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Prophylactic Measures Used In Aquaculture

Smit lende1, Vishnu brahmane2

1.Dept. Of Aquaculture 2.Dept Of Fisheries Resource Manegment

College of fisheries science

Veraval JAU Gujrat



Introduction

World aquaculture has grown tremendously during the last years becoming an economically important industry (Subasinghe et al., 2009). Today it is the fastest growing food-producing sector in the world with the greatest potential to meet the growing demand for aquatic food (FAO 2006). Globally, aquaculture is expanding into new directions, intensifying and diversifying. A persistent goal of global aquaculture is to maximize the efficiency of production to optimize profitability.

 However, disease is a primary constraint to the growth of many aquaculture species and is now responsible for severely impeding both economic and socio-economic development in many countries of the world. Disease caused by Vibrio spp. and Aeromonas spp. Are commonly episodes of mortality. When faced with disease problem the common response has been to turn to following prophylactic measures.

The following components are undertaken in prophylactic measurre for disease prevention in aquaculture ;

  1. Prebiotics

  2. Probiotics

  3. Vaccine

  4. Immunostimulants

Prebiotic

Prebiotics are a non digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon and thus improves host health.(Gibson and Roberfroid, 1995). In different studies since 1999, many substances have been investigated as prebiotic. Based on the study of Mahious and Ollevier (2005), Fooks et al. (1999), and Gibson et al. (2004), any foodstuff that reaches the colon, e.g. non-digestible carbohydrates, some peptides and proteins, as well as certain lipids, is a candidate prebiotic.

Certain non-digestible carbohydrates seem authentic prebiotics. They include resistant inulin and oligofructose, transgalactooligosaccharides (TOS), lactulose, isomalto oligosaccharides (IMO), lactosucrose, xylo-oligosaccharides (XOS), soyabean oligosaccharides and glucooligosaccharides. From in vivo and in vitro studies, inulin and oligofructose, TOS and lactulose are presently classified as prebiotics. IMO, lactosucrose, XOS, soyabean oligosaccharides and glucooligosaccharides are not considered as functional ingredients since they do not fulfill all criteria for classification as prebiotics. Prebiotics are selectively fermented by Bifidobacteria, Lactobacillus and Bacteroides. Inclusion of prebiotic in the diet has been reported to increase the uptake of glucose (Breves et al., 2001) and bioavailability of trace elements (Bongers and van den Heuvel, 2003).

In later use of prebiotics, they have the binding capacity therefore increasing the absorption of mineral such as calcium, magnesium and iron; these minerals, are not absorbed in the small intestine and so reach the colon, where they are released from the carbohydrate matrix and absorbed.

Prebiotics have been reported to have numerous beneficial effects in fish such as increased disease resistance and improved nutrient availability. The reasons for the different results are not clear yet. It may be due to the different basal diet, inclusion level, type of omnosaccharide, adaptation period, chemical structure (degree of polymerization, linear or branched, type of linkages between monometric sugars), origin of prebiotic, animal characteristics (species, age, and stage of production), duration of use and hygienic conditions of the experiment. If beneficial effects of prebiotics are manifested in fishes, then prebiotics have much potential to increase the efficiency and sustainability of aquacultural production. Therefore, comprehensive research to more fully characterize the intestinal microbiota of prominent fish species and their responses to prebiotics is warranted. and survival.

