Zoonotic nematode larvae in Greenland halibut (Reinhardtius hippoglossoides) from Greenlandic waters: Occurrence, fillet distribution and association with Mushy halibut syndrome

Zoonotic anisakid nematodes commonly infect wild fish, and their presence in commercially caught species represents a consumer hazard due to risk of anisakidosis. The Greenland halibut (GLH) is a species of high commercial value to many countries, including Kalaallit Nunaat (Greenland), where GLH is the second most exported marine species. Despite this, the occurrence of anisakid nematodes in the flesh of GLH remains poorly studied. Additionally, the relationship between anisakid infection and 'Mushy halibut syndrome' (MHS), a condition affecting the fillet quality of GLH, has not been investigated. The aim of this study was to extend our knowledge of the occurrence of anisakid nematodes in GLH, with emphasis on fillet distribution, and explore associations with MHS. GLH (n = 104) from three offshore fishing grounds underwent necropsy and parasitological examination of the main fillet and belly flaps. Overall prevalence of third-stage larval infection was 44.2 %, while mean intensity and abundance were 4.6 and 1.3, respectively. When examining the fillets, third-stage larvae were predominantly found in the belly flaps. For a subsample of fish (n = 55), the investigation included parasitological examination of the body cavity and liver as well as extended necropsy, quality index method assessment and age estimation. The isolated third-stage larvae belonged to three species: <i>Anisakis simplex</i> s. s. was most common (n = 721), followed by <i>Contracaecum osculatum</i> (n = 36). <i>Phocanema bulbosa</i> was found in the body cavity and liver only (n = 11). MHS was associated with higher infection levels in the belly flaps and liver, lower condition factor and higher gonadosomatic index. The results presented here have implications for wild fish stock monitoring and food safety. Recording of the parasite prevalence and distribution in GLH can assist risk management and provide information on the status of the fish species in the ecosystem.