Use Of Immunostimulants In Aquaculture Systems
Sajid Maqsood*, Prabjeet Singh, Munir Hassan Samoon and Gohar Bilal Wani.
Faculty of Fisheries, Sher-e-Kashmir University of
Agricultural Science and Technology-Kashmir, India.
*Corresponding author E-mail : email@example.com.
The contribution of aquaculture to fish production is steadily
increasing. The increase would have been much more but for the major
constraint of loses in culture production, particularly of shrimp,
due to diseases. In India, the loss of shrimp production during
1995-96 due to diseases is estimated to be Rs.600 crores and the
loses continue around this level sine then. Loses in production of
cultured shrimp have led to the realization that the goal of
aquaculture is not merely to increase production but to make it
sustainable. In recent years the application of vaccination in
respect to finfish and immunostimulants in respect of shrimp/finfish
for disease management in aquaculture is being increasingly
recognized. Generally, immunostimulants enhance individual components
of the non specific immune response but this does not always
translate into increased survival. I addition, immunostimulants fed
at too high dose or for too long can be immunosuppressive.
The substances of capable of stimulating immune response are the
compounds that promote release of from immune effecter cells.
Immunostimulants enhance the humoral and cellular response in both
specific and non-specific ways. These agents are widely used for
impaired immune function and to stabilize the improved immune status.
The use of immunostimulants in fish culture or in aquaculture of
other species for prevention of diseases is a promising new
development. In general, immunostimulants comprise a group of
biological and synthetic compounds that enhance the non-specific
defense mechanisms in animals, thereby imparting generalized
protection. This protection may be particularly important for fish
that are raised in or released into environments where the nature of
pathogen is unknown and immunization by specific vaccine may be
futile. Several immunostimulants have been evaluated in fin fishes.
Many occasions arise in the course of fish culture that calls for
enhancement of immune response. These include strengthening of the
normal immune response in order to enhance protection and reduce
immunosuppressive conditions. Immunostimulants can be classified into
several categories by their origin and mode of action—
bacteria and bacterial products,
immunity enhancing drugs,
Lectins, plant extracts.
Two main procedures for evaluating the efficiency of an
In vivo, eg., protection tests against fish pathogens: and
In vitro, eg, measurement of the efficiency of cellular and
humoral immune mechanism.
Attention is focused on the lymphocyte proliferation test as an
adequate method for providing a correct evaluation of the cellular
immune condition which can be adopted together with the more commonly
used parameters, such as phagocytosis and respiratory burst. It may
be mentioned here that the use of immunostimulants in the diets of
marine fish and the evaluation of their effect on the immune system
of fish has been investigated.
As immunostimulants, as such, which can be useful in preventing
diseases in land based aquaculture, in pens and hatcheries rarely
occurs alone in the natural environment, the subject deserves a
Specific and non-specific immunostimulants:
Specific immunostimulation is related to the potentiation of the
host's immune system towards a unique specific antigen. Vaccination
is perhaps the best example of producing specific immunity.
Non specific immunostimulation generally is an attempt to upgrade
immunologic capabilities at a time when an animal may be exposed to
one or several pathogens and/or be immuno-compromised.
Characteristics of an ideal immunostimulants:
These can be described as:
It should be non-toxic, even at a high dose rate.
It should be non-carcinogenic or have long term side effects.
At therapeutic levels, it should have a short withdrawal period with
low tissue residues.
It should stimulate a wide range of non-specific immune responses
against bacteria, fungi, virus, protozoa and helminthes.
It should be capable of amplifying primary and secondary immune
responses to infectious agents.
Breakdown products of compound concerned should be either inactive
or readily biodegradable in the environment.
It should be having defined chemical composition or biological
It should be active by oral route and should be stable both in its
native state and after incorporation into food and water.
It should be compatible with arrange of drugs including antibiotics
and anthelmintics, and
It should be inexpensive and either tasteless or palatable.
Objectives of immunostimulation:
Promoting a greater and more effective sustained immune response to
those infectious agents producing subclinical disease without risks
of toxicity, carcinogenicity or tissue residues.
Hastening the maturation of non-specific and specific immunity in
young susceptible animals.
Enhancing the level of duration of specific immune response, both
cell mediated and humoral, following vaccination.
Overcoming of immunosuppressive effects of stress and of those
infectious agents that damage or interface with the functioning of
cells of immune system.
Selectively stimulating the relevant components of the immune system
or non-specific immune mechanism that preferentially confer
protection against micro-organisms. For example via interferon
release, especially for those infectious agents for which no
vaccines currently exists; and
Maintaining immune surveillance at hightened level to ensure early
recognition and elimination of neoplastic changes in tissues.
Some common immunostimulants:
Muramyl dipeptide: Muramyl dipeptide is a simple glycoprotein,
also a purified form of mycobacteria. Its activity includes:
Enhancement of antibody activity.
Stimulation of polyclonal activation of lymphocytes, and
Activation of macrophages.
Levamisole: It is an anthelmintics chemical that has been
shown to have some stimulating effect on the immunological reactivity
of animals and humans. Activities of this agent are:
enhancement of cell mediated cytotoxicity, lymphokine production and
suppressor cell function, and
Stimulation of pathagocytic activity of macrophages and neutrophils.
Glucans: Glucans are the most popular immunostimulants used in
aquaculture. It is derived from yeast cell wall and from certain
higher plants. It has excellent immunostimulatory properties and
works well when injected or fed to fish.
