1 Institute of Aquaculture - University of Stirling Aquaculture Royal Veterinary College January...

1Institute of Aquaculture - University of Stirling

Aquaculture

Royal Veterinary CollegeJanuary 2004Jimmy Turnbull

Outline of the morning

Aquaculture Introduction to aquatic animal

healthAquatic animal disease diagnosis

and investigation Disease control and treatment

What is aquaculture?

Fisheries are a form of hunting Aquaculture is a form of farming

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/IntensificationGreat opportunities to travel

FAO 1995 Aquaculture = 23% of total aquatic prod.

Total aquatic production

Aquaculture

Fisheries

FAO 1995

Fisheries declining, aquaculture fastest growing food production sector

Aquaculture produced nearly 28 million

tonnesAquaculture more important in

developing and LIFD countries

FAO 1995

Million tonnes

Pigs Cattle Chickens Aquatic Sheep

Global meat production

Aquaculture + and -

Exhausted wild catches Food production vs use of fish meal

Food 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 tonnes/year

Example - Salmon life cylce

Fresh water

Value of ornamentals

World wholesale market £ 4,800 to 2,000 million

UK wholesale value £13 million (1994) UK retail value in

1990 = £203 million 1998 = £104.6 million

Ornamental fish exporters

Europe

16% Asia

5%Americas

Ornamental fish importers

Americas

33%Europe

1st USA2nd Japan3rd Germany4th UK

Value of ornamentals

Fish 3rd most popular pet after dogs and cats

35 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

DiagnosticiansHealth management / managementResearchTraining / teachingGovernment animal health controlDevelopment

Introduction to Aquatic Animal Health

JF TurnbullJF Turnbull

Why Study Aquatic disease?Why Study Aquatic disease?

A ccademic int er est

Control losses Prevent losses

I ncrease profi tability / secure livelihoods

I ncrease product ion

W hy study disease?

Costs of Poor HealthCosts of Poor Health

Loss of fish - mortalities Loss of production Loss of investor confidence Loss of opportunity Cost of control or

prevention Wild stock

Broodstock Fisheries

Loss of fish - mortalities Loss of production Loss of investor confidence Loss of opportunity Cost of control or

prevention Wild stock

Broodstock Fisheries

Health management and the system

The health of aquatic animals is more related to their environment and husbandry than in terrestrial animals

Diagnosis and control depend on an understanding of system

Unit of InterestUnit of Interest

Usually only interested in the population Not usually interested in the individual

Individuals only important as far as they relate to the population

Try to develop an idea of what is happening in the whole population

What is the population?

Usually only interested in the population Not usually interested in the individual

Individuals only important as far as they relate to the population

Try to develop an idea of what is happening in the whole population

What is the population?

Unit of InterestUnit of Interest

Population can be : Ponds, cage or tank Farms Areas of a country A whole region

EPIDEMIOLOGY you should know about this already

Population can be : Ponds, cage or tank Farms Areas of a country A whole region

EPIDEMIOLOGY you should know about this already

Host/Environment/PathogenHost/Environment/Pathogen

EnvironmentEnvironment

What can cause stress = anything!!!!

For example : Environment or management Nutrition Behaviour Other diseases Treatments

What can cause stress = anything!!!!

For example : Environment or management Nutrition Behaviour Other diseases Treatments

