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.
The parasite fauna of cod (Gadus morhus) is well described, but the life cycles of Baltic cod parasites are known only in general terms. Invertebrates commonly found in the stomach of cod are recognized as intermediate hosts in the life cycles of nematodes or acanthocephalans. The aim of this study was to determine the source of infection of Baltic cod with parasites found in situ in invertebrates present in the cod stomach. Our results indicate that Saduria entomon is both a source of infection of Baltic cod with parasites and an intermediate host in the life cycle of Hysterothylacium aduncum in the Baltic Sea.
Anisakidae nematodes, especially Contracaecum osculatum, Anisakis simplex, and Pseudoterranova decipiens, have dispersed throughout the Baltic Sea over the last decade. Despite the fact that salmon, Salmo salar, is a popular choice among consumers and therefore one of the most valuable Baltic fish species, information about the level of infection of salmon liver with these zoonotic nematodes is sparse. In 2020, a total of 120 salmon livers were inspected for the presence of parasites showing that 13% of salmon livers were infected with C. osculatum. Furthermore, a single Pseudoterranova sp. larva was detected in one salmon liver, representing a host-parasite system that has never previously been reported in the Baltic Sea.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.