Prevalence of Anisakis Larvae in “Ready-to-cook” Mackerel Fillets Distributed in Mie Prefecture, Central Area of Japan

The prevalence of Anisakis contamination in "ready-to-cook (RTC)" mackerel products distributed in Mie Prefecture, central area of Japan, was examined to assess the risk of anisakiasis. Of 136 mackerel fillets examined, 30 samples (22.1%) were positive for Anisakis larvae. The mackerels caught in the Sea of Japan were higher in frequency of Anisakis contamination (41.4%) compared with those from the Pacific Ocean (7.7%) (p<0.01). Number of Anisakis larvae isolated from RTC mackerel fillets was 169, of which 147 (87.0%) were still alive. Around a half of the Anisakis larvae in mackerel fillets were localized in the mid-part of the abdominal side. Two mackerel species were commonly distributed in Japan, however, Anisakis contamination was mainly observed in Scomber japonicus, but rare in S. australasicus. These findings suggest that the risk of anisakiasis transmitted through RTC mackerels might not be low, however, the risk seems to vary depending on the mackerel species, seasons, fishing grounds, and also distribution of fish products.