Very wide range of species Salmon and carp more different than

dog and cow

HostHost

Fish - inherent defences Normal microflora

Especially in the gut

Skin Stomach acid and gut

Carnivore vs herbivore

Fish - immunity Non-specific immunity Specific immunity

Fish - inherent defences Normal microflora

Especially in the gut

Skin Stomach acid and gut

Carnivore vs herbivore

Fish - immunity Non-specific immunity Specific immunity

Fish Skin

HostHost

Fish - Non-specific immunity Humoral - compounds in body

fluids Circulating cells Tissue-dwelling cells

Fish - Non-specific immunity Humoral - compounds in body

fluids Circulating cells Tissue-dwelling cells

Fish - Specific immunity Humoral - compounds in body

fluids Circulating cells

Lymphocytes - Antibody production Phagocytes - Phagocytosis and APC

HostHost

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

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

HostHost

Normal 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

Normal 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

PathogensPathogens

Same range of infectious pathogens as in mammals

viruses bacteria fungi protozoa metazoa

Same range of infectious pathogens as in mammals

viruses bacteria fungi protozoa metazoa

PathogenPathogen

Number of pathogens varies with : Number of sick animals Available nutrients

Access for pathogen to hosts Easier in aquatic environment

Terrestrial disease often in fluid blood, droplets, sexual

In aquaculture systems hosts concentrated

Number of pathogens varies with : Number of sick animals Available nutrients

Access for pathogen to hosts Easier in aquatic environment

Terrestrial disease often in fluid blood, droplets, sexual

In aquaculture systems hosts concentrated

PathogenPathogen

Pathogens

Examples WSD EUS Ich Salmon lice

Cause WSSV and other factorsMassive impact

US$600 million in Thailand in 1997Affects all systems

Extensive to Intensive

White Spot Disease (WSD)e (WSD)

E.U.S. outbreaksE.U.S. outbreaks

Aphanomyces invaderens

Non-infectious DiseaseNon-infectious Disease Nutritional

Proportion of nutrients e.g. Ca / P Deficiencies e.g. hypovitaminosis or malnutrition 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

Nutritional Proportion of nutrients e.g. Ca / P Deficiencies e.g. hypovitaminosis or malnutrition 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 Level 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: Non-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 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 Laboratory information e.g.

Fresh preparations Bacteriology Virology Histology Parasitology & others

Standard Growth Curve and Tolerance

Problems with diagnosis!

Identifying aquatic health is difficult Cannot see the animals

Abnormal behaviour Mortalities

Feeding often only 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

DiagnosisDiagnosis

Very similar to terrestrial animals

Identify 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

Very similar to terrestrial animals

Identify 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

Patterns 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? Propagating Point-source

Nutritional problems - PATTERN? Associations with risk factors

Significance of diagnosisSignificance 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 livelihood

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 livelihood

Methods to identify pathogensMethods 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

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 identify pathogens BUT the presence of the pathogen is not

the same as the presence of the disease

Few tests compared to terrestrial animals

Methods to identify pathogens

How many do you sample? < 1g = 10+ > 1g =6 ‘ish

PCR pls. approx’ 100

How do you obtain the fish or shrimp? Random sample e.g. from cast net Selected sample from sick

How many do you sample? < 1g = 10+ > 1g =6 ‘ish

PCR pls. approx’ 100

How do you obtain the fish or shrimp? Random sample e.g. from cast net Selected sample from sick

Methods to identify pathogensMethods 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

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 actionCourse of action

Do nothing May not be acceptable

Change management!!!!!!!!!!!

Kill fish Loss or emergency harvest Insurance and welfare

TREATMENT

Do nothing May not be acceptable

Change management!!!!!!!!!!!

Kill fish Loss or emergency harvest Insurance and welfare

TREATMENT

Management changes

May be all that is possible

Increase oxygenation Reduce exposure to carriers Improve hygiene

Cost benefit analysesCost benefit analyses

Cost of Drug Labour Lost production Withdrawal periods Mortalities resulting from

treatment Efficacy of treatment Political / legal and ethical

considerations

Verses benefit of treatmentRe-consider course of action

Cost of Drug Labour Lost production Withdrawal periods Mortalities resulting from

treatment Efficacy of treatment Political / legal and ethical

considerations

Verses benefit of treatmentRe-consider course of action

Cost benefit analyses 2/2Disease problem

Diagnosis Significance

Course of Action1. Nothing2. Change management3. Kill fish4. Treatment

Drug MethodCost 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

Check fish health Starve fish Trial therapy Check calculations Mix drug adequately

Beware of stock solutions

Ensure adequate O2

Dispose of waste carefully

TreatmentTreatment

Drug?Method of treatment?

Types of treatmentTypes of treatment

Immersion Flowing Flush Dip Bath

Immersion

Flowing

Bath Treatment in cages

No containment

Fish movement

Water currents

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 treatmentBath treatment

If it goes wrong Increase aeration Dilute drug or allow fish to escape from drug

Increase volumeIncrease flow

If it goes wrong Increase aeration Dilute drug or allow fish to escape from drug

Increase volumeIncrease flow

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

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

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/

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