Search

Blue mussels, Mytilus edulis, serve as second intermediate hosts for several trematode species, but little is known about the mechanisms underlying parasite infections in mussels. To reveal these mechanisms, the prevalence and intensity of trematode larvae (metacercariae in species of Gymnophallus, Himasthla and Renicola) were examined in blue mussels at 19 intertidal sites from the North Atlantic (Ireland, Iceland, Norway) to the Arctic Ocean (north-western Russia). Mussel samples were taken in 2005-2008. The impact of a number of environmental (maximal sea surface temperature, SSTmax) and biological factors (mussel age and density and the abundance of avian final hosts) on trematode infection was examined. Infection levels correlated with the interaction between local bird abundance and mussel age and density. They increased with mussel age but their dependence on mussel density and bird abundance varied among parasite genera. Prevalence and intensity increased with SSTmax for Renicola spp., but no relationship was found for Gymnophallus and Himasthla spp. The ambiguous effect of SSTmax is likely explained by the broad range of optimal temperatures for the normal functioning of trematode larvae (cercariae) infective for mussels and by the high dependence of the level of mussel infection on a combination of local ecological factors. High infection levels were observed even in localities with a low SSTmax. No mussels were infected in the most northeastern population, probably due to extreme conditions in the Arctic intertidal preventing trematode transmission. Future warming of the Arctic may accelerate trematode transmission in this system., Introduction Parasites, which may strongly influence the composition, structure and dynamics of their hosts' populations (reviewed by Combes 2001; Marcogliese 2005; Poulin 2007; Thomas et al. 2009), dramatically affect marine [...]

During 2004-2020 in total 18 anisakid larvae (Nematoda) were sent in to the Laboratory of Parasitology at Keldur for investigation and species identification. Fourteen had temporarily lived within the human body and were alive when detected, three were noticed alive in food just before being consumed, one larva was found dead. Pseudoterranova decipiens was found í 16 instances (89%), Anisakis simplex in two (11%). The one Anisakis case was a wriggling larva detected in the diaper of a baby that was believed to have ingested the larva with undercooked fish three days earlier in the kindergarten. In the other case a dead larva was found entangled in fish chew, spit out by a baby being fed with boiled haddock. Pseudoterranova larvae in humans (n=13) were most frequently detected in the mouth (11 persons). In one instance winding movements of larva in vomit of a baby attracted the attention of the mother, in another case a person detected tickling movements of a larva when cleaning the anal area after defecation. Length of the 13 Pseudoterranova larvae varied between 30 and 47 mm. They were believed to have lived in their hosts from one up to nine days. Nine larvae had already developed to the L4, stage, four were still in the L3 stage. Cod was the most frequently mentioned source of infection (5 of 14 cases), two persons regarded catfish to be the culprit, one named both fish species. In one case either sushi or plaice was believed to be the infection source, one person presumably got the larva participating in a sushi feast. In four cases the fish source remained unknown. Most often the larva was consumed in private homes, three persons believed to have gotten the larva when dining in a restaurant, a harbour worker got the worm when eating raw fish and the same baby got a larva on two different occasions in the kindergarten.