Yano et al. (1991) showed that Î3-1, 6, branched Î3-1, 3 Glucans were
effective in carp. Jenny and Anderson (1993) showed that the use of
Glucans increased activity in non-specific defense mechanism and in
protection against Yesinia ruckeri. Glucan treatment of
Atlantic salmon (salmo salar) induced protection against
Vibrio salmonicidia. Several Glucan products such as
vitastim, macrogard, are marketed commercially and are used in
supplementing fish feeds.
Chitin and chitosan: Both chitin and chitosan have a major
role in aquaculture. They are non-specific immunostimulators which
are effective on a short term basis. Anderson & Swicki (1994)
administered chitosan to brook trout (Salvenus fontinalis) by
injection and immersion and found that high levels of protection
occurred 1, 2, 3 days afterwards, but protection was greatly reduced
by day 14. Injection of chitosan was also more effective than simple
Actually chitosan is a deacetylation product of chitin. The influence
of chitosan on immune response of healthy and cortisol treated rohu
was demonstrated. After treatment with chitosan sufficiently higher
responses in almost all assays of non-specific immunity was observed
in comparison to their healthy control or cortisol treated
counterparts respectively without chitosan treatment (Sahoo and
Mukherjee, 1999). In aquaculture, chitosan has been used as an
immunostimulant for protection against bacterial disease in fish, for
controlled release of vaccines, and as a diet supplement (Bullock et
al., 2000). Similar dose of chitosan in brook trout has been shown to
be immunopotent. It had a higher degree of protection against A.
salmonicida infection for a short duration. It also gave
protection when feeding was done @ 0.5 gm/100gm feed for one week.
Vitamin C and E: both the vitamins are antioxidants. Vitamin C
acts as a multiple cell stimulator. Diet supplemented with vitamin C
gave protection against A. salmonicida in Atlantic salmon.
Vitamin E stimulates B and T lymphocytes: The mode of action
of vitamin E in enhancing immunity is nuclear but it has been found
that supplemental vitamin E may serve as a significant stimulus of
immunity in some individuals.
Bacillus Calmette Guarine (BCG): It is a potent cytokine
synthesis enhancer. It is actually a live attenuated vaccine strain
of Mycobacterium bovis. BCG produces a generalized enhancement of
both B cell and T cell mediated responses of phagocytosis and
resistance to infection.
Streptococcal components: These components are potent
immunostimulants. Products from Bordetella pertuosis, Brucella
abortus, Bacillus subtilis and Klebsiella pneumoniae all
have immunostimulating activities.
Acemannan: It is a complex carbohydrate. It is a potent
cytokine synthesis enhancer with anti-tumor and anti-viral
activities. It also has the important property of stimulating wound
Lentinan: It is a polysaccharide extracted from a comestible
mushroom. Lentinus elodes is endowed with anti-tumor activity.
Lentinan might act by increasing sensitivity to histamine and
Leaf extract of Ocimum sanctum: Effect of leaf extract Ocimum
the specific and non-specific immune responses and
Disease resistance against Aeromonas hydrophila was
investigated in Oreochromis mossambicus.
It stimulated both antibody response and neutrophil activity. Dietary
intake also enhances the antibody response and disease resistance to
Aeromonas. Possibility of using O. sanctum as
immunostimulant is used in the maintenance of finfish health in
intensive freshwater aquaculture/
C-UP 111: It has immunostimulant activating leucocyte
functions. Highest preventive effect has been shown against Aeromonas
infection in Nile tilapia with improved neutrophil function, in
comparison with Glucans and lactoferin. It is the most popular agent
in aquaculture system.
Aquatim: This is a kind of immunostimulant developed by the
department of Microbiology of the College of Fisheries, Mangalore and
now manufactured and marketed by Mangalore Biotech Laboratory,
Mangalore under this trade name. It is widely marketed in India,
particularly in Karnataka and Goa.
Aerobic coryneforms: Propionebacterium acenes promotes
antibody formation when administered as a killed suspension. This
bacteria is phagocytosed by macrophage and stimulates cytokine
synthesis. This organism has a general immunostimulating action
leading to enhanced antibacterial and antitumor activity.
Anderson DP, Swicki AK. 1994. Duration of protection against
Aeromonas salmonicida in brook trout immunostimulated with glucan or
chitosan by injection or immersion. Progres. Fish Cul. 56: 258-261.
Bullock G, Blazer V, Tsukuda S, Summerfelt S. 2000. Toxicity of
acidified chitosan for cultured rainbow trout (Oncorhynchus
mykiss). Aquacul. 185 (3-4): 272-280.
Jeney G, Anderson DP. 1993a. Enhanced immune response and protection
in rainbow trout to Aeromonas salmonicida bacterin following
prior immersion in immunostimulants. Fish. Shellfish. Immunol. 3(1):
Sahoo PK, Mukherjee SC. 1999. Influence of the immunostimulant,
chitosan on immune responses of healthy and cortisol-treated rohu
(Labeo rohita). J. Aquacul. Tropics 14 (3): 209-215.
Yano T, Matsuyama H, Mangindann, REP. 1991. Polysaccharide- induced
protection of carp, Cyprinus carpio against bacterial
infection. J. Fish Dis. 14:
Seafood — Fish — Crustacea
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