  1. Probitics

The origin of the term probiotic is attributed to Parker (1974).The probiotics were defined as live microbial feed supplements that improve health of man and terrestrial livestock. The gastrointestinal microbiota of fish and shellfish are peculiarly dependent on the external environment, due to the water flow passing through the digestive tract. Most bacterial cells are transient in the gut, with continuous intrusion of microbes coming from water and food. Some commercial products are referred to as probiotics, though they were designed to treat the rearing medium, not to supplement the diet. This extension of the probiotic concept is pertinent when the administered microbes survive in the gastrointestinal tract. Otherwise, more general terms are suggested, like biocontrol when the treatment is antagonistic to pathogens, or bioremediation when water quality is improved. However, the first probiotics tested in fish were commercial preparations devised for land animals. Though some effects were observed with such preparations, the survival of these bacteria was uncertain in aquatic environment. Most attempts to propose probiotics have been undertaken by isolating and selecting strains from aquatic environment. These microbes were Vibrionaceae, pseudomonads, lactic acid bacteria, Bacillus spp. and yeasts. Three main characteristics have been searched in microbes as candidates to improve the health of their host. (1) The antagonism to pathogens was shown in vitro in most cases. (2) The colonization potential of some candidate probionts was also studied. (3) Challenge tests confirmed that some strains could increase the resistance to disease of their host. Many other beneficial effects may be expected from probiotics, e.g., competition with pathogens for nutrients or for adhesion sites, and stimulation of the immune system. The most promising prospects are sketched out, but considerable efforts of research will be necessary to develop the applications to aquaculture.


What are aquatic probiotics?


The concept for aquatic probiotics is a relatively new. When looking at probiotics intended for an aquatic usage it is important to consider certain influencing factors that are fundamentally different from terrestrial based probiotics. Aquatic animals have a much closer relationship with their external environment. There are the big differences between terrestrial and aquatic animals in the level of interaction between the intestinal microbiota and the surrounding environment. On the other hand, potential pathogens are able to maintain themselves in the external environment of the aquatic organisms and proliferate independently of the host (Hansen and Olafsen 1999; Verschuere et al. 2000; Kesarcodi-Watson et al. 2008). The bacterial community composition of the intestinal tract of

aquatic animals is different from that found in terrestrial animals, which the probiotic concept was developed. Man and terrestrial livestock undergo embryonic development within an amnion, whereas the larval forms of most fish and shellfish are released in the external environment at an early ontogenetic stage. These larvae are highly exposed to gastrointestinal microbiota-associated disorders, because they start feeding even though the digestive tract is not yet fully developed (Timmermans 1987), and though the immune system is still incomplete (Vadstein 1997). Thus, probiotic treatments are particularly desirable during the larval stages (Gatesoupe 1999). The resident microbes benefit from a fairly constant habitat in the GI tract of man and terrestrial livestock, whereas most microbes are transient in aquatic animals (Moriarty 1990). These animals are poikilothermic and their associated microbiota may vary with temperature changes. Salinity changes in the rearing environment will also affect the microbiota and marine finfish are obliged to drink constantly to prevent water loss from the body. A consequence of the specificity of aquatic microbiota is that the most efficient probiotics for aquaculture may be different from those of terrestrial species (Gatesoupe 1999; Kesarcodi-Watson et al. 2008). Defining probiotics is a challenge – even more so for aquaculture application. Historically, probiotics were defined according to their expected benefits or improvement to the host’s intestinal balance. Being concerned with humans and terrestrial animals, probiotics were generally Gram-positive obligate or facultative anaerobes, mostly LAB. Based on the intricate relationship an aquatic organism has with the external environment when compared with that of terrestrial animals, the definition of probiotics for aquatic animals was modified at the end of the last century.

Verschuere et al. (2000) defined aquatic probiotics as "Live microorganisms that have a beneficial effect on the host by modifying the microbial community, associated with the host, by ensuring improved use of the feed or enhancing its nutritional value, by enhancing the host response towards disease, or by improving the quality of its ambient environment". This implies a much wider range of microorganisms being used as probiotics for aquaculture animals that for terrestrial animals. The above definition is a more holistic and most appropriately defines probiotics for aquaculture.

Probiotics that currently used in aquaculture industry include a wide range of taxa – from Lactobacillus, Bifidobacterium, Pediococcus, Streptococcus and Carnobacterium spp. to Bacillus, Flavobacterium, Cytophaga, Pseudomonas, Alteromonas, Aeromonas, Enterococcus, Nitrosomonas, Nitrobacter, and Vibrio spp., yeast (Saccharomyces, Debaryomyces) and etc. (Irianto and Austin 2002; Burr et al. 2005; Sahu et al. 2008).

