Food safety hazards that occur during the production stage: challenges for fish farming and the fishing industry.

Seafood derived from wild fish as well as farmed fish has always been an important source of protein in the human diet. On a global scale, fish and fish products are the most important source of protein and it is estimated that more than 30% of fish for human consumption comes from aquaculture. The first part of this paper outlines the hazards and challenges associated with handling fish during farming and capture. The authors describe infectious agents that cause disease in fish as well as humans, zoonotic agents, intoxications due to bacteria and allergies caused by the consumption of fish. Although only a few infectious agents in fish are able to infect humans, some exceptions exist that may result in fatalities. However, the greatest risk to human health is due to the consumption of raw or insufficiently processed fish and fish products. The second part of the paper considers environmental contaminants in seafood that may pose a risk to human health, such as medicinal products and residues associated with aquaculture, persistent lipophilic organic compounds and metals (methyl-mercury, organotin). The authors include an updated overview of the various factors associated with farmed and captured fish that may cause risks to human health after consumption. Moreover, they discuss the challenges (in the widest sense) associated with handling fish during capture and farming, as well as those encountered during processing.

Immune response to a recombinant capsid protein of striped jack nervous necrosis virus (SJNNV) in turbot Scophthalmus maximus and Atlantic halibut Hippoglossus hippoglossus, and evaluation of a vaccine against SJNNV.

Immunisation by intraperitoneal injection of an oil-emulgated recombinant partial capsid protein (rT2) from striped jack nervous necrosis virus (SJNNV) was performed on adult turbot Scophthalmus maximus and Atlantic halibut Hippoglossus hippoglossus. A specific humoral immune response was recorded in both species, and the levels of rT2-specific antibodies increased markedly in all groups during the 20 wk experiment. A challenge model for SJNNV was established by intramuscular injection of juvenile turbot. The turbot developed viral encephalopathy and retinopathy (VER), also known as viral nervous necrosis (VNN), with cumulative mortality in the range of 25 to 66%, after intramuscular inoculation with SJNNV propagated in the striped snake head cell line (SSN-1). Although neither clinical signs nor mortality were registered, SJNNV was neuroinvasive after bath exposure. The infection after both modes of challenge was verified by means of immunohistochemistry and RT-PCR, and SJNNV was reisolated in cell culture. The results indicate that SJNNV may have entered the central nervous system (CNS) by axonal transport through motor nerves after intramuscular inoculation. A vaccine efficacy test was performed on juvenile turbot, employing oil emulsified rT2 as a test vaccine and intramuscular inoculation of SJNNV. Significant protection was observed when the challenge was performed 10 wk post-vaccination.

Efficacy of orally administered oxolinic acid and Vetoquinol, an oxolinic acid ester, for the treatment of furunculosis in Atlantic salmon Salmo salar held in seawater.

This study was performed to determine the efficacy of orally administered oxolinic acid and Vetoquinol, an oxolinic acid ester, in the treatment of experimental induced furunculosis in Atlantic salmon Salmo salar held in seawater. Two strains of the causative bacterium Aeromonas salmonicida subsp. salmonicida, 1 sensitive (VI-88/09/03175) and 1 resistant (3475/90) to oxolinic acid, were used. In 2 trials, cohabitational challenges were performed by introducing 8 fish challenged in advance by an intraperitoneal injection of 2.2 x 10(4) colony forming units of strain 3475/90 (Trial 1) or strain VI-88/09/03175 (Trial 2) to 10 aquaria each containing 40 healthy fish. The treatment groups in both trials consisted of 4 groups receiving either oxolinic acid (2 groups) or Vetoquinol (2 groups) and 1 control group. An unchallenged, unmedicated group was used to determine the natural mortality in the population. The recommended therapeutic dose of 25 mg oxolinic acid kg-1 fish at Days 1, 2, 4, 6, 8 and 10 following initiation of treatment was used. Oral medication initiated at Day 10 (Trial 1) or Day 11 (Trial 2) following challenge significantly (p < 0.05) lowered the specific mortality in all drug-treated groups compared to the untreated control groups. Mortality in Vetoquinol-treated groups was significantly (p < 0.05) lower than in oxolinic acid-treated groups in Trial 1 whereas no significant (p < 0.05) difference in survival rate was found between the medicated groups in Trial 2.

