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Transcript
PRINCIPLES OF AQUACULTURE (AKU3201) Fish Diseases 1 2 3 Factors affecting fish health Host - Stocking density - Handling - Transport - Chemotherapy - Nutrition - Behaviour Environment - Poor sanitation - Changes in pH, salinity temperature etc. Disease agent - Pathogen/ non-pathogen - Opportunistic pathogen Disease agent Env Host Disease 4 1) Host susceptibility • Physical barrier (skin, scales, exoskeleton, shell, mucous membranes) 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 • • • • • • Physical Signs Blistered areas Swollen bellies Popped-out eyes Bloody (hemorrhaged) areas on fin Discoloration or erosion of body parts • Excessive mucus • Growths on the body 6 • Physiological defences - Immune system, detoxification by liver - Nutritional well-being • Age (Young more susceptible) • Spawners – stress due to their reproductive functions 7 Sick fish • • • Unusual behaviour Scrap body to wall Coming to surface, gulping for air Erratic swim Loss appetite Physical changes 8 9 10 Diseases • Exophthalmia (Pop-eye) 11 • Extended belly 12 • Haemorrhage 13 14 15 16 17 2) Environment • Crucial role in disrupting the balance between host & pathogen • Environmental stress => pathogen & host react = disease occur 18 • - Stress Anoxia = absence of oxygen Fright Anaesthesia Temperature changes Injury Pollution 19 • High stocking density • Restricted spaces – cages/tanks, raceway • Large quantity of concentrated feeds/ fertilizer 20 2) Environment • 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 21 • Temperature changes – fluctuation day & night • Poikilothermic Hatchery - Closed system - If temp. drops, used heater 22 3) Disease agent • Potential pathogens always present in aquatic environment 23 Disease agent • Parasites (cestodes, nematodes, trematodes & protozoans) • Bacteria (vibriosis, edwardsiellosis, furunculosis) • Viruses (IPN, lymphocystis) • Fungi (saprolegniasis, branchimycosis) 24 • 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 25 1) Parasites • 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 26 • Penetrate host to multiply & invade vital organs • Invade through ingestion, skin rupture, transgression of gill lamellae, penetration to the egg membrane 27 Protozoan: Ichthyopthirius multifiliis 28 Copepod : Argulus, Lernaea 29 Isopod (Sea lice) 30 Monogenean parasites Dactylogyrus 31 Gyrodactylus 32 Nematode 33 2) Bacterial disease • Vibriosis - Vibrio harveyi 34 • Vibrio anguillarum • Vibrio alginolyticus 35 Quorum sensing 36 2) Bacterial quorum sensing Quorum sensing (QS) Monitor the environment & alter behaviour 37 2) Bacterial quorum sensing • Signal molecules O O OH O N H AHL (Found in 70 different G- bacterial species) Diseases – controlled by QS BHL AHL 38 39 • Aeromonas - Aeromonas hydrophila - Aeromonas salmonicida 40 Furunculosis 41 • Edwardsillosis - Edwardsiella tarda - Edwardsiella ictaluri 42 • How to identify bacterial isolates 43 Cotton swab 44 45 46 47 Biochemical test 48 Molecular techniques 49 50 Serology • ELISA (Enzyme-linked immunosorbent assay) Antigen – Antibody Enzyme = Sensitive method 51 3) Viral disease • Infectious pancreatic necrosis (IPN) 52 Lymphocystis 53 White spot 54 55 4) Fungal disease 56 57 58 59 60 Case study- Malaysia 61 • Mass mortality June- August 62 Spread of disease between country • • • • 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 63 64 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 65 Solution to fish disease 1) Integrated health management 2) Health inspection & disease monitoring 3) Disease treatment 4) Sanitation 5) Immunization 6) Genetic resistance to disease 7) Farm disinfection 66 1) Integrated health management • Guidelines for prevention, control & eradication • Correction of disease-causing & disease spreading conditions • Adoption & implementation of policies & regulations by the state – need cooperative effort 2) Health inspection & disease monitoring 67 • 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 68 3) Disease treatment • Chemotherapy – temporary, effect on biofiter • Antibiotic – resistant bacteria • Vaccines – specific to certain fish 69 4) Sanitation • • • • Maintain good sanitation Good culture practices Monitor water supply –ozonation, UV, chlorination Egg disinfection 70 71 • Quarantine – particularly to prevent the introduction of communicable disease - Facilities located away from farm - Need to disinfect all facilities = chlorination 72 5) Immunization • 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 73 • - Vaccination Immersion = small fish Spray-shower = fish larger than 4g Injection = intra-peritoneal Retain immunity ~300 days 74 6) Genetic resistance to disease • Disease resistant strains through genetic breeding • Select strains with disease resistant • High level of genetic diversity + hybrid vigour 75 7) Farm disinfection • Disease outbreak = Farmer destroy stock & disinfect rearing facilities • Easier fro small, well-controlled facilities e.g., hatcheries, tank, raceways. • Earthern pond = difficult 76 Special care during transportation • - 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 77 • Quarantine new fish – check for pathogen • Remove dead fish from system • Dispose dead fish properly • Good sanitation practices 78 79 Ketapang leaves Improve water quality o 80 81 Biosecurity • 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? 82 Biosecurity 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 83 Biosecurity 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 84 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 85 2) Provide a pathogen- free water source - Mechanical filtration - Chemical treatment - UV filtration - Ozonation - Well- water - Biological treatment 86 87 Drum-filter = filtration of suspend solids in closed system 88 Protein skimmer = remove dissolved organic matter in water 89 3) Disease monitoring - Always monitor for clinical signs of disease - Regular scheduled health evaluation - Sampled for diagnostic health techniques - Treat if warranted 90 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 91 92 First chlorine, then thiosulphate to nuetralize chlorine 93 94 • Good aquaculture practices (GAP) - Improved production, food safety assurance & preservation of environments • Hazard Analysis Critical Control Point (HACCP) • Standard sanitation & operating procedures (SSOP) 95 SPLAM • 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 96 Objective SPLAM • Official recognition to aquaculture entrepreneurs who have practiced GAP & environmental friendly concepts 97