Fish Health Management Dr. Craig Kasper Aquaculture Disease Processes FAS 2253

Fish Health Management GOALS :GOALS : –Prevent introduction of disease to healthy animals. –Prevent propigation of existing disease agents. –Production of healthy, high quality fish.

Principles of Health Maintenance Maintain conditions which are designed to optimize growth, feed conversion, reproduction and survival.Maintain conditions which are designed to optimize growth, feed conversion, reproduction and survival. Intensive aquaculture – high numbers, close quarters, lots of food!! (optimal?)Intensive aquaculture – high numbers, close quarters, lots of food!! (optimal?) Enhance natural resistanceEnhance natural resistance –Well managed fish have healthy immune systems! –Healthy fish give rise to healthier offspring!

Maintaining Health Inverse relationship between environmental quality and disease status of fishInverse relationship between environmental quality and disease status of fish Changes occur over time (type of system)Changes occur over time (type of system) – Water quality degrades. – Fish become more crowded. Emphasis of Health management:Emphasis of Health management: –Physical features of facility –Use of genetically improved fish –“SPF” stocks –Environmental control –Prophylactic/preventative therapy –Feed quality and quantity

REM: Stress Adverse situation thatAdverse situation that affects the well-being affects the well-being of individual animals... of individual animals...

Stress related disease Environmental associatedEnvironmental associated – Wild fish are in equilibrium with there pathogens. – Captive fish are much more effected by changes in temp. or water quality due to excessive crowding, handling, etc. Microbial diseasesMicrobial diseases –Decreased resistance to pathogens –Endemic pathogens

Location of site Soil, water and fish species must be compatibleSoil, water and fish species must be compatible Chose site properlyChose site properly Pond aquaculturePond aquaculture Soil characteristicsSoil characteristics DrainageDrainage Good, bad, or just ugly??

Avoiding exposure Best method to control infectious diseaseBest method to control infectious disease –Water is effective at delivering pathogens to fish (endemic) – Don’t feed contaminated feed.

Avoiding exposure REM: U.S.: Title 50?REM: U.S.: Title 50? –What about other countries? –Do they have regulations? QuarantineQuarantine –Isolate fish 2 weeks + Eradication of StocksEradication of Stocks –Last resort! –Is it worth it? –Can you manage around problem? problem?

Avoiding exposure (cont.) Example:Example: –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 epitheliotropic disease (herpesvirus) Destroyed fish and disinfected contaminated facilitiesDestroyed fish and disinfected contaminated facilities Appears to have workedAppears to have worked –BKD (Wyoming) (1990) Destruction of RBT, lake, CTT, and BrT brood stockDestruction 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 of what was saved?”“Was the cost and consequence greater than the value of what was saved?”

Exposing Dose Exposing Dose To be sick, fish must be exposed! If no exposure, liklihood of disease greatly reduced.To be sick, fish must be exposed! If no exposure, liklihood of disease greatly reduced. Introduction of disease agent = potential trouble as we disscussed last time. Introduction of disease agent = potential trouble as we disscussed last time. Once pathogen load increases (due to poor resistance) = DISEASEOnce pathogen load increases (due to poor resistance) = DISEASE Exposing dosage data usually confined to toxicity studies.Exposing dosage data usually confined to toxicity studies.

Extent of contact Extent of contact Infection vs Disease?Infection vs Disease? –Facultative – may live under many conditions –Obligate – require host to complete life cycle Viruses, some bacteria, and few parasitesViruses, some bacteria, and few parasites –Route of transmission Oral Oral External External Vertical Vertical Horizontal Horizontal Direct exposure Direct exposure –Carriers

Protection through segregation Protection through segregation Young fish/newly hatched fishYoung fish/newly hatched fish – Only innate immunity – Highly suceptable to stress and water quality issues issues – May need medicated feed. FingerlingsFingerlings –Immunity increasing – survive poor water quality for short duration. GrowoutGrowout – Immune system well established. Approaching market/release sizeApproaching market/release size –Very resistant to disease –Can survive in poorest water quality

Addition of new fish Should take needed precautions when adding new fish to existing stocks...duh!!Should take needed precautions when adding new fish to existing stocks...duh!! Home aquariaHome aquaria or large facilities or large facilities Again...Quarantine!Again...Quarantine!

Breeding and Culling Important in the development of domesticated stocks that perform wellImportant in the development of domesticated stocks that perform well Improve by selecting for desired traitsImprove by selecting for desired traits – disease resistance – fast growth – tolerance of stressors Future possibilities (genetic engineering)Future possibilities (genetic engineering) –Gene manipulation –Hybridization/transgenic

REM: EPC Eradication: Kill ‘em all!!Eradication: Kill ‘em all!! Prevention: Kill what kill’s ‘em!!Prevention: Kill what kill’s ‘em!! Control: Reduction of problem to an economically/biologically manageable levelControl: Reduction of problem to an economically/biologically manageable level – Do all you can. – Be prepared for the worst. – Sometimes fish just get sick!!

Anticipating 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 Monitoring Early diagnosisEarly diagnosis –Know what “normal” is! – Know what treatments are available. (and how to utilize them.) – Know what abnormal is. – Remain proactive.

Question? You are in charge of fish health monitoring at an aquaculture facility. During morning rounds you notice that a first use pond containing RBT (50g/fish) is having some problems. Fish appear lethargic, and some dark fish are observed. 1.What possible problems may be causing this? 2.How would you narrow the possibilities down? 3.You suspect the problem to be disease related, what would you do?