Bergh, Øivind

Korsnes, Kjetil

Mortensen, Stein

English

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Bull. Eur. Ass. Fish Pathol., 26(1) 2006,  1“Eyes wide shut “A critical view of aquaculture healthmanagement and risk factors in the “realworld”S. Mortensen1*, K. Korsnes1, 2 and Ø. Bergh11 Institute of Marine Research, PO Box 1870, Nordnes, NO-5817 Bergen, Norway; 2 Bodø University College, NO-8049 Bodø, Norway.Few aquatic animal diseases have been modelled sufficiently thoroughly to enable a crediblerisk assessment to be carried out – and few aquaculture management models can reliably ensurethat satisfactory health status is maintained in farmed fish or shellfish stocks. However, a centuryof experience has told us a story – of diseases on the move, and about the ways they travel.In spite of all the historical information at ourdisposal, all our knowledge and all ourcommon sense, we still experience that severediseases are spread. We suggest that the riskof spreading diseases cannot be completelyeliminated, but to a great extent we shouldbe able to choose the level of risk we arewilling to accept. We can draw up three roughlevels of risk:Low risk, with no long-distance movementsof aquaculture organisms, or highly restrictedmovements. Autonomous supply of juvenilesin each body of water. High level of controland monitoring.Medium risk. Regional models (based onzoning), with controlled movements. Regularmonitoring of the most fatal diseases.*Corresponding author’s email: stein.mortensen@imr.noBull. Eur. Ass. Fish Pathol., 26(1) 2006, 2High risk. Free movements. Low level ofcontrol and surveillance. Restrictions basedon diagnostics in case of disease outbreaks.Long-distance movements of aquacultureorganisms are still common. Thus, in spite ofa long history of aquatic animal diseases - anda high level of knowledge - European aqua-culture still accepts a relatively high level ofrisk. The mismatch between availableknowledge, the level of precautions taken andthe risk of financial losses due to disease ismainly due to the principle of free trade andthe problem of defining an acceptable levelof restrictions.This may partly be explained by the fact thataquaculture is mainly administrated byeconomists – who often lack knowledge ofdisease ecology, and thus of the dynamics ofdisease dispersion. Moving animals, like anyother goods, may appear to be acceptable inshort-term economic models. There is often aconflict of interest between the short-termfinancial interest of companies, large or small,and the “eternal”, or sustainable perspectiveon aquaculture management that govern-mental agencies should take. We suggest thatthe public debate on aquaculture wouldbenefit by recognising the very existence ofthis conflict of interest.Where the movement of animals for farmingpurposes is concerned, the international andnational regulations in Europe are based inprinciple upon EU Directive 91/67. Anunderstanding of this directive is thusessential for all aquaculture healthmanagement and surveillance. The directiveis based upon some important principles:Fish and shellfish diseases are graded andlisted according to their severity anddistribution. Health management strategydepends on whether or not the diseasesconcerned are notifiable.Movements are only allowed between definedgeographical zones with a similar zoosanitarystatus, or from a disease-free zone to aninfected zone – of course never from aninfected to a disease-free zone.Action is taken if a notifiable disease isdiagnosed. National and internationalveterinary authorities are notified, andmeasures are taken to isolate or eradicate thedisease.The legislation is based upon the estab-lishment of national surveillance programmesthat are intended to ensure that notifiablediseases are not spread, and – if possible -eradicated.The differences between the “paper world”and the “real world” remind us that nature ismore complex than the directive – andencourage us to put a special focus on someproblems related to real risk factors.The system of notifiable diseases is bothimportant and useful. However, the strategyof notifying the diseases relies on the diseasesituation of the past and present, and is notwell adapted to the future situation.Monitoring and disease control based on thisprinciple do not necessarily capture “new” oremerging diseases satisfactorily. Furthermore,the diagnostic work involved is bothexpensive and laborious, with the results thatmonitoring programmes may be limited, inorder