are known
Dr. Hauck, Kent
Utah Dept. of Aquaculture
Salt Lake City UT. USA