National biosecurity approaches, plans and programmes in response to diseases in farmed aquatic animals: evolution, effectiveness and the way forward.

The rapid increase in aquaculture production and trade, and increased attention to the negative effects of disease, are becoming stimuli for developing national biosecurity strategies for farmed fisheries, for which the World Organisation for Animal Health (OIE) Aquatic Animal Health Code and Manual of Diagnostic Tests for Aquatic Animals serve as an excellent framework. Using examples from a few countries and selected diseases, this paper provides a general overview of the development of approaches to implementing biosecurity strategies, including those emerging in the national legislation and regulations of some countries, and those being initiated by industries themselves. The determination of disease status in different epidemiological units (from a farm to a nation), appropriate approaches for preventing the introduction of disease and developing contingencies for disease control and eradication are also discussed. Important to the effectiveness of such strategies are provision of financial, personnel and other resources to implement them, including incentives such as indemnification or compensation in eradication programmes, and practical linkage to regulatory or government policy initiatives.

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.

Science-based assessment of welfare: aquatic animals.

Terrestrial animal welfare has been a matter for exploration for many years. In contrast, approaches towards improving the welfare and humane treatment of aquatic animals are relatively new, as is the thinking behind them. Several issues complicate the process of addressing the welfare of aquatic animals in a consistent manner. These include the following: - the huge diversity among aquatic animals, the majority of which are poikilothermic vertebrates and invertebrates - understanding the practices involved in fisheries, aquaculture and aquatic animal production, and their purpose - the relative paucity of scientific information - understanding the philosophical approaches, policies, guidance and regulations that may influence the provision of optimal welfare and humane practices for aquatic animals. In this paper, the authors attempt to provide an overview of all these elements, relating what is known and understood about these issues for the primary group used in aquaculture and fisheries, finfish, and exploring the factors that may influence the concepts and practices of aquatic animal welfare. These factors seem to be the foundation of all welfare approaches and include: - ethical and moral concepts of animal welfare and humane treatment - whether animals experience suffering from the potentially adverse practices used in their maintenance, management and use - the public and institutional understandings of these issues and their results. These are discussed with the hope that future developments in, and approaches to, aquatic animal welfare will be of use to society, industries and the public.

Bacterial vaccines for fish--an update of the current situation worldwide.

During the last few years, the use of vaccines for disease prevention in aquaculture has expanded both with regard to the number of fish species and number of microbial diseases. According to the responses to a questionnaire received from 41 countries, vaccination is used in the commercial aquaculture of species like Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), sea bass (Dicentrarchus labrax), sea bream (Sparus aurata), barramundi (Lates calcarifer), tilapia (Tilapia spp), turbot (Scophthalmus maximus L.), yellowtail (Seriola quinqueradiata), purplish and gold-striped amberjack (Seriola dumereli), striped jack (Pseudocaranx dentex) and channel catfish (Ictalurus punctatus). The range of bacterial infections for which vaccines are commercially available now comprises classical vibriosis (Listonella anguillarum, Vibrio ordalii), furunculosis (Aeromonas salmonicida subsp. salmonicida), cold-water vibriosis (Vibrio salmonicida), yersiniosis (Yersinia ruckeri), pasteurellosis (Photobacterium damselae supsp. piscicida), edwardsiellosis (Edwardsiella ictaluri), winter ulcer (Moritella viscosa), and streptococcosis/lactococcosis (Streptococcus iniae, Lactococcus garviae). Furthermore, experimental vaccines are used against diseases such as infection with Vibrio harveyi and Photobacterium damsela subsp. damsela in barramundi, piscirickettsiosis and bacterial kidney disease in salmonids, as well as infection with Flexibacter maritimus (now: Tenacibaculum maritimum) in turbot. There was good agreement between the information received from different sources in the same country. Most vaccines are licensed products, but some non-licensed vaccines are also used in commercial fish farms. Most bacterial vaccines are inactivated products and recombinant vaccine technology has so far been used to a very limited extent. Salmonid fish are usually immunised with multivalent vaccines by intraperitoneal injection. In marine fish species vaccination is generally performed by immersion, but use of injection vaccination is increasing, particularly in the Mediterranean region. Only limited use of orally administered fish vaccines is reported. In general, the effect of vaccination against bacterial infections is good. The best protection is obtained with injectable, adjuvanted vaccines. However, injection-site adverse reactions often occur when such products are used.

