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Fish Health and Disease
Part 1: Epidemiology and Immunity
Definitions
 Epidemiology
 The study of the transmission and control of disease
 Immunology
 The study of the components of the immune system,
immunity from disease and the immune response
Epidemiology- disease within pop’s
Major factors affecting disease
 Exposure (time)
 Specificity/species fidelity
 Virulence/deadliness
 Ability to use a vector or
 Pathogenicity/how
reservoir
 Host behavioral shifts
 Host response
type/immune
contagious it is
 Incubation period
Disease = Opportunity & Condition
 All 3 are required for disease to proliferate
How to spread disease
 Transmission types
 Direct – through contact: high density situations
 Person to person
 animal to person - zoonoses
 mother to child – vertical transmission
 Indirect – without contact: density independent
 Retention on objects/food
 droplets & particles in air
 bites and stings
Kissing bug Triatoma sp.
Immune System
 Purpose: Recognize and destroy non-self cells/particles
 Non-self particles = antigens
 Innate immune system
 Immediate, non-specific response
±’s ?
 No immunological memory/you don’t retain antibody memory
 Adaptive immune system
±’s ?
 Time lag between exposure and response, specific response
 Exposure leads to immunological memory
Immune Response
 Cell-mediated response
 Macrophages
 Natural killer cells /mast cells
 Antigen-specific cytotoxic T-lymphocytes
 and Various cytokines in response to an antigen
 Humoral response
 Activated antibodies stemming from B lymphocytes
 Employs specific cytokines
 Produces/utilizes memory cells
 and Stimulates effector functions of antibodies
Vaccination
 Induces adaptive immune system through cell-mediated and
humoral responses
 Produces memory cells to combat future exposures
 Types of vaccines
 Dead viral particles are administered – boosters required
 Low virulence/live viral particles – few to no boosters
 Subunit vaccination – non-viral protein administered alone or
within a non-harmful virus – sometimes ineffective
Red Queen Hypothesis
 "It takes all the running you can do, to keep in the same
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place.”
Constant adaptation among hosts and pathogens
“Building better bugs”
Problems with antibiotics
Problems with vaccine development
Hygiene hypothesis: Exposure to natural
low-level pathogens increases overall immunity
 Ways we have circumvented natural immunity
 Sterilization
 Vaccination
 Amplification
 Problems with immunity recently developed in humans
 Immunodeficiencies – inactivity of parts of the immune system
 Auto-immune diseases – immune system attacks itself
 Hypersensitivity – over-expression of immune response
SUMMARY
 To avoid disease you must have limited exposure
 both time and density dependant
 The type of response depends on previous exposure
 Innate or adaptive response
 Cell-mediated and humoral responses in both types
 Vaccines have + and – attributes
 Specific response
 Red Queen hypothesis
 Exposure to naturally-occurring antigens can boost immune
system
 Hygiene hypothesis
Fish Health and Disease
Part 2: Diseases in Aquaculture
Pathogens in Nature
 Not such a bad thing
 Typically infections are not virulent when prevalent
 Aid in feeding upper trophic levels
 Remove susceptible individuals from population
 Survival of fittest
 Link multiple trophic levels within an ecosystem
 Useful eco-indicators of ecosystem stressors
 When epidemics occur
 Could be a sign of host population structure
 Have the potential to substantially decrease host populations
Pathogens in Aquaculture
 Not necessarily a health risk
 COOK IT & COOK IT WELL!
 More likely to economically impact industry by changing
 Texture
 Appearance
 Taste
 Perception of product is everything = $$
 Value added products
 Top dollar for the most attractive product
 Single oysters vs. clusters
 Proper pigments in fish filets
Disease Concerns in Aquaculture
 Major concerns for disease epidemics in
Extensive
Semi-intensive
Intensive
 Why?
 Crowding
 Introduced pathogens
 Competition
 Introduced hosts
 Food
 Spread to native pop’s
 Space
 Competition with native pop’s
 Mates
 Water conditions
Requirements for Disease
 All 3 must be present for an outbreak
System Design and Pathogen Transmission
Net pen/cage
Semi-closed/
Recirculating
+
+
+
-
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Disease
transmission
Permeability
of containment
Interactions
with native sp.
