Abstract
Anisakiasis is a gastrointestinal disease caused by infection with anisakid nematodes. Anisakis larvae have been listed as distinct food poisoning agents in the manual of Food Poisoning Statistics, Japan since 2013. The reported numbers of food poisoning cases caused by Anisakis larvae are gradually increasing. A total of 94.0% of the causative larvae species were identified as Anisakis simplex sensu stricto (A. simplex), and 4.4% were identified as Anisakis pegreffii, among human-isolated anisakid nematodes examined in Tokyo Metropolitan Institute of Public Health, Japan from 2011 to 2018. Anisakis species infecting fishes in Japanese waters differ depending on their habitat and depth. A. simplex mainly infects fishes in the Pacific side of Japan, and A. pegreffii mainly infects fishes in the East China Sea and Sea of Japan sides. Regarding the causative foods of anisakiasis, cases by ingestion of mackerel (Scomber spp.) have been the most common in Japan, and cases caused by eating “marinated mackerel” accounted for 32.8% of the total in Tokyo from 2011 to 2017. However, the number of reports of food poisoning caused by skipjack tuna (Katsuwonus pelamis) was highest in May 2018 in Japan. A parasitological surveys of Anisakis third-stage larvae in skipjack tuna in Japanese waters were conducted in 2018 and 2019, and it was confirmed that more A. simplex infections of skipjack tuna may have occurred in 2018 than usual due to the meandering flow of the Black Current. Moreover, a portion of A. simplex larvae migrated from visceral organs to the ventral muscle in live skipjack tuna before capture, suggesting that an extensive cold chain after capture cannot prevent anisakiasis. In fish species that were reported to be high frequency of causative food of anisakiasis, it is necessary to freeze or at least remove the ventral muscle.
Highlights
Introduction food poisoning agents in theManual of Food PoisoningStatistics, Japan, requiring medical doctors to report cases to a public health center
A total of 94.0% of the causative larvae species were identified as Anisakis simplex sensu stricto (A. simplex), and 4.4% were identified as Anisakis pegreffii, among humanisolated anisakid nematodes examined in Tokyo Metropolitan Institute of Public Health, Japan from 2011 to 2018
All the larvae in the ventral muscle were identified as A. simplex. These findings demonstrated, with a portion of A. simplex larvae migrated to the muscle in live skipjack tuna before capture, that an extensive cold chain after capture does not prevent anisakiasis
Summary
Nematodes of the genus Anisakis are parasites, whose definitive hosts are marine mammals such as whales and dolphins, marine fish, and squid. Onset of clinical symptoms in acute gastric anisakiasis cases was reported to occur within 1 to 12 h after the ingestion of infected fish, with peaking at 6 h23). Public Health from 2011 to 2017 showed, among 180 cases (179 gastric anisakiasis cases and an intestinal anisakiasis case), 91.2% (134/147 cases) with clearly known onset timing from the ingestion occurred within 12 h (Table 5) The main symptoms such as abdominal pain (100%), nausea (68.3%), vomiting (39.0%), diarrhea (19.5%), and urticarial (9.8%). It has been reported that A. simplex was detected in 13% of saury’s visceral organs and 1.8% of their muscle tissues[26]) This detection rate was lower than those in mackerel13) and natural salmon27), considering the number of Anisakis food poisoning cases by ingestion of saury, the detection rate in the muscle should not be ignored.
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