How effective is freezing at killing Anisakis simplex, Pseudoterranova krabbei, and P. decipiens larvae? An experimental evaluation of time-temperature conditions

Abstract

The consumption of raw or inadequately cooked marine fish can lead to several disorders caused by the ingestion of viable anisakid nematodes. Although anisakid larvae can be killed by subzero temperatures, making freezing an important control measure for this potential health hazard, these parasites can survive freezing under some conditions. Therefore, the aim of the present study was to experimentally evaluate the time-temperature conditions needed to kill Anisakis simplex and Pseudoterranova spp. The effectiveness of freezing was tested on two species of fish: cod, Gadus morhua from the North Atlantic, and herring, Clupea harengus membras from the southern Baltic Sea. Samples, which comprised skinless fillets of cod ( n = 40) with visible parasites and whole herring ( n = 240), were separately frozen at − 15, − 18, or − 20 °C for 24 h, or at − 20 °C for 48 h in the single-compressor freezer and at − 20, − 25, or − 35 °C for 24 h in the double-compressor freezer. After thawing, parasites were stained with malachite green and examined under the microscope for viability. All A. simplex and Pseudoterranova spp. larvae in cod fillets died at a temperature of − 15 °C or lower. However, freezing did not kill all the A. simplex larvae in whole herring: spontaneous movement of these parasites was observed in samples stored in the single-compressor freezer at − 15, − 18, and − 20 °C over 24 h. Our results demonstrate that the freezing procedure must consider both the capability of the freezing device and the nature of the fish product to ensure consumer safety.

Advances in Omic Studies Drive Discoveries in the Biology of Anisakid Nematodes

“…Improving molecular knowledge on this family of parasites may be helpful in several ways, spanning from basic research to clinical and public health applications. These are mostly related to: (i) food-safety, given the presence of infective larvae in food products [ 26 , 27 ]; (ii) allergy-mediated diseases, even in relation to work exposure or to potential therapeutic use of parasitic derived products [ 28 ]; and (iii) the understanding of carcinogenic processes in relation to nematode infection [ 29 ].…”

Genera and Species of the Anisakidae Family and Their Geographical Distribution

“…decipiens [ 43 ] and P . krabbei [ 110 ]. While the term “anisakiosis” refers to the pathology caused specifically by the species Anisakis simplex s.s. [ 7 , 14 , 15 , 19 , 20 , 52 , 89 ].…”

Development and Application of Novel Chemiluminescence Immunoassays for Highly Sensitive Detection of Anisakis simplex Proteins in Thermally Processed Seafood

“…To prevent anisakiasis, many countries, such as countries in the European Union (EU), United States of America (USA), and Canada, require the freezing of raw fish before placing on the market or other processing to kill viable parasite larvae [ 10 ]. However, it should be emphasized that, according to the published studies, single A. simplex larvae can survive at −20 °C for 24 h [ 10 ] and, according to other studies, even up to 60 h [ 11 ].…”

“…To prevent anisakiasis, many countries, such as countries in the European Union (EU), United States of America (USA), and Canada, require the freezing of raw fish before placing on the market or other processing to kill viable parasite larvae [ 10 ]. However, it should be emphasized that, according to the published studies, single A. simplex larvae can survive at −20 °C for 24 h [ 10 ] and, according to other studies, even up to 60 h [ 11 ]. Interestingly, Sanchez-Alonso et al [ 12 ] showed that A. simplex L3 larvae during freezing release more allergens than the larvae not exposed to low temperatures, which can increase the allergic potential of frozen seafood containing Anisakis .…”