Donald L. Dawe, DVM, PhD
Abstract
Immunization is evolving into an important method for controlling disease problems in fish. This paper will review the immune response in fish. The methods available and proposed for introducing antigens into fish will be considered. The problems of delivering antigens in appropriate forms and concentrations will be discussed. Also, factors influencing the ability of fish to respond to antigenic stimulation will be considered.
Notes
Methods of Disease Control
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Isolate sick fish, sanitize. Cycle water to keep it clean.
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Administer constant therapy (not best).
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Immunize
Immune Capabilities of Fish
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Cell-mediated response
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Nonspecific - very efficient - phagocytic cells. Inflammatory response exists, however, it is slower than for mammals (water temperature is low).
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Circulating immunoglobulins
Cyclostomes - Specific Agglutinins
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immunoproteins
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high molecular weight
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secondary response?
Elasmobranchs - Specific Immunoglobulins
Chondrostean - specific immunoglobulins 14s(6.5s) - tetramers
Teleosts - specific immunoglobulins
The anamnestic response in fish is slower and quantitatively lower compared to mammals. The duration of immunity in fish is not yet known. White blood cells of fish are produced in the haematopoietic tissue of the kidney.
Methods
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Inject
Advantages: stimulates sufficient circulating antibody
-- each fish gets a standard dose of antigen
Disadvantages- stress of handling difficult to do many fish.
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Oral
Advantages – Simple
Disadvantages - difficult to standardize dose of antigen
-- need long exposure to the antigen - antigen preparation is unstable.
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Water exposure
Advantages - Simple
Disadvantages-Need long exposure to antigen
-antigen unstable in water
-- the agent must multiply in fish in order to get adequate antigen production
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Osmotic exposure
Put fish in a hyperosmotic solution such as urea or salt. This causes the lymph sinus along the lateral line to react. The fish is then put in the antigenic solution and it will absorb the antigen.
Advantages - Simple
Disadvantages-only soluble antigens can be used.
-- Fish must be handled.
Present Immunization
Vibriosis- oral whole cell bacterin
IHN disease of Salmon - attenuated live virus in water.
Environmental factors affecting immunity
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Temperature
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Water quality - N products
--trace metals
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Population density
Passive immunity
The Amazonian discus fish secretes an antibody-containing mucus. The newly hatched fry feed on this and get passive immunity. It is possible that in future, immunization of breeding stock can be done.
The Amazonian discus fish secretes an antibody-containing mucus. The newly hatched fry feed on this and get passive immunity. It is possible that in future, immunization of breeding stock can be done.
Secretory immunoglobulins
These have been little studied. They may occur, giving surface protection against opportunists such as Ichthyophthirius. Oral immunization may stimulate secretory antibody as for example it does in TGE of piglets.