I am in charge of the parasitology research and advisory activities which are integrated in the institute’s section of contaminants and biohazards. My research activities mainly focus on the occurrence and distribution in time and space, of potentially consumer hazardous or quality-reducing parasites in the commercially most important marine food fish stocks in Norway, including herring, mackerel and cod. Besides the food safety and hygienic aspects, I am particularly interested in studying the mechanisms or possible patterns that determine both level of infection and spatial distribution of the actual parasites in different fish species and ecosystems.
Parasites of seafood safety concern
Certain parasites, especially the larvae of anisakid roundworms (nematodes), are common in so to speak every marine fish species from all European fishing grounds. The parasite species of primary concern is Anisakis simplex , also known as the herring- or whale worm. If live Anisakis larvae are accidentally ingested by man, they may penetrate the gut wall and cause acute inflammation, a condition known as anisakidosis. However, the disease seems to be very rare in northern Europe as raw or undercooked fish is usually not on the Norwegian menu. While most of the Anisakis -larvae – regardless of host species – seem to lodge in or on the organs of the abdominal cavity of fish, some worms may migrate into the fish flesh, sometimes even deeply into the fillets. This behaviour, which makes both detection and removal of the parasites more difficult, is to blame for the attention the worms receive from consumers and public food safety authorities. Moreover, larval occurrence in terms of their abundance and within-fish distribution largely depends on fish host species and their respective feeding behaviour. Thus, fish that prey on other fish such as hake and cod, are usually more heavily infected with anisakid larvae compared to strict plankton feeders such as capelin. However, we only know little about the spatial distribution of anisakid larvae in various economically important fish species, i.e. whether or not the larvae occur in the fillets of the actual fish species.
Self-control programmes in the fish industry are hampered by the fact that the epidemiology of fish nematode parasites in European markets is not well-understood. The collection of systematic data on the complete life cycle, geographical and seasonal distribution, prevalence, intensity, and anatomical location of parasites of public health importance in wild caught stocks and fishery products is currently made on biased and opportunistic bases, with no time-series available nor any monitoring programs coordinated on a pan-European scale. A well designed systematic epidemiological survey of the ten economically most important fish species or stocks from four major fishing areas aims to provide the basis for analysing and modelling parasite prevalence. Besides the large scale of the survey in terms of geographical and temporal range as well as sample size and number of host species, an important advantage will be the use of the same nematode detection method by all surveyors to map the infection level and spatial distribution of anisakid larvae in the target fish species and fishing areas.
Levsen A. & Karl H. (2014). Anisakis simplex (s.l.) in Grey gurnard ( Eutrigla gurnardus ) from the North Sea: Food safety considerations in relation to fishing ground and distribution in the flesh. Food Control 36: 15-19.
Levsen A. & Lunestad B.T. (2010). Anisakis simplex 3 rd stage larvae in Norwegian spring-spawning herring ( Clupea harengus L.), with emphasis on larval distribution in the flesh . Veterinary Parasitology 171: 247-253.
Levsen A. , Jørgensen A. & Mo T.A. (2008). Occurrence of postmortem myoliquefactive kudoosis in Atlantic mackerel, Scomber scombrus L., from the North Sea. Journal of Fish Diseases 31: 601-611.
- Survival of Anisakis in dried cod
- Anisakis (nematodes) in rainbow trout
- Investigating salt tolerance of nematodes (Anisakis)
- Surveillance of the Norwegian wild-catch fisheries for biohazards and contaminants
- Nationwide surveillance of Norwegian farmed salmon for parasitic nematodes
- Abundance of possibly human hazardous parasites in fish bound for EU markets
Fish feed as source of potentially allergenic peptides from the fish parasite Anisakis simplex (s.l.)Animal Feed Science and Technology; Volum 202. S. 52-61
- År: 2015
Microbiological assessment along the fish production chain of the Norwegian pelagic fisheries sector - Results from a spot sampling programmeFood microbiology (Print); Volum 51. S. 144-153
- År: 2015
Anisakid nematodes in beaked redfish (Sebastes mentella) from three fishing grounds in the North Atlantic, with special notes on distribution in the fish musculatureVeterinary parasitology; Volum 207.(1-2) S. 72-80
- År: 2015
Anisakis simplex (s.l.) in Grey gurnard (Eutrigla gurnardus) from the North Sea: Food safety considerations in relation to fishing ground and distribution in the fleshFood Control; Volum 36.(1) S. 15-19
- År: 2014
Effect of Anisakis simplex (sl) larvae on the spoilage rate and shelf-life of fish mince products under laboratory conditionsFood Control; Volum 46. S. 121-126
- År: 2014
The role of muscle-invading anisakid larvae on bacterial contamination of the flesh of post-harvest blue whiting (Micromesistius poutassou)Food Control; Volum 30.(2) S. 526-530
- År: 2013
IgE sensitization to the fish parasite Anisakis simplex in a Norwegian population: A pilot studyScandinavian Journal of Immunology; Volum 75.(4) S. 431-435
- År: 2012
A quantitative sandwich ELISA for the detection of Anisakis simplex protein in seafoodEuropean Food Research and Technology; Volum 232.(1) S. 157-166
- År: 2011
Occurrence and distribution of anisakid nematodes in Grey gurnard (Eutrigla gumardus L.) from the North SeaFood Control; Volum 22.(10) S. 1634-1638
- År: 2011
Some Haliotrema (Monogenea: Dactylogyridae) from Cultured Grouper (Epinephelus spp.) with Emphasis on the Phylogenetic Position of Haliotrema cromileptisJournal of Parasitology; Volum 96.(1) S. 30-39
- År: 2010
Anisakis simplex third stage larvae in Norwegian spring spawning herring (Clupea harengus L.), with emphasis on larval distribution in the fleshVeterinary parasitology; Volum 171.(3-4) S. 247-253
- År: 2010
Occurrence of postmortem myoliquefactive kudoosis in Atlantic mackerel, Scomber scombrus L., from the North SeaJournal of Fish Diseases; Volum 31.(8) S. 601-611
- År: 2008
De vanligste infeksjoner hos importert akvariefisk - en mulig trussel mot norsk faunaNorsk Veterinærtidsskrift; Volum 115. S. 639-649
- År: 2003