Fish Health Management

1
Fish Health Management

• Dr. Craig Kasper
• Aquaculture Disease Processes
• FAS 2253

2
Fish Health Management

• GOALS
• Prevent introduction of disease to healthy
  animals.
• Prevent propigation of existing disease agents.
• Production of healthy, high quality fish.

3
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!

4
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
• Physical features of facility
• Use of genetically improved fish
• SPF stocks
• Environmental control
• Prophylactic/preventative therapy
• Feed quality and quantity

5
REM Stress

• Adverse situation that
• affects the well-being
• of individual animals...

6
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

7
Location of site

• Soil, water and fish species must be compatible
• Chose site properly
• Pond aquaculture
• Soil characteristics
• Drainage

Good, bad, or just ugly??
8
Avoiding exposure

• Best method to control infectious disease
• Water is effective at delivering pathogens to
  fish (endemic)
• Dont feed contaminated feed.

9
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?

10
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)
• 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?

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Exposing Dose

• 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.
• Once pathogen load increases (due to poor
  resistance) DISEASE
• Exposing dosage data usually confined to toxicity
  studies.

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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
• Oral
• External
• Vertical
• Horizontal
• Direct exposure
• Carriers

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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

14
Addition of new fish

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

15
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

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REM EPC

• Eradication Kill em all!!
• Prevention Kill what kills 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!!

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Anticipating problems

• Plan ahead.
• Good health records for each pond.
• Good observations.
• Good feed.
• Water quality/quantity.
• Stay on top of things!!

18
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.

19
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.
• What possible problems may be causing this?
• How would you narrow the possibilities down?
• You suspect the problem to be disease related,
  what would you do?