title: Resistance against eye flukes: naïve versus previously infected fish.
abstract: A central issue in fish production is the influence of parasitic infections on fish health in fish farms and on survival prospects after fish-stocking into the wild. Is it preferable to produce fish in infection-free conditions or to allow some infection to elicit resistance in fish? We explored the infection of totally naive and previously infected rainbow trout (Oncorhynchus mykiss) by the trematode parasite Diplostomum spathaceum in laboratory conditions. We found that up to 86.1% of the presented cercariae became established in the lenses of naïve fish, which indicated that these fish were highly susceptible to infection and that innate resistance served little or no protection against the parasite. However, acquired resistance after initial infection decreased parasite establishment by 85.0-89.1%. Parasite establishment was also affected by fish host density as fewer parasites were found in fish in higher densities. The implications of these results for the fish-farming industry and fish-stocking protocols are discussed.
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland. anskarv@bytl.jyu.fi
authors.forename: Anssi
authors.initials: A
authors.lastname: Karvonen
authors.forename: Satu
authors.initials: S
authors.lastname: Paukku
authors.forename: Otto
authors.initials: O
authors.lastname: Seppälä
authors.forename: E Tellervo
authors.initials: ET
authors.lastname: Valtonen
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D005123:Eye / Q000469:parasitology*; D005387:Finland; D005393:Fish Diseases / Q000276:immunology*; D005398:Fisheries / Q000592:standards; D016266:Food Parasitology; D007110:Immunity, Active; D017686:Oncorhynchus mykiss; D010986:Platyhelminths; D011156:Population Density; D014201:Trematode Infections / Q000276:immunology / Q000662:veterinary*