Aquaculture is the most rapidly developing food industry. Many different fish species are farmed worldwide, but about 65% are extensively farmed carp. The remainder are high value species, such as salmon, farmed on an industrial scale. As a result, the global fish yield from aquaculture now exceeds that of wild-caught fisheries. In addition, wild caught fisheries are reaching their maximum output, and a quarter of wild fish populations are overfished or seriously depleted. As a result of this intensification, stocking densities in commercial aquaculture have risen. This has caused increased stress, and greatly increased the risk of infectious disease outbreaks in farmed fish. Infectious diseases are therefore a major issue for the industry and as a result, Intensive bacterial and viral vaccination is essential for its commercial success. Vaccine use has enabled the intensive industry to significantly reduce antibiotic consumption. In general, industrial scale vaccination is mainly limited to larger, high-value fish such as salmon and trout, and seeks to get the fish to market weight with only a single cycle of vaccination. As a result, there is a reliance on early vaccination followed by boosters to provide long-lasting disease protection. Killed bacterial vaccines predominate in the fish industry. It has proven to be much more difficult to produce effective viral vaccines, whereas the use of modified live vaccines is discouraged because of potential environmental risks. Vaccines are therefore used in 77 species of fish against more than 22 different bacterial diseases and 6 viral diseases. A major consideration concerns the methods used to administer vaccines to fish. This includes not only their aquatic environment, but also the great variations in size and feeding behavior as fish grow. The first licensed vaccines against Yersinia ruckeri and Vibrio anguillarum for fish in the United States were introduced into commercial aquaculture in the early 1980s. Thereafter many killed bacterial vaccines have been used routinely. About 30 licensed fish vaccines are available worldwide. These differ between countries and some are specific for a single fish species. It should also be noted that, as in all animal vaccines, they must be cost-effective. Thus there are enormous differences in vaccination practices between the large commercial fisheries raising Atlantic salmon and the small-scale carp-production activities in villages in East Asia. Bony fish (teleosts) have a complete set of lymphoid organs except for a bone marrow, and they can mount both innate and adaptive immune responses. Their lymphoid organs are very different from those in mammals. For example, their thymus may involute in response to hormones or season. Age involution is inconsistent, and a thymus may be found in old fish. Fish kidneys differentiate into two sections. The opisthonephros or posterior kidney is similar to the mammalian kidney. In contrast, the pronephros or anterior kidney is a lymphoid organ containing antibody-forming cells and phagocytes. Its function is analogous to mammalian bone marrow and lymph nodes. Fish have a spleen with a structure and function similar to that in mammals. Aggregates of lymphocytes are prominent in the fish intestinal tract. Fish also have clusters of macrophages containing melanin and hemosiderin. These melanomacrophage centers are found in the spleen, liver, and kidney. Antigens may persist in these centers for long periods, and they appear to be precursors of the germinal centers found in more evolved vertebrates. Teleosts also have dendritic-like cells that can present antigens to T cells. Fish lymphocytes resemble those of mammals. B cells can be found in the thymus, anterior kidney, spleen, Leydig organ, and blood, and their surface immunoglobulins act as antigen receptors. These B cells can mature into plasma cells. Unlike mammalian B cells, however, teleost B cells can phagocytose particles, generate phagolysosomes, and kill ingested microbes. Both helper and cytotoxic T cells can be detected in fish. Fish antibody responses are characterized by the predominance of IgM produced by plasma-like cells in the anterior kidney. In the presence of complement, fish antibodies can lyse target cells, but there is no evidence that they can act as opsonins. The blood vessel walls of fish are permeable to immunoglobulin (Ig)M. As a result, antibodies are found in most tissue fluids including plasma, lymph, and skin mucus. Fish do not produce IgA, but they secrete a mucosal IgM together with IgD. One significant difference between fish and other vertebrates is that their antibodies do not undergo class switching or affinity maturation. IgT is the major mucosal and skin immunoglobulin in teleosts. Not all antigens are effective immunogens in fish. Soluble protein antigens are poorly immunogenic, in contrast to particulate antigens such as bacteria that are very potent. Environmental temperatures have a significant influence on vaccine responses. Antibody production in vaccinated Atlantic salmon is significantly less in fish held at 2°C than in those held at 10°C. Social interactions can also influence their immune response; fish kept at a high population density are immunosuppressed, a matter of some concern in commercial aquaculture. Administration of vaccines to large numbers of fish presents challenges. One major issue is the vulnerability to infection of very small larval or fry stages before immune system development and before they are large