1、Aquaculture,Royal Veterinary College January 2004 Jimmy Turnbull,Outline of the morning,Aquaculture Introduction to aquatic animal health Aquatic animal disease diagnosis and investigation Disease control and treatment,What is aquaculture?,Fisheries are a form of hunting Aquaculture is a form of far
2、ming Any type of aquatic animal or plant Seaweed, mussels, shrimps, fish, crocodiles etc,Aquaculture,Huge industry / source of livelihoods 75% of population in some of SE Asia Very diverse Climate/Water source/Species/ Systems/Intensification Great opportunities to travel,FAO 1995,Aquaculture = 23%
3、of total aquatic prod.,FAO 1995,Fisheries declining, aquaculture fastest growing food production sector Aquaculture produced nearly 28 million tonnes Aquaculture more important in developing and LIFD countries,FAO 1995,Aquaculture + and -,Exhausted wild catches Food production vs use of fish meal Fo
4、od security Low cost high quality food vs export orientated production Food safety High quality protein and lipid vs chemical residues Environment Sustainable resource vs pollution,Size and value of aquaculture,UK Atlantic salmon industry 120,000 tonnes/year 300 million 1999 World production 472,000
5、 tonnes/year,Example - Salmon life cylce,Fresh water,Sea,Value of ornamentals,World wholesale market 4,800 to 2,000 millionUK wholesale value 13 million (1994) UK retail value in 1990 = 203 million 1998 = 104.6 million,1st USA 2nd Japan 3rd Germany 4th UK,Value of ornamentals,Fish 3rd most popular p
6、et after dogs and cats35 to 40 million fish imported / year 1,000 tropical species 20 cold water species Fish = 75% of airlines livestock income,Role of vets in aquaculture,Diagnosticians Health management / management Research Training / teaching Government animal health control Development,Introdu
7、ction to Aquatic Animal Health,JF Turnbull,Why Study Aquatic disease?,Costs of Poor Health,Loss of fish - mortalitiesLoss of productionLoss of investor confidenceLoss of opportunityCost of control or preventionWild stock Broodstock Fisheries,Health management and the system,The health of aquatic ani
8、mals is more related to their environment and husbandry than in terrestrial animalsDiagnosis and control depend on an understanding of system,Unit of Interest,Usually only interested in the population Not usually interested in the individual Individuals only important as far as they relate to the po
9、pulation Try to develop an idea of what is happening in the whole population What is the population?,Unit of Interest,Population can be : Ponds, cage or tank Farms Areas of a country A whole regionEPIDEMIOLOGY you should know about this already,Host/Environment/Pathogen,Over used and abused,Environm
10、ent,What can cause stress = anything!For example : Environment or management Nutrition Behaviour Other diseases Treatments,Host,Very wide range of species Salmon and carp more different than dog and cow,Host,Fish - inherent defences Normal microflora Especially in the gut Skin Stomach acid and gut C
11、arnivore vs herbivore Fish - immunity Non-specific immunity Specific immunity,Fish Skin,Host,Fish - Non-specific immunity Humoral - compounds in body fluids Circulating cells Tissue-dwelling cells,Host,Fish - Specific immunity Humoral - compounds in body fluids Circulating cells Lymphocytes - Antibo
12、dy production Phagocytes - Phagocytosis and APC,Host,Normal defences are labile, subject to Endogenous changes Moulting in crustaceans Reproductive state, especially in salmonids Skin, gut, cardiovascular, immune system Genetics - resistant strains not successful Immunity Immunomodulation,Host,Norma
13、l defences are labile, subject to Exogenous factors : Nutrition Environment esp temperature Degree days Growth Immune response Inflammation Healing - skin less affected Growth of tumours Physical damage,Pathogens,Same range of infectious pathogens as in mammals viruses bacteria fungi protozoa metazo
14、a,Pathogen,Number of pathogens varies with : Number of sick animals Available nutrientsAccess for pathogen to hosts Easier in aquatic environment Terrestrial disease often in fluid blood, droplets, sexual In aquaculture systems hosts concentrated,Pathogen,Pathogens,Examples WSD EUS Ich Salmon lice,C
15、ause WSSV and other factors Massive impact US$600 million in Thailand in 1997 Affects all systems Extensive to Intensive,White Spot Disease (WSD),E.U.S. outbreaks,1998,Aphanomyces invaderens,Non-infectious Disease,Nutritional Proportion of nutrients e.g. Ca / P Deficiencies e.g. hypovitaminosis or m
16、alnutrition Excesses of nutrient e.g. hypervitaminosis Toxic compounds e.g. rancid fats, fungal toxins etc. Environmental Too much e.g. ammonia Too little e.g. O2 Genetic/congenital Increased susceptibility to infections,Why deal with populations?,Lab experiments cannot be generalised to the farm Le