Traceability of aquatic animals.

Effective methods of traceability are urgently required for use in research as well as in different types of aquaculture operations and to control trade in aquatic animals and products. In regard to the marking of fish, many different tagging methods have been described and the method to be used depends on the purpose and need for tagging. In contrast, for molluscs and crustaceans, only a few methods of marking such animals have been described, due to the practical difficulties. The authors first describe the different methods for tracing fish and fishery products, by means of external tags, such as Floy tags, Carlin tags and passive integrated transponder tags; chemical marking using inorganic substances such as silver nitrate or potassium nitrate, pigments, oxytetracycline, etc.; and several different types of electronic devices in which basic information such as the strain of fish, farm of origin or weight can be stored. Genetic traceability using deoxyribonucleic acid profiling is developing quite rapidly for cultured brood stocks and wild populations. This technique may be used with very high degrees of confidence to assign to or exclude animals or products from their claimed origin, paternity or strain, and may be used as evidence in court proceedings. The second section of this paper describes the traceability of live molluscs for restocking and for human consumption. In these applications, genetic markers have been demonstrated to be suitable. Mechanical tagging on a small scale for research purposes has also been used. Otherwise, the only means of tracing live molluscs are the movement documents and the labelling on boxes that certifies the origin of the commodity. The third section describes the methods available for tracing live and dead crustaceans. A large variety of physical tagging methods for decapod crustaceans is described, such as the injection of biological stains (fast green, Niagara sky blue, trypan red and blue) and external tags such as coloured streamer tags, wire tags and a variety of anchor tags. Furthermore, a number of different internal coding methods, such as the coded micro-wire tags and injected elastomer tags are discussed in detail. As is the case for fish, genetic molecular techniques are also applied in population studies of crustaceans; some of the molecular genetic methods are described. Prawns for human consumption are most frequently packed whole or as tails after the necessary sorting, washing and freezing and the only way of performing a traceback is through documents relating to movement, invoices, health certificates and labelling of the boxes. The minimum requirements for labelling would be the content of the packages, i.e. species, quantity, identification of the manufacturer (name and address), packing place, importer/exporter or vendor of the product, in addition to the loading bill number.

Surveillance of fish diseases in the Nordic countries.

Due to the increasing importance of disease problems in the fish farming industry and the impact disease may have on both feral and farmed fish in the Nordic countries, monitoring and surveillance on diseases have for many years been considered to be of socioeconomic importance. All the Nordic countries have a national legislation as basis for their surveillance and disease control in aquatic animals and regulations listing notifiable diseases of concern to the countries. The list of diseases vary between the countries. In addition, Denmark, Finland and Sweden are ruled by Directive 91/67/EEC as regards placing on the market of aquaculture animals and products. The surveillance for viral diseases in all the Nordic countries has mainly been based on the testing procedures given in the EU Commission Decision 96/240/EC.

Grouping by plasmid profiles of atypical Aeromonas salmonicida isolated from fish, with special reference to salmonid fish.