to save money. We may also lack basicBull. Eur. Ass. Fish Pathol., 26(1) 2006,  3data from relevant production areas or fromwild populations. The conclusion is thatmapping of animal diseases is never complete,and the diagnostics are always behind thespread of the pathogen.According to the World Organisation forAnimal Health (OIE), a disease is not presentin an area if there are no susceptible species.This seems logical – if we know the life cyclesof the pathogenic agents and are familiar withall the susceptible hosts, latent carriers,dispersal routes, vectors, etc. But we do not!Movement of the primary host is not the onlydispersal route for pathogenic agents.Anything placed in the sea is bound to comeinto contact with the surrounding fauna, anddiseases may spread by the movement ofvectors, latent carriers or contaminated water(e.g. ballast-water). Studies of dispersal routesare important, and we need to acquireinformation about interactions between wildand cultured animals. The principle is thusacceptable only as long as we are successfulin elucidating the numerous aspects of diseaseecology.A positive diagnosis leads to restrictions inor elimination of production, which mayresult in financial loss to farmers. Severaldiseases are therefore underdiagnosed, dueto the fact that we neither know nor want toknow. The conflict of interest between short-term financial interests and sustainabilityadds greatly to this effect. From the point ofview of a government body the long-termpublic interest in surveillance programmesshould be prioritised. It is unacceptable in thelong term to rely solely on disease preventionactions of companies that operate primarilyin the world of short-term interests.The diagnostic question is very important. Ingeneral, diagnostic methods have beendesigned to detect outbreaks of disease, andsampling is usually done followingobservations of clinical signs or pathology. Inthe case of an outbreak, the diagnosticmethods in use do not have to be particularlysensitive, as the pathogen will be present inlarge numbers. A positive diagnosis mayresult in counter-measures such as eradicationof affected stocks and the establishment of azoosanitary zone. However, there are someserious concerns regarding management andcontrol based on the number of outbreaks ofa disease. Movement of latent or asymp-tomatic carriers is probably one of the mostimportant risk factors in the spread of manydiseases - particularly diseases that aretransmitted vertically. The transport of fishwith unknown carrier status for importantpathogens such as infectious salmon anaemiavirus (ISAV) (Nylund et al 2003), nodavirus(Munday et al 2002), and possibly alsoinfectious pancreatic necrosis virus (IPNV)and the alphavirus causing pancreas diseasehas probably contributed to the distributionof these viruses in farmed populations. Here,our lack of knowledge about carrier status,virulence mechanisms and the mechanismsthat trigger outbreaks of disease illustrates thelimitations of traditional diagnosticsurveillance programmes.The medium-risk (“zoning”) model may havetwo dark sides. One is the danger of intro-ducing pathogenic agents if lack ofepizootiological data results in down-classification, resulting in introductions ofdisease-carrying animals. The other is theprinciple of defining an entire national coastBull. Eur. Ass. Fish Pathol., 26(1) 2006, 4as a single zone if it is free from notifiablepathogenic agents. Large zones mean freemovements with in large areas – which offera low level of security if a pathogenic agent isintroduced – or if it is present in carriers thatare being moved over long distances. If anaquaculture species has no known (or notifi-able) pathogens, there will be no zoning at all– meaning free trade (Mortensen 2000).Some potential “hot spots” in the dispersalpattern of aquatic animal diseases tend to beignored or are given low priority – increasingthe risk of rapid dispersal of emergingdiseases. Hatcheries, trade and dispersalcentres for fish and shellfish are epizootiolo-gical “crossroads” which should be underlaidspecial surveillance and control. A relevantexample is bivalve hatcheries. There are onlyabout ten such hatcheries in Europe. A jointmonitoring programme is achievable . . . ifwe wish to.Food and aquaculture animals are subject todifferent legislation (Anon 1991 a & b). Thetransport of live aquaculture organisms mustbe more rigidly controlled than food items,but movements of any live or fresh fish andshellfish may bring