Transcript Disease agent

PRINCIPLES OF AQUACULTURE
(AKU3201)
Fish Diseases
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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
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1) Host susceptibility
• Physical barrier (skin, scales, exoskeleton, shell,
mucous membranes)
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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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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
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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
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Sick fish
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Unusual behaviour
Scrap body to wall
Coming to surface, gulping for air
Erratic swim
Loss appetite
Physical changes
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Diseases
• Exophthalmia (Pop-eye)
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• Extended belly
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• Haemorrhage
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2) Environment
• Crucial role in disrupting the balance between host
& pathogen
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Environmental stress => pathogen & host react
= disease occur
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Stress
Anoxia = absence of oxygen
Fright
Anaesthesia
Temperature changes
Injury
Pollution
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• High stocking density
• Restricted spaces – cages/tanks, raceway
• Large quantity of concentrated feeds/ fertilizer
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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
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• Temperature changes – fluctuation day & night
• Poikilothermic
Hatchery
- Closed system
- If temp. drops, used heater
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3) Disease agent
• Potential pathogens always present in aquatic
environment
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Disease agent
• Parasites (cestodes, nematodes, trematodes
& protozoans)
• Bacteria (vibriosis, edwardsiellosis,
furunculosis)
• Viruses (IPN, lymphocystis)
• Fungi (saprolegniasis, branchimycosis)
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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
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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
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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
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Protozoan: Ichthyopthirius multifiliis
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Copepod : Argulus, Lernaea
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Isopod (Sea lice)
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Monogenean parasites
Dactylogyrus
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Gyrodactylus
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Nematode
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2) Bacterial disease
• Vibriosis
- Vibrio harveyi
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• Vibrio anguillarum
• Vibrio alginolyticus
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Quorum sensing
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2) Bacterial quorum sensing
Quorum sensing (QS)
Monitor the environment & alter behaviour
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2) Bacterial quorum sensing
• Signal molecules
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OH
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AHL
(Found in 70 different G- bacterial species)
Diseases – controlled by QS
BHL
AHL
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• Aeromonas
- Aeromonas hydrophila
- Aeromonas salmonicida
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Furunculosis
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• Edwardsillosis
- Edwardsiella tarda
- Edwardsiella ictaluri
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• How to identify bacterial isolates
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Cotton swab
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Biochemical test
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Molecular techniques
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Serology
• ELISA (Enzyme-linked immunosorbent
assay)
Antigen – Antibody
Enzyme
= Sensitive method
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3) Viral disease
• Infectious pancreatic necrosis (IPN)
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Lymphocystis
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White spot
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4) Fungal disease
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Case study- Malaysia
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• Mass mortality June- August
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Spread of disease between country
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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
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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
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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
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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
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• Always monitor & record health status, water quality etc.
– corrective measures can be taken
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One trained person & basic facilities to undertake
regular health & environmental monitoring
- if expensive then twice a year inspection
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3) Disease treatment
• Chemotherapy – temporary, effect on biofiter
• Antibiotic – resistant bacteria
• Vaccines – specific to certain fish
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4) Sanitation
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Maintain good sanitation
Good culture practices
Monitor water supply –ozonation, UV, chlorination
Egg disinfection
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• Quarantine
– particularly to prevent the introduction of
communicable disease
- Facilities located away from farm
- Need to disinfect all facilities = chlorination
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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
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Vaccination
Immersion = small fish
Spray-shower = fish larger than 4g
Injection = intra-peritoneal
Retain immunity ~300 days
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6) Genetic resistance to disease
• Disease resistant strains through genetic
breeding
• Select strains with disease resistant
• High level of genetic diversity + hybrid vigour
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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
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Special care during transportation
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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
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• Quarantine new fish – check for pathogen
• Remove dead fish from system
• Dispose dead fish properly
• Good sanitation practices
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Ketapang leaves
Improve water quality
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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?
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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
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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
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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
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2) Provide a pathogen- free water source
- Mechanical filtration
- Chemical treatment
- UV filtration
- Ozonation
- Well- water
- Biological treatment
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Drum-filter = filtration of suspend solids in closed system
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Protein skimmer = remove dissolved organic matter in water
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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
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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
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First chlorine, then thiosulphate to nuetralize chlorine
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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)
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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
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Objective SPLAM
• Official recognition to aquaculture entrepreneurs
who have practiced GAP & environmental friendly
concepts
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