Plasmid profile analyses were performed for 113 strains of atypical Aeromonas salmonicida and the reference strain A. salmonicida subsp. salmonicida ATCC 14174. The atypical A. salmonicida strains comprised 98 strains obtained from fish originating from 54 farms and 2 lakes in Norway, 10 strains from Canada (2), Denmark (2), Finland (1), Iceland (1) and Sweden (4), the reference strains NCMB 1109 and ATCC 15711 (Haemophilus piscium) of A. salmonicida subsp. achromogenes, and the type cultures A. salmonicida subsp. achromogenes NCMB 1110, A. salmonicida subsp. masoucida ATCC 27013 and A. salmonicida subsp. smithia CCM 4103. A total of 95 strains of atypical A. salmonicida were separated into 7 groups (I to VII) based on the plasmid profiles. Eighteen strains of atypical A. salmonicida had no common plasmid profile. The type strain NCMB 1110 and the reference strain NCMB 1109 were included in group IV, and the type strain ATCC 27013 in group V, but the other reference and type strains had plasmid profiles different from all the other strains. An epidemiological link was documented between strains collected from different farms/localities in each of groups I, III, V and VII. Physiological and biochemical characterizations were performed for 93 of the strains to investigate phenotypic differences between the plasmid groups. Group VII strains and 3 strains with no common plasmid profile differed from the other groups in being catalase-negative. Differences in phenotypic characteristics were shown between the plasmid groups. However, significant variations in reactions for several phenotypic characteristics also occurred within each of the groups I to VII. The present study indicates that plasmid profiling may give useful epidemiological information during outbreaks of atypical A. salmonicida infections in fish. Additional comprehensive phenotypic characterisation is of limited value since the phenotypic characteristics in each plasmid group are not uniform.

Successful aquatic animal disease emergency programmes.

The authors provide examples of emergency programmes which have been successful in eradicating or controlling certain diseases of aquatic animals. The paper is divided into four parts. The first part describes the initial isolation of viral haemorrhagic septicaemia (VHS) virus in North America in the autumn of 1988 from feral adult chinook (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) returning for spawning. The fish disease control policies at both State and Federal levels in the United States of America required quarantine and emergency eradication measures upon the finding of certain exotic fish pathogens, including VHS virus. The procedures for emergency plans, destruction of stocks and disinfection of facilities are described, as well as challenge experiments with the North American strains of VHS virus and the detection of the virus in marine fish species (cod [Gadus macrocephalus] and herring [Clupea harengus pallasi]) in the Pacific Ocean. The second part of the paper outlines the aquatic animal legislation in Great Britain and within the European Union, in regard to contingency plans, initial investigations, action on the suspicion of notifiable disease and action on confirmation of infection. The legal description is followed by an account of an outbreak of viral haemorrhagic septicaemia in turbot (Scophthalmus maximus) in Great Britain, including the stamping-out process at the affected farm and investigations conducted to screen other farms in the vicinity for possible infection. The third part provides a historical review of the build-up of infectious salmon anaemia (ISA) in Norway and the attempts to control the disease using legal measures in the absence of detailed knowledge of the aetiology, epizootiology, pathogenesis, etc. of the disease. The measures taken show that the spread of ISA can be controlled using restrictions on the movement of fish, disinfection procedures, etc. However, acceptance and understanding of the chosen strategy by the fish farmers is a pre-requisite to reach that goal. Finally, the paper summarises future needs for national and international legislation, including the development of standard approaches for control, the creation of appropriate infrastructures and a better understanding of the epidemiology of aquatic animal diseases.

Preparation and applications of the International Aquatic Animal Health Code and Diagnostic Manual for Aquatic Animal Diseases of the Office International des Epizooties.

The Office International des Epizooties (OIE) has recently prepared an International Aquatic Animal Health Code, based on the principles set out in the corresponding OIE International Animal Health Code for terrestrial animals. The principal aim of the Code and the companion Diagnostic Manual for Aquatic Animal Diseases is to harmonise health guarantees for international trade in aquatic animals (fish, molluscs, crustaceans) and aquatic animal products, and to guide state Veterinary Services and/or other competent authorities in the preparation of appropriate health certificates. The Aquatic Animal Health Code and Manual provide detailed information on definitions, notifications, ethics in connection with certification, import risk analysis and import/export procedures. By these means, the preparation of international health certificates can be based on a uniform approach to health control in aquatic animal populations, using the standardised methods described in the Diagnostic Manual. In general, health certification under the Aquatic Animal Health Code is required only for diseases notifiable to the OIE. In addition to such notifiable diseases, however, the Code establishes a list of other significant diseases which need consideration. The listed diseases are recognised as serious transmissible diseases of socio-economic and/or public health importance, in relation to which the international trade of aquatic animals and their products poses a significant risk of transfer between countries. The current status of the Code and Manual is described in detail.