the risk of introducingtheir pathogenic agents as well. In this context,relaying of live crustaceans and bivalvesproduces the highest level of risk.Given these examples, disease monitoring andsurveillance systems based on Directive 91/67 are generally speaking not very proactive.From a “third country” point of view,implementing Directive 91/67 might haverepresented a retrograde step from a “lowrisk” to a “high risk” situation. On the otherhand, some improvements have been made:One process is taking place in the industryitself – which has suffered severe losses dueto diseases. Local production networks areemerging, based on quality-controlledproduction chains restricted to geographicallydefined areas. Self-supply of juveniles iscrucial.Collaboration and networking seem to beimproving, linking the industry withmanagement and veterinary services, andensuring a better flow of information. Exper-tise becomes better available throughprofessional networks, (such as the PermanentAdvisory Network for Diseases in Aquacul-ture (PANDA), international collaborativeresearch projects and reference laboratorynetworks.New projects are being generated with the aimof making more use of scientific data in healthmanagement and surveillance, at bothnational and international level. The EU-financed collaboration network projectDIPNET aims at improving our knowledgeon the interaction between wild and farmedfish and shellfish.There is an increasing focus on risk-basedmonitoring. According to the EU’s centralveterinary authority, all farms rearing bivalvemolluscs and fish susceptible to list I and II-diseases will have to be registered by thecompetent authority. Disease preventionmeasures will have to be established, animalhealth monitoring procedures should bebased on a risk assessment and any suspicionof listed diseases must be reported by thecompetent authority to EU.Bull. Eur. Ass. Fish Pathol., 26(1) 2006,  5Quality assurance models are beingimplemented in diagnostic laboratories, andthe reference laboratories are aiming to obtainadequate QA programmes in all networkinglaboratories, through training of personnel,workshops, etc. However it is important toremember that QAis of limited value ifsamples are collected at the wrong locations.The main improvement may be the proposalfor the new “Council Directive on animalhealth requirements for aquaculture animalsand products thereof, and on the preventionand control of certain diseases in aquaticanimals” (Anon, 2005), with which theCommission aims to shift focus to theprevention of disease rather than dealing withit only when an outbreak has occurred.Until the new Directive is implemented, wewho work on various aspects of fish andshellfish diseases all need to ask ourselves thequestion “Why should I care?” . . . We mustexpect all personnel – in all positions – to becompetent, and there is thus no excuse forsaying “We didn’t know” - unless we actuallywish to sit down and wait - take the risk - withour eyes wide shut . . .ReferencesAnonymous (1991 a). Council Directive of 28January 1991 (91/67/EEC), concerning theanimal health conditions governing theplacing on the market of aquaculture animalsand products. Official Journal of the EuropeanCommunities, No. L 46/1.Anonymous (1991 b). Council Directive of 15July 1991 (91/492/EEC), laying down thehealth conditions for the production and theplacing on the market of live bivalve molluscs.Official Journal of the European Commu-nities, No. L 288/1.Anonymous (2005). Proposal for a newCouncil Directive on animal healthrequirements for aquaculture animals andproducts thereof, and on the prevention andcontrol of certain diseases in aquatic animals.Commision of the European Communities,Brussels, august 2005.Mortensen SH (2000). Introductions andtransfers of scallops, from an animal healthpoint of view. Aquaculture International 8, 123-138.Munday BL, Kwang J & Moody N (2002).Betanodavirus infections of teleost fish: areview. Journal of Fish Diseases 25, 127-142.Nylund A, Devold M, Plarre H, Isdal E &Aarseth M (2003). Emergence and main-tenance of infectious salmon anaemia virus(ISAV) in Europe: a new hypothesis. Diseasesof Aquatic Organisms 56, 11-24.

"Eyes wide shut" - A critical view of aquaculture health management and risk factors in the "real world"

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"Eyes wide shut" - A critical view of aquaculture health management and risk factors in the "real world"

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