Anisakis spp. in fishery products from Japanese waters: Updated insights on host prevalence and human infection risk factors.

The nematodes of the genus Anisakis are among the most relevant parasitic hazards in fishery products since they are responsible for human infection and allergy cases. In a food safety and epidemiological perspective, several marine hosts from different locations around Japan were examined to characterize the parasitism of Anisakis larvae. Chum salmon (Oncorhynchus keta) and Alaska pollock (Gadus chalcogrammus) showed the highest overall prevalence (100%), followed by blue mackerel (Scomber australasicus) (97.5%), Pacific cod (Gadus macrocephalus) (80%), chub mackerel (Scomber japonicus) (60.1%), Japanese flying squid (Todarodes pacificus) (17%) and Japanese pilchard (Sardinops sagax melanostictus) (2%). In Pacific krill (Euphausia pacifica), apart from one Hysterothylacium aduncum larva, no Anisakis specimens were detected. Anisakis simplex sensu stricto was molecularly identified (PCR-RFLP) for the first time in Japanese flying squid and Japanese pilchard distributed in the Northwestern Pacific ocean. That was the most frequent parasitic species detected followed by A. pegreffii, mostly in the western areas of Japan, hybrid genotypes between the two sibling species as well as A. typica and A. berlandi. Surprisingly, A. simplex s.s. was the most abundant species in one batch of chub mackerel from the East China Sea and A. pegreffii was the main species found in one batch from the Pacific coast of Aomori, which seems to indicate that the ranges of these two sibling species might be more variable than previously thought.