Stability of an infectious pancreatic necrosis virus (IPNV) isolate stored under different laboratory conditions.

An infectious pancreatic necrosis virus (IPNV) belonging to the Sp serotype, isolated from scallops Pecten maximus, was propagated and suspended in sterile water and cell culture medium with different salinities and incubated at temperatures ranging from -80 to 40 degrees C. Virus stability was examined by measuring virus titers under different storage conditions. Virus titers were also measured after repeated freezing and thawing, and in incubated sterile filtered scallop hepatopancreas, haemolymph and crystalline style samples, and salmon Salmo salar kidney homogenate. The virus was stable under most storage conditions. Temperatures ranging from -80 to +20 degrees C, as well as salinities from 0 to 40/1000, did not seem to influence the stability of the virus. A reduction was observed above 20 degrees C. Each freezing and thawing procedure resulted in a reduction of the virus titer. This reduction was larger at -80 than at -20 degrees C. The IPNV persisted for a long period in sterile filtered scallop haemolymph, dissolved crystalline style and hepatopancreas. In kidney homogenate from IPNV-infected salmon the virus titers were reduced at least 10-fold during the first day of incubation at all temperatures tested. When virus was propagated in cell culture and subsequently mixed with non-infected salmon kidney homogenate, the virus proved more persistent. Our results illustrate the importance of rapid and standardised laboratory processing of potentially virus-containing tissue samples, and are relevant when considering laboratory storage of samples containing IPNV.

Decreased concentration of hemoglobin, accumulation of lipid oxidation products and unchanged skeletal muscle in Atlantic salmon (Salmo salar) fed low dietary vitamin E.

Atlantic salmon (Salmo salar) fry, initial weight 0.16 g, were fed a semipurified diet with 0, 15, 30, 60 or 120 mg dl-α-tocopheryl acetate/kg. After 24 weeks, the first two of these groups were extinct, and the fish receiving 30 mg/kg were clearly vitamin E deficient. Vitamin E deficient fish had low hemoglobin levels, characterized by a combination of reduced cellular hemoglobin concentration, red cell volume and red cell number, and an increased number and fraction of immature red blood cells. The hemoglobin concentration decreased over the decreasing range of experimental dl-ga-tocopheryl acetate levels. Therefore, even if 60 mg dl-α-tocopheryl acetate/kg gave good survival, this level was clearly physiologically suboptimal. Ceroid accumulated in the liver of fish fed 30 mg vitamin E/kg, and autofluorescent inclusions were found in the red blood cells of fish fed 30 and 60 mg vitamin E/kg. Degeneration of skeletal muscle was not observed in the present study.

Kinetics of the binding of immunoglobulins, antibodies and virus haemagglutination inhibitors to kaolin.

Kaolin is widely used in diagnostic virology, mainly to remove serum lipoproteins that may interfere with antibody assaying. The binding kinetics of antibody to kaolin at different pH values and with varying amounts of kaolin indicated a uniform and characteristic binding pattern for IgG with maximum adsorption at pH 5 and no adsorption at pH above 9. To avoid loss of IgG antibody adsorption with kaolin should therefore be performed at pH greater than or equal to 9. The amount adsorbed increased with the amount of kaolin used. The IgM pattern was less uniform with maximum adsorption of total IgM at about 7.0, the amount adsorbed being highly dependent on kaolin concentration. Serum lipoproteins were rapidly and strongly adsorbed independent of pH from 7 to 11 and independent of the lipoprotein content of the serum. The amount of kaolin used was, however, critical.

Heterogeneity in the reactivity of various groups of IgM antibodies with kaolin.

Kaolin strongly adsorbed rheumatoid factor (RF) and mono-nucleosis antibodies, while cold agglutinins and some antimicrobial IgM antibodies were poorly adsorbed. Maximum adsorption took place at a pH of about 7. The degree of adsorption also depended on the amount of kaolin. Rheumatoid factor could be eluted from kaolin at pH 11 after adsorption at pH 7. The reported heterogeneity with regard to reactivity with kaolin is suggested to be due to hydrophobic interactions.