Aquatic probiotics are mainly of two types:

1) Gut probiotics which can be blended with feed and administrated orally to enhance the useful microbial flora of the gut .

2) Water probiotics which can proliferate in water medium and exclude the pathogenic bacteria by consuming all available nutrients. Thus, the pathogenic bacteria are eliminated through starvation (Nageswara and Babu 2006; Sahu et al. 2008).

The first type probiotics are using mainly in finfish aquaculture and the second type in shrimp aquaculture. Commercially available probiotics include pure strains, defined mixture of specific strains, but also consortia of strains and undefined mixtures. Generally, probiotics proposed as biological control agents in fish aquaculture are applied in the feed or as a water additive supplement.


Aquatic probiotics are marketed in two forms:

1) Dry forms: the dry probiotics that come in packets can be given with feed or applied to water. They have many benefits, such as safety, easy using, longer shelf life and etc. (Decamp and Moriarty 2007);

2) Liquid forms: the hatcheries generally use liquid forms which are live and ready to act. These liquid forms are directly added to hatchery tanks or blended with farm feed. The liquid forms can be applied any time of the day in indoor hatchery tanks, while it should be applied either in the morning or in the evening in outdoor tanks. Liquid forms give positive results in lesser time when compared to the dry and spore form bacteria, though they are lower in density (Nageswara and Babu 2006).

There are no reports of any harmful effect for probiotics but it is found that the biological oxygen demand level may temporarily be increased on its application; therefore it is advisable to provide subsurface aeration to expedite the establishment of probiotics organisms. A minimum dissolved oxygen level of 3% is recommended during probiotics treatment. The development of suitable probiotics for aquaculture is not a simple task. It requires empirical and fundamental research, full-scale trials as well as the development of appropriate monitoring tools and production under stringent quality control. A performing mixture of probiotic strains can be designed after evaluating the ability of individual strains to grow in low/high salinity under micro-aerophilic or anaerobic conditions, produce various enzymes, and more importantly, produce a range of inhibitory compounds (Decamp 2004).

  1. Vaccine

A vaccine is any biologically based preparation intended to establish or to improve immunity to a particular disease or group of diseases. Vaccines have been used for many years in humans, terrestrial livestock, and companion animals against a variety of diseases.

Vaccines work by exposing the immune system of an animal to an "antigen"—a piece of a pathogen or the entire pathogen—and then allowing time for the immune system to develop a response and a "memory" to accelerate this response in later infections by the targeted disease-causing organism. Vaccines are normally administered to healthy animals prior to a disease outbreak.

One analogy used for vaccines is that of an insurance policy (Komar et al 2004). A vaccine, if effective, can help prevent a future disaster from being a major economic drain. But vaccines, like insurance, have a premium, or cost. The producer must weigh the cost in materials and labor against the risk and cost of a disease outbreak to determine whether vaccination is warranted. When actual vaccine effectiveness is also unknown, this makes decision-making even more difficult. Consultation with a fish veterinarian or other fish health specialist will be helpful when examining cost vs. benefit of a particular vaccine.

The ideal vaccine:

    1. is safe for the fish, the person(s) vaccinating the fish, and the consumer;

    2. protects against a broad strain or pathogen type and gives 100% protection;

    3. provides long-lasting protection, at least as long as the production cycle;

    4. is easily applied;

    5. is effective in a number of fish species;

    6. is cost effective; and

    7. is readily licensed and registered (Grisez and Tan 2005).


What are the different types of vaccines?

There are many different types of vaccines, and new kinds are continuously under development. Of the types currently in use, the most common are described below.

Bacterins are vaccines comprised of killed, formerly pathogenic bacteria. Bacterins stimulate the antibody-related portion of the immune response (i.e., the humoral immune response).