enough to vaccinate. Three routes are available for vaccination of larger fish: injection, immersion, and oral. Each has advantages and disadvantages. The usual way to vaccinate fish on an industrial scale is by intraperitoneal or intramuscular injection (Fig. 21.1). The effectiveness of vaccines is greatest if injected, but the process does place significant stress on the fish. In addition, injected vaccines can only be used on larger fish. The best results are obtained with vaccines incorporating oil-emulsion based adjuvants such as mineral oil with an emulsifier or a vegetable/animal oil with pristane or squalene. When vaccinating very large numbers, the fish are carried through pipes from the rearing tanks to an anesthetic bath. Once lightly anesthetized, the fish are removed from the bath, placed on a table, and injected by the vaccination team using repeating injection guns connected to a vaccine bag or bottle. Each fish has to be handled individually and injected by hand. The fish is held ventral side up with its head facing away from the operator. The vaccine is injected into the abdominal area of each anesthetized fish. The needle is inserted about 5mm. Depending on the vaccine, 0.05 to 0.2mL of fluid is injected. The recommended volume is 0.1 mL per fish weighing a minimum of 39 g. Using automatic injection guns, four skilled operators can vaccinate 5000 salmon per hour. However high labor costs have led to the development of automated vaccination machines that can vaccinate up to 20,000 fish per hour (Fig. 21.2). Intraperitoneal vaccines are generally used to deliver water-in-oil emulsion vaccines whereas intramuscular injection is employed for DNA vaccines. Before vaccination fish must be fasted for 12 to 24 hours, the fish tanks made ready, and the water aerated. This reduces stress and anesthesia complications. As with all vaccines, only healthy fish should be vaccinated and it is essential not to overstock them. The most commonly used anesthetic in Europe and the United States is MS-222 (also called Tricaine methanesulfonate or Tricane-S). This is a sodium channel blocker with a wide safety margin approved for use in food fish. It does not affect their respiratory system and fish recover rapidly. The dose ranges from 20 to 50 mg/L depending on the species. MS-222 is light sensitive, and should be stored appropriately and prepared fresh each time. Although highly soluble, it will acidify the tank water so it should be buffered with sodium bicarbonate. This may not be necessary for seawater. Fish should be vaccinated at water temperatures from 1°C to 18°C and preferably below 15°C. The vaccination equipment should be disinfected before use. The vaccine should be left to slowly reach 15°C to 20°C by keeping it at room temperature and should be well shaken before use. To reduce the risk of adverse reactions, it is important to deposit the entire dose in the abdominal cavity. The injection needle used should have appropriate diameter, and length to penetrate the abdominal wall by 1 to 2 mm. The entire needle should be inserted into the midline about 1 to 1.5 pelvic fin lengths anterior to the base of the pelvic fin (Fig. 21.3). When using automated methods, anesthetized fish are wedged into an enclosed space and auto-injected. This may be less satisfactory than the use of hand injectors because the number of injection site lesions is increased. Inactivated vaccines must be administered by injection to induce protective immunity, but for some viral diseases, this may not be practical. Thus injection is not appropriate for small fish and so cannot be performed very early in life. This means that there may be a window of disease susceptibility as the fish are growing before reaching a size suitable for injection. Vaccine injection also needs complex machinery and a skilled staff so that the cost of labor is significant. Depending upon the adjuvant employed, complications such as postvaccinal fungal diseases, or severe local reactions with tissue damage may occur. For this reason fish farmers are reluctant to give fish more than one injection in the production cycle. There is also a desire to incorporate as many vaccines as possible into that injection. On the other hand, injection gives long lasting immunity, and each fish is assured of getting the correct dose of vaccine. Given the cost, complexity, and risks of injection, fish farmers have turned to immersion vaccination where fish are placed in a dip or bath containing the vaccine antigen. They remain for a suitable time period while the antigen is absorbed through their skin, mucosal surfaces, and gills. In dip vaccination, small fish are immersed for 30 seconds in a highly concentrated vaccine solution (1/10 dilution of the vaccine). In bath vaccination, larger fish are exposed for a longer period (∼30 min) in a dilute vaccine solution (1/500 dilution). Dip vaccination is more widely used because it lends itself to the mass vaccination of small fish and uses a relatively small volume of vaccine solution. For example, salmonid fish as small as 2g can be vaccinated by immersion. Because the fish are not individually handled they suffer much less stress and mortality, and labor costs are much lower. Dip vaccination can also be very rapid, with up to 100 kg of fish vaccinated per liter of vaccine. It is the preferred method of vaccinating small fish or fry under 5g. Dip vaccination is impractical and cost prohibitive for larger fish. Bath vaccination, in contrast, is less stressful