17、vel of immune stimulation Will differ between lab and farm Field challenges may (will) differ from experimental challenges May be unpredictable effects,Why deal with populations?,(continued) Large populations have inherent and unpredictable dynamics as a result of : Sum of individual variation in: N
18、on-specific defence mechanisms Response to stress, Level of pre-existing immunostimulation Inherent population effects including : Proportion infected and Rate of transmission,Why deal with populations?,Without field trial data You cannot advise on : The magnitude of any benefits vs costs How to use
19、 treatment for best results The treatment is a gamble Improved chance of success or Another cost with no return,Aquatic animal disease Diagnosis and Investigation,Jimmy Turnbull,Diagnoses,Need to look at a range of information Clinical signs e.g. behaviour, appearance Production information Laborato
20、ry information e.g. Fresh preparations Bacteriology Virology Histology Parasitology & others,Standard Growth Curve and Tolerance,Standard Growth Curve and Tolerance,Problems with diagnosis!,Identifying aquatic health is difficult Cannot see the animals Abnormal behaviour Mortalities Feeding often on
21、ly time to observe Clinical signs not much use,Problems with diagnosis!,Clinical signs / examination not very useful Farmers may use CS to spot a problem Cannot often use CS to diagnose a problem Aquatic animals limited capacity to express CS Same CS different disease or same disease different CS,Di
22、agnosis,Very similar to terrestrial animalsIdentify and determine cause of problem Presented information - often misleading History PATTERN OF THE DISEASE Species / age / No affected / Groups affected / Onset / Duration / Clinical signs / Previous diseases / Treatments General farm information,Patte
23、rns of disease,Patterns one of the most important aspects Should lead to useful interventions Spread over time and geographically Associations with : Environmental events Batches of seed Batches of feed,Patterns of disease,Sudden acute sever mortality - CAUSES? Infectious problems - PATTERN? Propaga
24、ting Point-source Nutritional problems - PATTERN? Associations with risk factors,Significance of diagnosis,Significance of the diagnosis Are there other problems? Which is the most important of the problems? What is the underlying cause? What is the impact of the disease On profitability On liveliho
25、od,Methods to identify pathogens,All techniques used to identify pathogens have some very serious practical limitations Cannot sample a large enough proportion of the animals Difficult to get representative samples Test always have limitations,Diagnostic tests - no such thing!,There are tests to ide
26、ntify pathogens BUT the presence of the pathogen is not the same as the presence of the diseaseFew tests compared to terrestrial animals,Methods to identify pathogens,How many do you sample?1g =6 ish PCR pls. approx 100 How do you obtain the fish or shrimp? Random sample e.g. from cast net Selected
27、sample from sick,Methods to identify pathogens,Test limitations False negatives (sensitivity) False positives (specificity) Best tests including PCR 95% sensitive and specific Get 5% false negatives and 5% false positives,Health Control and Treatment,JF Turnbull,Course of action,Do nothing May not b
28、e acceptable Change management! Kill fish Loss or emergency harvest Insurance and welfare TREATMENT,Management changes,May be all that is possibleIncrease oxygenation Reduce exposure to carriers Improve hygiene,Cost benefit analyses,Cost of Drug Labour Lost production Withdrawal periods Mortalities
29、resulting from treatment Efficacy of treatment Political / legal and ethical considerations Verses benefit of treatment Re-consider course of action,Cost benefit analyses 2/2,Disease problem,Diagnosis,Significance,Course of Action 1. Nothing 2. Change management 3. Kill fish 4. Treatment,Drug,Method
30、,Cost benefit analyses,ACTION,Treatment - general precautions,Check fish health Starve fish Trial therapy Check calculations Mix drug adequately Beware of stock solutions Ensure adequate O2 Dispose of waste carefully,Treatment,Drug? Method of treatment?,Types of treatment,Immersion Flowing Flush Dip
31、 Bath,Immersion,Flowing,Flush,Bath Treatment in cages,No containment,Curtain 1/3,Curtain 2/3,Curtain 3/3,Full bag 1/6,Full bag 2/6,Full bag 3/6,Full bag 4/6,Full bag 5/6,Full bag 6/6,Bath treatment,If it goes wrong Increase aeration Dilute drug or allow fish to escape from drug Increase volume Incre
32、ase flow,Types of treatment,In feed Usually antibiotics Reduce total feed and top up if necessary Medicated food spread throughout the day Mixing Surface coating Incorporation at mill Volume Time,Types of treatment,Topical Injection,Thank you http:/staff.stir.ac.uk/j.f.turnbull/,http:/www.aquaculture.stir.ac.uk These lectures and other links are on http:/staff.stir.ac.uk/j.f.turnbull/,
