Fish Health Management
Dr. Craig Kasper
Aquaculture Disease Processes
FAS 2253
Fish Health Management
• 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.
• Intensive aquaculture – high numbers, close
quarters, lots of food!! (optimal?)
• Enhance 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 fish
• Changes occur over time (type of system)
– Water quality degrades.
– Fish become more crowded.
• Emphasis of Health management:
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Physical features of facility
Use of genetically improved fish
“SPF” stocks
Environmental control
Prophylactic/preventative therapy
Feed quality and quantity
REM: Stress
• Adverse situation that
affects the well-being
of individual animals...
Stress related disease
• Environmental 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 diseases
– Decreased resistance to pathogens
– Endemic pathogens
Location of site
• Soil, water and fish species must be
compatible
• Chose site properly
• Pond aquaculture
• Soil characteristics
• Drainage
Good, bad, or just ugly??
Avoiding exposure
• Best 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?
– What about other countries?
– Do they have regulations?
• Quarantine
– Isolate fish 2 weeks +
• Eradication of Stocks
– Last resort!
– Is it worth it?
– Can you manage around
problem?
Avoiding exposure (cont.)
• Example:
– VHSV (or Egtved) Washington (1989)
• Destroyed adults that were found to have viru
• Destroyed juveniles
– Great lakes (lake trout) Epidermal
epitheliotropic disease (herpesvirus)
• Destroyed fish and disinfected contaminated facilities
• Appears to have worked
– BKD (Wyoming) (1990)
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Destruction of RBT, lake, CTT, and BrT brood stock
Based on highly sensitive detection technique (ELISA)
No evidence for disease
“Was the cost and consequence greater than the value
of what was saved?”
Exposing Dose
• To be sick, fish must be exposed! If no exposure,
liklihood of disease greatly reduced.
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Introduction of disease agent = potential trouble as
we disscussed last time.
• Once pathogen load increases (due to poor
resistance) = DISEASE
• Exposing dosage data usually confined to toxicity
studies.
Extent of contact
• Infection vs Disease?
– Facultative – may live under many conditions
– Obligate – require host to complete life cycle
• Viruses, some bacteria, and few parasites
– Route of transmission
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Oral
External
Vertical
Horizontal
Direct exposure
– Carriers
Protection through segregation
• Young fish/newly hatched fish
– Only innate immunity
– Highly suceptable to stress and water quality
issues
– May need medicated feed.
• Fingerlings
– Immunity increasing
– survive poor water quality for short duration.
• Growout
– Immune system well established.
• Approaching 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!!
• Home aquaria
or large facilities
• Again...Quarantine!
Breeding and Culling
• Important in the development of
domesticated stocks that perform well
• Improve by selecting for desired traits
– disease resistance
– fast growth
– tolerance of stressors
• Future possibilities (genetic
engineering)
– Gene manipulation
– Hybridization/transgenic
REM: EPC
• Eradication: Kill ‘em all!!
• Prevention: Kill what kill’s ‘em!!
• Control: 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
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Plan ahead.
Good health records for each pond.
Good observations.
Good feed.
Water quality/quantity.
Stay on top of things!!
Fish Health Monitoring
• Early 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?