on the fish and less labor intensive. Large-scale bath vaccination is used, for example, in sea bass in Europe. In this method, large groups of fish are cut off from the rest of the tank. They are sedated with a low dose of anesthetic, exposed to the vaccine while air or oxygen is pumped into the tank to prevent suffocation. However, a large volume of vaccine solution is required, which makes it expensive for the immune response induced by this method provides less protection and a shorter duration of immunity than does injection. It is somewhat effective in inducing mucosal immunity. Oral vaccination is the preferred route when fish welfare and labor costs are considered. Vaccines can be delivered at any age, stress is minimized, and the price is right. Because of the relatively low cost, oral vaccines can be delivered multiple times. However, oral vaccination requires a very large amount of antigen and the fish need to be feeding. Additionally, like the immersion techniques, protection using these inactivated products is relatively poor and of relatively short duration. Oral vaccines generally contain heat- or formalin-killed organisms. The vaccines can be mixed with the feed or coated on the surface of the feed pellets. The major problem affecting oral vaccines is their lack of stability. The vaccine antigens have to survive the food making process and they must be stable in water and persist within the fish gastrointestinal tract. Another problem is that the dose of vaccine ingested is uncertain. Although oral vaccines are not adjuvanted they do need to be protected against digestion and dilution in water. There are three ways of doing this. The finished feed can be “top-dressed” with powdered vaccine by adding adhesive substances such as an edible oil or gelatin. A second way is simply to spray the feed with a vaccine solution. The third way is to mix the vaccine in the feed during the feed production process. The first two methods, although simple, may result in an uneven distribution of antigen in the feed. These antigens will also be directly exposed to stomach acidity and thus may be degraded. On the other hand, mixing the antigen in the feed results in uniform distribution of antigen. However, feed is often produced by high temperature extrusion that may destroy antigens. Thus the antigen must be added at a later stage in food preparation. Vaccines may also be bioencapsulated. Once encapsulated they can then be mixed in the food. Two commercial microencapsulation processes are also used. This may involve either an “Antigen-protecting vehicle” (APV) (Vibrio anguillarum, Yersinia ruckeri, and infectious pancreatic necrosis (IPN); MSD Animal Health), or a patented MicroMatrix delivery system (Piscinickettsia salmonis, ISAV and IPNV, Centrovet). These processes are designed to protect antigens against gastric digestion and increase mucosal uptake. APV prevents digestion in the stomach and ensures that viral antigens are delivered to the hindgut where they are absorbed. Other approaches may include encapsulating antigens in liposomes or alginate beads. Given the advantages and disadvantages of the different routes of vaccination described earlier, there is a clear pattern of vaccine usage designed to protect fish throughout their life. Depending on the species and production cycle, fish farmers commonly start with a dip vaccine, followed by a dip or oral boost, and finish with an intraperitoneal injection. Revaccination is not usually employed after this injection, although oral boosting against piscirickettsiosis is used in Chile. Increasing water temperature will improve the response to vaccines and it is possible to use this to advantage. For example, vaccination in the fall leads to the immune system delaying its response until the following spring when the water temperature rises. The onset of immunity is faster in warm-water species than in cold-water species. For example, in sea bass held at 22°C antibodies appear about one week after vaccination. On the other hand, in salmon held at 10°C, antibodies only appear by four to six weeks. Fish develop antibodies against a wide range of bacterial pathogens, and killed bacterial vaccines against gram-negative bacteria give very good protection. Oil-based adjuvants are widely employed in these injectable vaccines, although as described earlier they may produce significant injection site reactions. They are both efficacious and safe when administered correctly. Listonella anguillarum (Vibrio anguillarum), and Vibrio ordalli, cause classical vibriosis, the most serious bacterial fish disease and one that causes severe economic loss. It presents as a septicemia that affects Atlantic and Pacific salmon, rainbow trout, sea bass, sea bream, turbot, cod, and eel. It is found worldwide but does not occur in very cold seawater or in freshwater aquaculture. There are at least ten different serotypes of L. anguillarum of which three are most significant: O1, O2a, and O2b. O1 and O2a serotypes affect salmonids and O2b affects cold-water species such as cod and halibut. As a result the salmonid vaccines cannot be used in these marine species. It is important to use the correct serotype in the bacterin. Both injectable and immersion vaccines are available. Larvae and small juveniles need to be vaccinated by immersion. Vibrio anguillarum-ordalii bacterin (Vibrogen 2, [Elanco Aqua Health]) is administered using the same process as other dips for a 30-second exposure. The injectable vaccines are usually