title: Microhabitat preference of Anisakis simplex in three salmonid species: immunological implications.
abstract: Three salmonid fish species, Oncorhynchus mykiss, Salmo salar and Salmo trutta, were infected experimentally with the parasitic nematode Anisakis simplex (A. simplex) and the difference between in vivo behaviour of the nematode in the three fish species was investigated. Infection success rate differed between species. S. salar (Baltic salmon) showed the highest number of successfully established nematodes, whereas S. trutta (brown trout) and O. mykiss (rainbow trout) had a higher natural resistance. Microhabitat selection of nematodes differed according to fish species. In brown trout, A. simplex larvae were attached to the digestive tract (stomach, pyloric caeca, intestine), while the majority of larvae found in rainbow trout were located between the pyloric caeca. In Baltic salmon, nematodes were dispersed in and on spleen, head kidney, liver, swim bladder and musculature. Encapsulation and inflammatory cellular reactions differed accordingly. Histopathological and immunohistochemical studies using monoclonal antibodies raised against salmonid IgM, CD8 and MHCII were performed to detect the presence of immune cells around the infecting nematodes. None of the three fish species showed positive reactions for IgM-bearing cells in the inflammatory tissue connected with nematodes. CD8+ cells were detected in all three species and MHCII-bearing cells were found associated with encapsulated A. simplex in rainbow trout and brown trout, but not in Baltic salmon. Physiological, immunological and pathological implications of microhabitat differences are discussed.
authors.affiliation: Laboratory of Aquatic Pathobiology, Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg C, Denmark. qusay@life.ku.dk
authors.forename: Qusay Z M
authors.initials: QZ
authors.lastname: Bahlool
authors.forename: Alf
authors.initials: A
authors.lastname: Skovgaard
authors.forename: Per
authors.initials: P
authors.lastname: Kania
authors.forename: Simon
authors.initials: S
authors.lastname: Haarder
authors.forename: Kurt
authors.initials: K
authors.lastname: Buchmann
mesh_terms: D000818:Animals; D017129:Anisakiasis / Q000469:parasitology / Q000662:veterinary*; D017163:Anisakis / Q000145:classification / Q000502:physiology*; D005393:Fish Diseases / Q000469:parasitology*; D007814:Larva / Q000145:classification / Q000502:physiology; D012487:Salmonidae; D013045:Species Specificity