Part 1: Epidemiology and Immunity Fish Health and Disease.

Part 1: Epidemiology and Immunity

Fish Health and Disease

DefinitionsEpidemiology

The study of the transmission and control of disease

ImmunologyThe study of the components of the

immune system, immunity from disease and the immune response 

Epidemiology- disease within

pop’s

Major factors affecting disease

Disease = Opportunity & Condition

All 3 are required for disease to proliferate

How to spread diseaseTransmission types

Direct – through contact: high density situations Person to person animal to person - zoonoses mother to child – vertical transmission

Indirect – without contact: density independentRetention on objects/food droplets & particles in air bites and stings

Kissing bug Triatoma sp.

Immune SystemPurpose: Recognize and destroy non-self

cells/particlesNon-self particles = antigens

Innate immune systemImmediate, non-specific responseNo immunological memory/you don’t retain antibody

memory

Adaptive immune systemTime lag between exposure and response, specific

responseExposure leads to immunological memory

±’s ?

±’s ?

Immune ResponseCell-mediated response

Macrophages Natural killer cells /mast cellsAntigen-specific cytotoxic T-lymphocytesand Various cytokines in response to an

antigenHumoral response

Activated antibodies stemming from B lymphocytes

Employs specific cytokines Produces/utilizes memory cellsand Stimulates effector functions of

antibodies

VaccinationInduces adaptive immune system through cell-

mediated and humoral responses Produces memory cells to combat future

exposures

Types of vaccinesDead viral particles are administered – boosters

requiredLow virulence/live viral particles – few to no boostersSubunit 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 place.”Constant adaptation among hosts and

pathogens“Building better bugs”Problems with antibioticsProblems with vaccine development

Hygiene hypothesis: Exposure to natural low-level pathogens increases overall immunity

Ways we have circumvented natural immunitySterilizationVaccinationAmplification

Problems with immunity recently developed in humansImmunodeficiencies – inactivity of parts of the immune

systemAuto-immune diseases – immune system attacks itselfHypersensitivity – over-expression of immune response

SUMMARYTo avoid disease you must have limited exposure

both time and density dependantThe type of response depends on previous

exposureInnate or adaptive responseCell-mediated and humoral responses in both types

Vaccines have + and – attributes Specific responseRed Queen hypothesis

Exposure to naturally-occurring antigens can boost immune systemHygiene hypothesis

Part 2: Diseases in Aquaculture

Fish Health and Disease

Pathogens in NatureNot 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 ecosystemUseful eco-indicators of ecosystem stressors

When epidemics occurCould be a sign of host population structureHave the potential to substantially decrease

host populations

Pathogens in AquacultureNot necessarily a health risk

COOK IT & COOK IT WELL!More likely to economically impact industry by

changingTextureAppearanceTaste

Perception of product is everything = $$Value added products

Top dollar for the most attractive productSingle oysters vs. clustersProper pigments in fish filets

Disease Concerns in Aquaculture

Major concerns for disease epidemics in Extensive Semi-intensive

Intensive

Requirements for Disease

All 3 must be present for an outbreak

System Design and Pathogen Transmission

Net pen/cage

Semi-closed/Recirculating

Disease transmission

Wastewatertreatment

Permeabilityof containment

Interactionswith native sp.

+ + +

+

-

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Examples of Diseases in Aquaculture

Salmonid farmingCatfish farmingTilapiaShrimp FarmingAbaloneOysters

ambhanoi.um.dkUsfws.gov

SalmonidsBacterial diseaseFurcunculosis-Aeromonas salmonicida

Salmonids it infectsAtlantic salmon   Salmo salar Amago salmon   Oncorhynchus rhodurus Brook trout   Salvelinus fontinalis Brown trout   Salmo trutta m. lacustris Chinook salmon   Oncorhynchus tshawytscha Chum salmon   Oncorhynchus keta Coho salmon   Oncorhynchus kisutch Cutthroat trout   Salmo clarki Dolly Varden   Salvelinus malma Japanese char   Salvelinus leucomaenis Lake trout   Salvelinus namaycush Masu salmon   Oncorhynchus masou Pink salmon   Oncorhynchus gorbuscha Pollan   Coregonus pollan Rainbow trout   Oncorhynchus mykiss Sea trout   Salmo trutta m. trutta Sockeye salmon   Oncorhynchus nerka