Live, attenuated vaccines are comprised of live micro-organisms (bacteria, viruses) that have been grown in culture and no longer have the properties that cause significant disease. Live attenuated vaccines will stimulate additional parts of the immune system (i.e., a cell-mediated, as well as a humoral [antibody] response).

Toxoids are vaccines comprised of toxic compounds that have been inactivated, so they no longer cause disease. An example, used in humans, is the tetanus toxoid vaccine.

Subunit vaccines are made from a small portion of a micro-organism (rather than the entire micro-organism) that ideally will stimulate an immune response to the entire organism.

Other types of vaccines in development use even more modern strategies. Examples include recombinant vector vaccines, which combine parts of disease-causing micro-organisms with those of weakened microorganisms, and DNA vaccines. Recombinant vector vaccines allow a weak pathogen to produce antigen. DNA vaccines are composed of a circular portion of genetic material that can, after being incorporated into the animal, produce a particular immune-stimulating portion of a pathogen (i.e., antigen) continuously, thus providing an "internal" source of vaccine material. Other vaccine strategies are also undergoing research and development.


How are vaccines given to fish?

Vaccines are administered to fish in one of three ways: by mouth, by immersion, or by injection. Each has its advantages and disadvantages. The most effective method will depend upon the pathogen and its natural route of infection, the life stage of the fish, production techniques, and other logistical considerations. A specific route of administration or even multiple applications using different methods may be necessary for adequate protection.

Oral vaccination results in direct delivery of antigen via the digestive system of the fish. It is the easiest method logistically because feeding is a normal, ongoing part of the production schedule. Stress on the fish is minimal, and no major changes in production are required. Prior to feeding, vaccine is mixed, top-dressed, or bioencapsulated into the feed. To reduce leaching into the water and/or to provide some protection against breakdown of the vaccine by the fish's digestive processes, a coating agent is often used. For small fish (e.g., 1-5 g or less), bioencapsulation may be a preferred method of oral delivery. Live food (rotifers, brine shrimp) is added to a concentrated vaccine solution, and allowed to take up vaccine. This live food is then fed to fry or small fingerlings. Although oral vaccine is the most preferred method, it conveys relatively short immunity (compared to the other methods) such that additional vaccination may be required. In addition, because of the problems involved with getting the vaccine intact through the intestine and adequately stimulating the immune system, there are few commercial oral vaccines available (Komar et al. 2004).

Immersion vaccination permits immune cells located in the fish's skin and gills to become directly exposed to antigens. These immune cells may then mount a response (e.g., antibody production), thus protecting the fish from future infection. Other types of immune cells in the skin and gills carry antigens internally, where a more systemic response will also develop. Immersion vaccination occurs by dip or by bath. Dips are short, typically 30 seconds, in a high concentration of vaccine. Baths are of longer duration—an hour or more—and in a much lower concentration of vaccine. In practice, dips are logistically more practical for large numbers of small (1- to 5-g) fish. Unfortunately, protection using immersion methods may not last long and a second vaccination may be required (Komar et al. 2004) because smaller, younger fish may have immature immune systems and because this is a more indirect route.

Injection vaccination allows direct delivery of a small volume of antigen into the muscle (intramuscular (IM) injection) or into the body cavity (intracoelomic [ICe= intraperitoneal or IP] injection), allowing for more direct stimulation of a systemic immune response. Injection vaccines normally include an oil-based or water-based compound, known as an adjuvant, that serves to further stimulate the immune system. Injection is effective for many pathogens that cause systemic disease; and protection—6 months to a year—is much longer than by other methods. Every fish in the population is injected, giving more assurance to the producer. Another advantage is that multiple antigens (for different diseases) can be delivered at the same time. However, vaccination by injection is logistically the most demanding of all three methods. Fish must be anesthetized to minimize stress. Injection requires more time, labor, and skilled personnel. The correct needle size is important. The vaccine may incite a more severe reaction if it is injected into the wrong portion of the fish. And finally, smaller-sized fish (under 10 g) may not respond well to this method (Komar et al 2004).


Have vaccines been used in fish?

