Fish Health ManagementFish Health Management

Dr. Craig KasperDr. Craig Kasper

Aquaculture Disease ProcessesAquaculture Disease Processes

FAS 2253FAS 2253

Fish Health ManagementFish Health Management

• GOALS :GOALS :– Prevent introduction of disease to healthy animals. Prevent introduction of disease to healthy animals.

– Prevent propigation of existing disease agents.Prevent propigation of existing disease agents.

– Production of healthy, high quality fish.Production of healthy, high quality fish.

Principles of Health MaintenancePrinciples of Health Maintenance

• Maintain conditions which are designed to Maintain conditions which are designed to optimize growth, feed conversion, optimize growth, feed conversion, reproduction and survival.reproduction and survival.

• Intensive aquaculture – high numbers, close Intensive aquaculture – high numbers, close quarters, lots of food!! (optimal?)quarters, lots of food!! (optimal?)

• Enhance natural resistance Enhance natural resistance – Well managed fish have healthy immune systems! Well managed fish have healthy immune systems! – Healthy fish give rise to healthier offspring!Healthy fish give rise to healthier offspring!

Maintaining HealthMaintaining Health• Inverse relationship between Inverse relationship between

environmental quality and disease status environmental quality and disease status of fishof fish

• Changes occur over time (type of system)Changes occur over time (type of system)– Water quality degrades.Water quality degrades.– Fish become more crowded.Fish become more crowded.

• Emphasis of Health management:Emphasis of Health management:– Physical features of facilityPhysical features of facility– Use of genetically improved fishUse of genetically improved fish– ““SPF” stocksSPF” stocks– Environmental control Environmental control – Prophylactic/preventative therapyProphylactic/preventative therapy– Feed quality and quantityFeed quality and quantity

REM: StressREM: Stress

• Adverse situation thatAdverse situation that

affects the well-beingaffects the well-being

of individual animals...of individual animals...

Stress related diseaseStress related disease

• Environmental associatedEnvironmental associated– Wild fish are in equilibrium with there Wild fish are in equilibrium with there

pathogens.pathogens.– Captive fish are much more effected by Captive fish are much more effected by

changes in temp. or water quality due to changes in temp. or water quality due to excessive crowding, handling, etc.excessive crowding, handling, etc.

• Microbial diseasesMicrobial diseases– Decreased resistance to pathogensDecreased resistance to pathogens– Endemic pathogensEndemic pathogens

Location of siteLocation of site

• Soil, water and fish species must be Soil, water and fish species must be compatible compatible

• Chose site properlyChose site properly• Pond aquaculturePond aquaculture

• Soil characteristicsSoil characteristics

• DrainageDrainage

Good, bad, or just ugly??

Avoiding exposureAvoiding exposure

• Best method to control infectious Best method to control infectious diseasedisease– Water is effective at delivering pathogens Water is effective at delivering pathogens

to fish (endemic)to fish (endemic)

– Don’t feed contaminated feed.Don’t feed contaminated feed.

Avoiding exposureAvoiding exposure• REM: U.S.: Title 50?REM: U.S.: Title 50?

– What about other countries? What about other countries? – Do they have regulations?Do they have regulations?

• QuarantineQuarantine– Isolate fish 2 weeks +Isolate fish 2 weeks +

• Eradication of StocksEradication of Stocks– Last resort!Last resort!– Is it worth it?Is it worth it?– Can you manage aroundCan you manage around problem? problem?

Avoiding exposure (cont.)Avoiding exposure (cont.)

• Example: Example: – VHSV (or Egtved) Washington (1989)VHSV (or Egtved) Washington (1989)

• Destroyed adults that were found to have viruDestroyed adults that were found to have viru• Destroyed juvenilesDestroyed juveniles

– Great lakes (lake trout) Epidermal Great lakes (lake trout) Epidermal epitheliotropic disease (herpesvirus)epitheliotropic disease (herpesvirus)

• Destroyed fish and disinfected contaminated facilitiesDestroyed fish and disinfected contaminated facilities• Appears to have workedAppears to have worked

– BKD (Wyoming) (1990)BKD (Wyoming) (1990)• Destruction of RBT, lake, CTT, and BrT brood stock Destruction of RBT, lake, CTT, and BrT brood stock • Based on highly sensitive detection technique (ELISA)Based on highly sensitive detection technique (ELISA)• No evidence for diseaseNo evidence for disease• ““Was the cost and consequence greater than the value Was the cost and consequence greater than the value

of what was saved?”of what was saved?”

