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Fish Diseases Lesson 2

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Some strains of known fish pathogens may not always cause disease ... Enteric Septicemia (ESC) - 23-27 C (73-81) Aeromonas 25-30 C (77-86) ... – PowerPoint PPT presentation

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Title: Fish Diseases Lesson 2


1
Fish DiseasesLesson 2
  • Factors Involved in the Outbreak of Disease

2
Factors Involved in the Outbreak of Disease
  • A susceptible host
  • A virulent pathogen
  • Proper environmental conditions

3
1. A susceptible host
  • Good diet and clean water supply
  • Avoid introducing fish from another hatchery -
    Quarantine
  • Hosts defense system

4
Fishes Lines of Defense
  • Mechanical - Skin, Scales and Mucus
  • Physiological -
  • White blood cells (Phagocytosis)
  • Liver detoxifies chemicals from water
  • Local Tissue reactions
  • Immune system
  • Active against bacteria, parasites viruses

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2. Virulent Pathogen
  • Not all bacteria cause disease
  • Some strains of known fish pathogens may not
    always cause disease
  • Bacteria can become more virulent by being
    passed through a fish

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3. Adverse Environment
  • Changes in environment
  • Certain temps favor or hinder pathogen
  • Facility design - tanks vs ponds
  • Biological factors
  • Hatcheries with well water vs surface water

11
Critical Levels of Water Quality
  • Oxygen
  • Nitrites
  • Ammonia
  • Total Alkalinity
  • Total Hardness
  • pH
  • Temperature

12
Critical Temperatures
  • Optimum varies with species
  • Tilapia - above 21 C (70 F)
  • Trout - 10-16 C (50-61 F)
  • Catfish 10-30 C Optimum 25-30 C (77-86)

13
Critical Temps for Pathogens
  • Ichthyopthirius Multifilis (Ich)
  • Most severe 20-22 C ( 68-72 F)
  • Can occur down to 5 C
  • Seldom above 23 C ( 73)
  • Channel Catfish Virus (CCV)
  • occurs above 23 C
  • Enteric Septicemia (ESC) -
  • 23-27 C (73-81)
  • Aeromonas 25-30 C (77-86)

14
Factors in Disease Development
  • 1. Source of infection
  • 2. Mode (method) of infection
  • 3. Portal of entry
  • 4. Virulence of the organism
  • 5. Resistance of the host

Break the Chain
15
Source of Infection
  • Infected fish, dead fish , sick fish, carriers
  • Infected fish eggs from carrier broodstock
  • Contaminated water supply
  • Contaminated Feed
  • Man and his activities

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Mode of Transmission
  • Through the water
  • water with all the waste products from the fish
    make ideal conditions for pathogens to survive

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Portal of Entry
  • Gills - parasites can pierce gills and bacteria
    can enter
  • Skin - breaks in skin and mucus by parasites or
    handling
  • Ingestion-Dont feed wild, uncooked fish

Break the Chain
18
Virulence of Pathogen
  • Varies by species of virus or bacteria
  • Different strains
  • Pass-through effect

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Resistance of Host
  • Different than immunity
  • Immunity is acquired by previous exposure to the
    infection
  • Natural Resistance
  • substances in the fish
  • Non-specific

20
Factors Effecting Natural Resistance
  • White Blood cells
  • Tissue integrity
  • Nutrition
  • Age of Animal
  • Strain of species
  • Temperature

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Resistance
  • Does not mean that the animal cannot be infected,
    but that the host has the ability to subdue the
    pathogen to the point where it will not cause
    disease.

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