Disinfection in aquaculture.

The authors present information on the susceptibility to various disinfectants of some important pathogens in aquaculture, with special reference to the farming of salmonids. Practical disinfection procedures for use in the aquaculture industry are then described, on the basis of experience obtained in Norway and in other countries with a large salmon-farming industry. In addition to routine disinfection at aquaculture sites, the authors also describe disinfection procedures for use in outbreaks of notifiable diseases, as well as the treatment/disinfection of waste water and offal from the slaughtering and processing of aquaculture products.

Characterization of Vibrio anguillarum and closely related species isolated from farmed fish in Norway.

A total of 264 bacterial strains tentatively or definitely classified as Vibrio anguillarum were examined. The strains were isolated from diseased or healthy Norwegian fish after routine autopsy. With the exception of five isolates from wild saithe (Pollachius virens), the strains originated from nine different species of farmed fish. The bacteria were subjected to morphological, physiological, and biochemical studies, numerical taxonomical analyses, serotyping by slide agglutination and enzyme-linked immunosorbent assay, DNA-plasmid profiling, and in vitro antimicrobial drug susceptibility testing. The results of the microbiological studies were correlated to anamnestic information. The bacterial strains were identified as V. anguillarum serovar O1 (n = 132), serovar O2 (n = 89), serovar O4 (n = 2), serovar O8 (n = 1), and not typeable (n = 1) as well as Vibrio splendidus biovar I (n = 36) and biovar II (n = 1), Vibrio tubiashii (n = 1), and Vibrio fischerii (n = 1). V. anguillarum serovar O1 or O2 was isolated in 176 out of 179 cases of clinical vibriosis in Atlantic salmon (Salmo salar). V. anguillarum serovar O1 was the only serovar isolated from salmonid fish species other than Atlantic salmon, while V. anguillarum serovar O2 was isolated from all marine fish suffering from vibriosis. A 48-Mda plasmid was isolated from all V. anguillarum serovar O1 isolates examined. Serovar O2 isolates did not harbor any plasmids. Resistance against commonly used antibiotic compounds was not demonstrated among V. anguillarum isolates. Neither V. splendidus biovar I nor other V. anguillarum-related species appeared to be of clinical importance among salmonid fish.(ABSTRACT TRUNCATED AT 250 WORDS)

Mercury levels in fish in a river habitat after cessation of mercury contamination.

The rate of decrease shown by mercury levels in brown trout (Salmo trutta) and perch (Perca fluviatilis) collected downstream to a wood pulp factory after a ban on the use of phenyl mercury in the pulp and paper industries was made effective in 1970 has been slow. Even though a river habitat was involved, it seemed to take about 15 years for levels of mercury in downstream fish to fall to those recorded in fish upstream to the wood pulp factory.

Mercury in various tissues of fish caught downstream of a wood pulp factory in the kammerfoss river, South Norway.

The mercury content of perch (Perca fluviatilis) and brown trout (Salmo trutta) from a river in South Norway, previously shown to be contaminated with mercury from a wood pulp factory, was studied during a 5-years period after the use of mercury in the factory had been discontinued in 1970. In addition to muscular tissue, samples of liver, kidney, brain, heart, and gonads were also analyzed in some cases. The mercury level in the musculature remained nearly constant at about 1 mug/g during the years 1971-1975. The organ distribution studies indicate a relatively even concentration level in different organs of moderately exposed individuals, while mercury contents exceeding 100 mug/g have been observed in the liver of fish exposed to high mercury pollution.