Wastewater
treatment
Examples of Diseases in Aquaculture
 Salmonid farming
 Catfish farming
 Tilapia
 Shrimp Farming
 Abalone
 Oysters
ambhanoi.um.dk
Usfws.gov
Salmonids
 Bacterial disease
Salmonids it infects
Non-salmonid
species it infects
 Furcunculosis-Aeromonas salmonicida
Atlantic codsalmon
Gadus morhuaSalmo salar
Atlantic
Sea bream Sparus aurata
Amago
salmon
Oncorhynchus rhodurus
Turbot Psetta maxima /Scophthalmus maximus
Brook
Salvelinus fontinalis
Americantrout
eel Anguilla rostrata
Brassy
hankinsoni
Brownminnow
trout Hybognathus
Salmo
trutta m. lacustris
Brook
stickleback
inconstans Carp tshawytscha
Cyprinus carpio
Chinook
salmonCulaeaOncorhynchus
Catfish Silurus glanis
Chum
Oncorhynchus
Chestnutsalmon
lamprey Ichthyomyzon
castaneum keta
Coho
salmon
kisutch
Common
shiner NotropisOncorhynchus
cornutus
Creek
chub Semotilus
Cutthroat
trout atromaculatus
Salmo clarki
European eel Anguilla anguilla
Dolly
Varden
Salvelinus malma
Fathead minnow Pimephales promelas
Japanese
Salvelinus leucomaenis
Goby Cottuschar
gobio
Goldentrout
shiner Notemigonus
crysoleucasnamaycush
Lake
Salvelinus
Groper
Roccus mississippiensis
Masu salmon
Oncorhynchus masou
Lamprey Not specified
Pink
salmon
Minnow
Phoxinus phoxinusOncorhynchus gorbuscha
Pollan
Coregonus pollan
Mottled sculpin Cottus bairdi
Northern
Esox luciusOncorhynchus mykiss
Rainbowpike
trout
Paddlefish Polyodon spathula
Sea
trout
Salmo trutta m. trutta
Redbelly dace Chromomus eos
Sockeye
Oncorhynchus
Smallmouthsalmon
bass Micropterus
dolomieui nerka
Stickleback Gasterosteus aculeatus
American Fisheries Society
T Håstein disease-watch.com
Salmonids
Bacterial Infections
 Bacterial Kidney Disease – Renibacterium salmoninarum
Redmouth disease
 Enteric septicaemia – Edwardsiella sp.
 Enteric Redmouth Disease (ERM) – Yersinia ruckeri
 Pseudotuberculosis – Photobacterium damsela subsp. piscicida
 Salmon Rickettsial Disease – Piscirickettsia salmonis
 Vibrosis –Vibrio anguillarum
 Hitra disease – Vibrio salmonicida
ulcer from
Vibrio
Bacterial Dermal
kidney disease
(BKD)
RickettsiaPhotobacterium family infecting gills
Salmonids
Viral infections
 Infectious haematopoietic necrosis (IHN)
 Infectious pancreatic necrosis virus
Salmonids
Parasites
 Skin & gill fluke Gyrodactylus salaris
 flatworm
 Whirling disease Myxobolus cerebralis
 protozoan
Skull deformation from Myxobolus cerebralis
Atlantic salmon with Gyrodactylosis
Darkening of skin from anus to tail
Salmonids
Ecto-parasites
 Sea lice
Catfish Aquaculture
 Bacterial infections in catfish
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Aeromonas hydrophila
Edwardsiella ictaluri
Aeromonashydrophila
Edwardsiella tarda
Flexibacter columnaris
Ich infection on a catfish
 Channel catfish virus
 Winter kill syndrome – fungal infection
 Saprolegnia sp.
 Parasites
CCV
 White spot disease/protozoan - Icthyophthirius multifiliis = ich!
 Trichodina, Glossatella, Scyphidia and Epistylis and monogeneans
 Fish louce, Ergasilus sp., Argulus sp., Lernaea cyprinacae
 “Brown blood disease”: elevated NO2 in water – not a pathogen
 “Broken-skull disease”: lack of ascorbic acid – not a pathogen
Tilapia
 Bacterial disease
 Streptococcosis
Legions on bulging eyes
Shrimp farming
 Bacterial infections
 Vibrio sp.
 Viral infections
White spot virus syndrome
 White spot syndrome – Whispovirus
 Yellow head syndrome
 Protozoan parasites
 Milk shrimp syndrome – Agmasoma duorara
Cotton/milk shrimp syndrome
Abalone
 Abalone Virus Ganglioneuritis (AVG)
 Herpes-like virus that originated from farmed cultures
Oysters
 Parasitic protozoans
 MSX – Haplosporidium nelsoni
 Dermo – Perkinsus marinus
 Gastropod predators and parasites
 Boonea sp.
 Urosalpinx sp.
Prevention, Prevention, Prevention!
 The ultimate way to stop an outbreak is to prevent it
 Prevent stressful situations
 Proper stocking situations
 Proper management practices
 Ideal water treatment
Prevention measures
 Vaccinations
 Stress-treatments (chemical)
 Anti-biotics
 Selective breeding (unintentional & intentional)
 Disease-free brood stocks
 Batch culture/ single batches reared to size
 Fungal control of eggs
 Intensive systems
 Control of multiple environmental factors
SUMMARY
 Multiple pathogens afflict nearly all farmed species
 Preventative technologies are constantly being developed
 Good management and farming practices aid in success
 Parasites and pathogens are normal parts of natural
ecosystems
 Eradication = species extinction
= lack of natural community complexity
 For the purposes of human sustenance
 Limit disease in non-natural stocks
 Biosecurity