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Fish Diseases PRINCIPLES OF AQUACULTURE (AKU3201)
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HostEnvironment - Stocking density- Poor sanitation -Handling- Changes in pH, salinity -Transport temperature etc. -Chemotherapy -Nutrition -Behaviour Disease agent - Pathogen/ non-pathogen -Opportunistic pathogen Factors affecting fish health 3 Disease Host Disease agent Env
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Physical barrier (skin, scales, exoskeleton, shell, mucous membranes) 1) Host susceptibility 4
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Physical Signs Blistered areas Swollen bellies Popped-out eyes Bloody (hemorrhaged) areas on fins Discoloration or erosion of body parts Excessive mucus Growths on the body 5 Behavioral Signs Failure to feed properly Flashing (turning on their sides) Rubbing on the bottom Gathering around the water inflow Reduced vitality Gasping at the surface
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Physiological defences - Immune system, detoxification by liver -Nutritional well-being Age (Young more susceptible) Spawners – stress due to their reproductive functions 6
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Unusual behaviour -Scrap body to wall -Coming to surface, gulping for air - Erratic swim Loss appetite Physical changes Sick fish 7
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Exophthalmia (Pop-eye) Diseases 10
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Extended belly 11
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Haemorrhage 12
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Crucial role in disrupting the balance between host & pathogen Environmental stress => pathogen & host react = disease occur 2) Environment 17
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Stress -Anoxia = absence of oxygen -Fright -Anaesthesia -Temperature changes -Injury -Pollution 18
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High stocking density Restricted spaces – cages/tanks, raceway Large quantity of concentrated feeds/ fertilizer 19
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2) Environment 20 Do not exceed carrying capacity – stocking density Always monitor water quality Maintain proper DO, pH, alkalinity, temperature Check accumulation of organic debris, nitrogenous waste (ammonia, nitrite), hydrogen sulfide Remove pond bottom sludge, dry & lime
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21 Temperature changes – fluctuation day & night Poikilothermic Hatchery -Closed system -If temp. drops, used heater
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Potential pathogens always present in aquatic environment 3) Disease agent 22
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Parasites (cestodes, nematodes, trematodes & protozoans) Bacteria (vibriosis, edwardsiellosis, furunculosis) Viruses (IPN, lymphocystis) Fungi (saprolegniasis, branchimycosis) Disease agent 23
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Common entry point 1) Wound in skin Bacteria/viral infections => fungal infection 2)Gills Pathogen enter body through delicate & thin epithelium Protozoa establish themselves on them 3) Digestive tract Bacteria penetrate intestinal lining Protozoa 24
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Most common cause of fish mortalities Especially in larvae & fingerling stages Multiply rapidly without intermediate host Attach themselves to the host – special organ such as suckers 1) Parasites 25
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Penetrate host to multiply & invade vital organs Invade through ingestion, skin rupture, transgression of gill lamellae, penetration to the egg membrane 26
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Protozoan: Ichthyopthirius multifiliis 27
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Copepod : Argulus, Lernaea 28
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Isopod (Sea lice) 29
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Monogenean parasites 30 Dactylogyrus
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31 Gyrodactylus
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Nematode 32
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Vibriosis - Vibrio harveyi 2) Bacterial disease 33
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Vibrio anguillarum Vibrio alginolyticus 34
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Quorum sensing 35
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Monitor the environment & alter behaviour 2) Bacterial quorum sensing Quorum sensing (QS) 36
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Signal molecules 2) Bacterial quorum sensing Diseases – controlled by QS AHL 37 (Found in 70 different G- bacterial species) BHL AHL
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Aeromonas -Aeromonas hydrophila -Aeromonas salmonicida 39
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Furunculosis 40
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Edwardsillosis -Edwardsiella tarda -Edwardsiella ictaluri 41
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How to identify bacterial isolates 42
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Cotton swab 43
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Biochemical test 47
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Molecular techniques 48
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ELISA (Enzyme-linked immunosorbent assay) Serology 50 Antigen – Antibody Enzyme = Sensitive method
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Infectious pancreatic necrosis (IPN) 3) Viral disease 51
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Lymphocystis 52
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White spot 53
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4) Fungal disease 55
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Case study- Malaysia 60
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Mass mortality June- August 61
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Import- export Exotic disease Stress during transport Fish weak & susceptible to disease How to overcome 1)Discourage/ ban import of live fish 2)Quarantine & sterilize the fish 3)Purchase from reliable source 4)Seed free from disease Spread of disease between country 62
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Spread of disease in pond/cages -Through water channel -Spread pond to pond -No barrier -Water current -Dead fish thrown into open waters -Other animals as carrier -Equipments 64
