Infectious dose/dose response: Ingesting one nematode is believed to be sufficient to cause illness, and is the usual number removed from patients (FDA 2003).
Prevalence in seafood: Anisakis simplex has been isolated from many species of fish including: rockfish, herring, cod, halibut, mackerel, wild-caught salmon, yellowfin and skipjack tuna, and squid, from many regions of the world (FDA 2003; Hurst 1984). Reports from Japan include mussels, oysters, crawfish, lobster and prawns as sources of anisakid infections (Durborow 1999).
The rates of infection are often high with 10–90 per cent of samples carrying the parasite (Bouree et al. 1997). Multiple larvae in each fish are also commonly recorded. Table 4.10 lists the incidence and prevalence of A. simplex and other parasites in fish at retail sale around the world.
In Australia A. simplex has been isolated from flathead (Platycephalus speculator), mackerel (Scomberomorus spp.), mackerel tuna (Euthynnus alleteratus), striped trumpeter and farmed salmonids (Ross 2000; Humphrey 1995). It is not known, however, whether the strains isolated were pathogenic to humans.