Exposing DoseExposing Dose

• To be sick, fish must be exposed! If no exposure, To be sick, fish must be exposed! If no exposure, liklihood of disease greatly reduced.liklihood of disease greatly reduced.

• Introduction of disease agent = potential trouble as Introduction of disease agent = potential trouble as we disscussed last time.we disscussed last time.

• Once pathogen load increases (due to poor Once pathogen load increases (due to poor resistance) = DISEASEresistance) = DISEASE

• Exposing dosage data usually confined to toxicity Exposing dosage data usually confined to toxicity studies.studies.

Extent of contactExtent of contact• Infection vs Disease?Infection vs Disease?

– FacultativeFacultative – may live under many conditions – may live under many conditions– ObligateObligate – require host to complete life cycle – require host to complete life cycle

• Viruses, some bacteria, and few parasitesViruses, some bacteria, and few parasites

– Route of transmissionRoute of transmission • OralOral• ExternalExternal• Vertical Vertical • HorizontalHorizontal• Direct exposureDirect exposure

– CarriersCarriers

Protection through segregationProtection through segregation

• Young fish/newly hatched fishYoung fish/newly hatched fish– Only innate immunityOnly innate immunity– Highly suceptable to stress and water quality Highly suceptable to stress and water quality issuesissues– May need medicated feed.May need medicated feed.

• FingerlingsFingerlings– Immunity increasing Immunity increasing – survive poor water quality for short duration.survive poor water quality for short duration.

• GrowoutGrowout– Immune system well established.Immune system well established.

• Approaching market/release sizeApproaching market/release size– Very resistant to diseaseVery resistant to disease– Can survive in poorest water qualityCan survive in poorest water quality

Addition of new fishAddition of new fish

• Should take needed precautions when Should take needed precautions when adding new fish to existing adding new fish to existing stocks...duh!!stocks...duh!!

• Home aquaria Home aquaria

or large facilitiesor large facilities

• Again...Quarantine!Again...Quarantine!

Breeding and CullingBreeding and Culling

• Important in the development of Important in the development of domesticated stocks that perform welldomesticated stocks that perform well

• Improve by selecting for desired traitsImprove by selecting for desired traits– disease resistancedisease resistance– fast growthfast growth– tolerance of stressorstolerance of stressors

• Future possibilities (genetic engineering)Future possibilities (genetic engineering)– Gene manipulationGene manipulation– Hybridization/transgenicHybridization/transgenic

REM: EPCREM: EPC

• Eradication: Kill ‘em all!!Eradication: Kill ‘em all!!

• Prevention: Kill what kill’s ‘em!!Prevention: Kill what kill’s ‘em!!

• Control: Control: Reduction of problem to an Reduction of problem to an economically/biologically manageable leveleconomically/biologically manageable level– Do all you can.Do all you can.– Be prepared for the worst.Be prepared for the worst.– Sometimes fish just get sick!! Sometimes fish just get sick!!

Anticipating problemsAnticipating problems

• Plan ahead.Plan ahead.

• Good health records for each pond.Good health records for each pond.

• Good observations.Good observations.

• Good feed.Good feed.

• Water quality/quantity.Water quality/quantity.

• Stay on top of things!! Stay on top of things!!

Fish Health MonitoringFish Health Monitoring

• Early diagnosisEarly diagnosis– Know what “normal” is!Know what “normal” is! – Know what treatments are available. (and Know what treatments are available. (and

how to utilize them.)how to utilize them.)

– Know what Know what abnormalabnormal is. is.

– Remain proactive.Remain proactive.

Question?Question?You are in charge of fish health monitoring at an You are in charge of fish health monitoring at an

aquaculture facility. aquaculture facility.

During morning rounds you notice that a first use During morning rounds you notice that a first use pond containing RBT (50g/fish) is having some pond containing RBT (50g/fish) is having some problems. Fish appear lethargic, and some dark problems. Fish appear lethargic, and some dark fish are observed.fish are observed.

1.1. What possible problems may be causing this?What possible problems may be causing this?

2.2. How would you narrow the possibilities down?How would you narrow the possibilities down?

3.3. You suspect the problem to be disease related, You suspect the problem to be disease related, what would you do?what would you do?