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1) Integrated health management 2) Health inspection & disease monitoring 3) Disease treatment 4) Sanitation 5) Immunization 6) Genetic resistance to disease 7) Farm disinfection Solution to fish disease 65
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Guidelines for prevention, control & eradication Correction of disease-causing & disease spreading conditions Adoption & implementation of policies & regulations by the state – need cooperative effort 1) Integrated health management 66
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Always monitor & record health status, water quality etc. – corrective measures can be taken One trained person & basic facilities to undertake regular health & environmental monitoring - if expensive then twice a year inspection 2) Health inspection & disease monitoring 67
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Chemotherapy – temporary, effect on biofiter Antibiotic – resistant bacteria Vaccines – specific to certain fish 3) Disease treatment 68
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Maintain good sanitation Good culture practices Monitor water supply –ozonation, UV, chlorination Egg disinfection 4) Sanitation 69
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Quarantine – particularly to prevent the introduction of communicable disease - Facilities located away from farm -Need to disinfect all facilities = chlorination 71
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Mechanism of antibody production Antibody = specific immunoglobulin (modified protein) produced in response to & reacts specifically with an antigen (foreign substance that stimulate the formation of antibodies) Vaccines contains antigens that are generally attenuated or killed disease agents. When administered to a host, they stimulate the production of specific antibodies or non-specific resistance to that particular disease agent 5) Immunization 72
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Vaccination -Immersion = small fish -Spray-shower = fish larger than 4g -Injection = intra-peritoneal -Retain immunity ~300 days 73
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Disease resistant strains through genetic breeding Select strains with disease resistant High level of genetic diversity + hybrid vigour 6) Genetic resistance to disease 74
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Disease outbreak = Farmer destroy stock & disinfect rearing facilities Easier fro small, well-controlled facilities e.g., hatcheries, tank, raceways. Earthern pond = difficult 7) Farm disinfection 75
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During transportation -Minimize physical injury – use smooth net -Avoid sharp edge tank -Stop feeding 12-24h to reduce metabolism & excretion - Provide high oxygen level - Salt at 0.3-1% to minimize osmotic stress -Anesthesia if necessary -Put bag into Styrofoam box -Acclimatization- bag left floating for 30 minutes Special care during transportation 76
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Quarantine new fish – check for pathogen Remove dead fish from system Dispose dead fish properly Good sanitation practices 77
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Ketapang leaves 79
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Improve water quality o 80
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Biosecurity= Steps taken to keep disease from a farm & to prevent the transmission of disease within an infected farm to neighboring farm. Consideration on initial facility layout design Breeder => hatchery => growout (need to ensure biosecurity measures) Need to have SOP Isolation, sanitation & control Closed system Open system? Biosecurity 81
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1)Reduce the risk of disease introductions 2)Minimise the spread of diseases on-farm or to new areas 3)Promote fish health 4)Protect economic investment 5)Protect human health Biosecurity 82
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1)Avoid the introduction of certain pathogens into an aquaculture facilities a)Purchase from a producing selling certified specific pathogen-free (SPF) stock b)SPF = special stock of animals that are kept in specific pathogen free facilities under rigorious monitoring system c) Problem: Only few spp. of SPF e.g. shrimp -Shrimp have primitive immune system -No workable vaccine Biosecurity 83
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d) Tilapia & Pangasius no SPF but have vaccine e) Vaccinated Pathogen Free seed-stock (VPF) VPF = Fish vaccinated when they are healthy & before exposure to the nature f) Have own in house broodstock/spawning facilities g) Have a quarantine/ isolation facilities 84
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2) Provide a pathogen- free water source -Mechanical filtration -Chemical treatment -UV filtration -Ozonation -Well- water -Biological treatment 85
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Drum-filter = filtration of suspend solids in closed system 87
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Protein skimmer = remove dissolved organic matter in water 88
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3) Disease monitoring -Always monitor for clinical signs of disease -Regular scheduled health evaluation -Sampled for diagnostic health techniques -Treat if warranted 89
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4) Disinfection - Strict adherence to cleaning & disinfection techniques -Foot bath & hand wash -Container with disinfectant for nets etc. -Separate equipments (nets, feed bucket) -Disinfect vehicles -E.g disinfectant = Hypochlorite -Maintain good husbandry practices 90
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First chlorine, then thiosulphate to nuetralize chlorine 92
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Good aquaculture practices (GAP) -Improved production, food safety assurance & preservation of environments Hazard Analysis Critical Control Point (HACCP) Standard sanitation & operating procedures (SSOP) 94
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Malaysian Aquaculture Farm Certification Scheme Sijil Pensijilan Ladang Akuakultur Malaysia (SPLAM) -Encourage Good Aquaculture Practice & emphasize implementation of HACCP - Aquaculture entrepreneurs need to fulfill requirements & criteria set by DOF -Make application, undergo a review audit & final approval - Valid for two years SPLAM 95
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Official recognition to aquaculture entrepreneurs who have practiced GAP & environmental friendly concepts Objective SPLAM 96
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