Vaccines have been used in food fish, in particular the salmon industry, for approximately 30 years, and are believed to be one of the main reasons that salmon production has been so successful. Vaccination of salmon also dropped the industry's use of antibiotics to a mere fraction of its original use (Sommerset et al 2005). In Norway, for example, in 1987, before widespread use of vaccines, approximately 50,000 kg of antibiotics were used. By 1997, when vaccines had become more routine, antibiotic usage had dropped to less than 1000-2000 kg (Sommerset et al. 2005).

  1. Immunostimulants

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—

  1. bacteria and bacterial products,

  2. complex carbohydrates,

  3. vaccines,

  4. immunity enhancing drugs,

  5. nutritional factors,

  6. animal extracts,

  7. cytokines, and

  8. Lectins, plant extracts.

Two main procedures for evaluating the efficiency of an immunostimulants are:

  1. In vivo, eg., protection tests against fish pathogens: and

  2. 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 discussion here.

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:

  1. It should be non-toxic, even at a high dose rate.

  2. It should be non-carcinogenic or have long term side effects.

  3. At therapeutic levels, it should have a short withdrawal period with low tissue residues.

  4. It should stimulate a wide range of non-specific immune responses against bacteria, fungi, virus, protozoa and helminthes.

  5. It should be capable of amplifying primary and secondary immune responses to infectious agents.

  6. Breakdown products of compound concerned should be either inactive or readily biodegradable in the environment.

  7. It should be having defined chemical composition or biological activity.

  8. It should be active by oral route and should be stable both in its native state and after incorporation into food and water.

  9. It should be compatible with arrange of drugs including antibiotics and anthelmintics, and

  10. It should be inexpensive and either tasteless or palatable.



Objectives of immunostimulation:

These are:

  1. Promoting a greater and more effective sustained immune response to those infectious agents producing subclinical disease without risks of toxicity, carcinogenicity or tissue residues.

  2. Hastening the maturation of non-specific and specific immunity in young susceptible animals.

  3. Enhancing the level of duration of specific immune response, both cell mediated and humoral, following vaccination.

  4. Overcoming of immunosuppressive effects of stress and of those infectious agents that damage or interface with the functioning of cells of immune system.

  5. 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

  6. 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:

  1. Enhancement of antibody activity.

  2. Stimulation of polyclonal activation of lymphocytes, and

  3. 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:

  1. enhancement of cell mediated cytotoxicity, lymphokine production and suppressor cell function, and

  2. 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 immersion.

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 Klebsiellapneumoniae 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 healing.

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 serotoxin.

Leaf extract of Ocimum sanctum: Effect of leaf extract Ocimum sanctum on:

  1. the specific and non-specific immune responses and

  2. 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 usingO. 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.


References

Gibson GR, Roberfroid MB (1995). Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics. J. Nutr. 125: 1401-1412.

Mahious AS, Ollevier F (2005). Probiotics and Prebiotics in Aquaculture.1st Regional Workshop on Techniques for Enrichment of Live Food for Use in Larviculture-2005, AAARC, Urmia, Iran. p. 67.

Fooks LJ, Fuller R, Gibson GR (1999). Prebiotics, probiotics and human gut microbiology. Int. Dairy J. 9: 53-61.

Gibson GR, Probert HM, Van Loo J, Rastall RA, Roberfroid MB (2004). Dietary modulation of the human colonic microbiota: Updating the concept of prebiotics. Nutr. Res. Rev. 17: 259-275.

Breves G, Sztkuti L, Schr˛der B (2001). Effects on oligosaccharides on functional parameters of the intestinal tract of growing pigs. Deutsche Tierarztliche Wochenschrifte 108: 246-248.

Bongers A, van den Huevel EGHM (2003). Prebiotics and the bioavailability of mineral and trace elements. Food Rev. Int. 19: 397-422.

Parker, R.B., 1974. Probiotics. The other half of the antibiotic story. Anim. Nutr. Health

29: 4-8.

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