American Fisheries Society

T Håstein disease-watch.com

Non-salmonid species it infectsAtlantic cod   Gadus morhua Sea bream   Sparus aurata Turbot   Psetta maxima /Scophthalmus maximusAmerican eel   Anguilla rostrata Brassy minnow   Hybognathus hankinsoni Brook stickleback   Culaea inconstans Carp   Cyprinus carpio Catfish   Silurus glanis Chestnut lamprey   Ichthyomyzon castaneum Common shiner   Notropis cornutus Creek chub   Semotilus atromaculatus European eel   Anguilla anguilla Fathead minnow   Pimephales promelas Goby   Cottus gobio Golden shiner   Notemigonus crysoleucas Groper   Roccus mississippiensis Lamprey   Not specified Minnow   Phoxinus phoxinus Mottled sculpin   Cottus bairdi Northern pike   Esox lucius Paddlefish   Polyodon spathula Redbelly dace   Chromomus eos Smallmouth bass   Micropterus dolomieui Stickleback   Gasterosteus aculeatus

Bacterial InfectionsBacterial Kidney Disease – Renibacterium

salmoninarum Enteric septicaemia – Edwardsiella sp.Enteric Redmouth Disease (ERM) – Yersinia

ruckeriPseudotuberculosis – Photobacterium

damsela subsp. piscicida Salmon Rickettsial Disease – Piscirickettsia

salmonis Vibrosis – Vibrio anguillarumHitra disease – Vibrio salmonicida

Salmonids

Rickettsia

Redmouth disease

Bacterial kidney disease (BKD) Photobacterium family infecting gillsDermal ulcer from Vibrio

Viral infections

Infectious haematopoietic necrosis (IHN)Infectious pancreatic necrosis virus

Salmonids

Parasites

Skin & gill fluke Gyrodactylus salarisflatworm

Whirling disease Myxobolus cerebralisprotozoan

Atlantic salmon with Gyrodactylosis

Skull deformation from Myxobolus cerebralis

Salmonids

Darkening of skin from anus to tail

Ecto-parasites

Sea lice

Salmonids

Catfish Aquaculture

Bacterial infections in catfishAeromonas hydrophila Edwardsiella ictaluriAeromonashydrophilaEdwardsiella tardaFlexibacter columnaris

Channel catfish virusWinter kill syndrome – fungal infection

Saprolegnia sp.Parasites

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

CCV

Ich infection on a catfish

Tilapia

Bacterial diseaseStreptococcosis

Legions on bulging eyes

Shrimp farming

Bacterial infectionsVibrio sp.

Viral infectionsWhite spot syndrome – WhispovirusYellow head syndrome

Protozoan parasitesMilk shrimp syndrome – Agmasoma duorara

White spot virus syndrome

Cotton/milk shrimp syndrome

AbaloneAbalone Virus Ganglioneuritis (AVG)

Herpes-like virus that originated from farmed cultures

Oysters

Parasitic protozoansMSX – Haplosporidium nelsoni Dermo – Perkinsus marinus

Gastropod predators and parasitesBoonea sp.Urosalpinx sp.

Prevention, Prevention, Prevention!

The ultimate way to stop an outbreak is to prevent it

Prevent stressful situationsProper stocking situationsProper management practicesIdeal water treatment

Prevention measuresVaccinationsStress-treatments (chemical)Anti-bioticsSelective breeding (unintentional &

intentional)Disease-free brood stocksBatch culture/ single batches reared to sizeFungal control of eggs

Intensive systemsControl of multiple environmental factors

SUMMARYMultiple pathogens afflict nearly all farmed speciesPreventative technologies are constantly being

developedGood management and farming practices aid in

successParasites and pathogens are normal parts of

natural ecosystemsEradication = species extinction

= lack of natural community complexityFor the purposes of human sustenance

Limit disease in non-natural stocksBiosecurity