polyvalent adjuvanted bacterins and work well. The cause of cold-water vibriosis is Aliivibrio (Vibrio) salmonicida. The organism is most virulent between 3°C and 10°C. It is found only in seawater species. This septicemic disease was brought under control by vaccination beginning in the 1980s, for many years, but it has now reappeared. It is mainly a problem in Norwegian aquaculture, hence most Atlantic salmon and rainbow trout in Norway are vaccinated. Killed bacterins are available. They are administered by immersion or injection and appear to be very effective. Aeromonas salmonicida is the causal agent of Furunculosis, another major disease of salmonid fish. Species such as carp, cod, or flounder may also be affected. This may present as sudden death, but salmon may develop “boils” involving skin or muscle. Both immersion and injectable bacterins are available, although oil adjuvanted injectable vaccines seem to be preferred. The injected bacterin is injected intraperitoneally to anesthetized salmonids. Moritella viscosa is the main causal agent of winter ulcer that affects Atlantic salmon and rainbow trout. The fish develop superficial ulcers that grow and penetrate the skin. It is economically devastating because of death losses and quality downgrading. Formalin inactivated bacterins are available. They are usually included in polyvalent vaccines so the coverage is high. Yersinia ruckeri is the cause of enteric redmouth (ERM) disease. It mainly occurs in cultured salmonids such as rainbow trout. It affects very small fish, and as in so many fish diseases is attributed to stress. Trout are initially vaccinated by immersion in the hatchery. However, this only protects them for about nine months. They must therefore be revaccinated orally. Two oral vaccinations should provide sufficient protection and cause minimal stress to the fish. Photobacterium damselae subsp. piscicida (Pasteurella piscicida) causes a septicemia called pseudotuberculosis. It has caused high mortality in Mediterranean aquaculture. It affects many species of marine fish. Bacterins are available for immersion or injection. Two bath immersions are used when the fish are 45 to 50 days of age. The vaccine only induces short-term immunity so this may be boosted orally or by injection Multiple species of vibrio cause this hemorrhagic skin disease. The most important are Vibrio alginolyticus, Vibrio parahaemolyticus, and Vibrio vulnificus. V. vulnificus is an important human pathogen, causing lethal wound infections. Mixed bacterins are available. Generally fish are first vaccinated by injection and then boosted by immersion. Edwardsiella ictaluri is a gram-negative bacterium that causes enteric septicemia of channel catfish, the most serious disease affecting the catfish industry in the United States. A mortality of up to 37% has been associated with E. ictaluri infection. The disease is associated with water temperatures over 22°C. Vaccines have not been widely employed because of the extensive methods of fish farming. Killed bacterins are of low efficacy despite inducing antibodies because this organism is a facultative intracellular organism and cell-mediated responses are probably more important. As a result, live attenuated products delivered by immersion may work better. An avirulent live attenuated vaccine (Aquavac-Esc, Merck) is used in healthy catfish by immersion. It is provided in frozen vials where each vial is sufficient to vaccinate 7.5 lbs. (3.4kg) of catfish in 5gal (20L) of water. This vaccine is efficacious in channel catfish fry as early as 7 to 30 days post hatching. A related bacterium, Edwardsiella tarda, causes gangrene and septicemia in other freshwater fish such as channel catfish, eels, and flounder, but there are no commercial vaccines available. It can affect humans. Flavobacterium columnare causes a significant skin disease in many different freshwater fish, especially trout, catfish, and bass. An avirulent live culture is used to vaccinate healthy catfish and largemouth bass by immersion. A killed immersion vaccine is also available. Renibacterium salmoninarum is the cause of bacterial kidney disease. An attenuated live vaccine has been licensed that relies on cross-reactivity between this organism and Arthrobacter spp. It is administered by immersion or injected intraperitoneally Piscirickettsia salmonis is the causal agent of salmon rickettsial septicemia, a very serious disease in Chile where it may cause mortality exceeding 90% in farmed Coho salmon. Inactivated bacterins are available but of low efficacy. This lack of effectiveness may be attributed to coinfection with sea lice. A live attenuated vaccine is also available. Streptococcus agalactiae and Streptococcus iniae cause significant mortality in Nile tilapia, one of the most cultivated fish in the world after carp and salmon. These fish are farmed intensively worldwide, but the consequent increase in stocking densities has resulted in stress-induced immunosuppression, leading to an upsurge in lethal streptococcal infections. Streptococcosis is a bacterial disease that affects warm water fish in either salt or freshwater environments, typically in tropical regions. Clinical signs include septicemia, anorexia, hemorrhages, corneal opacity, and exophthalmos. Fish may also develop bloody abscesses around the mouth. High stocking densities, poor water conditions, and high temperatures are the most favorable conditions for streptococcal outbreaks. Tilapia streptococcosis affects fish from as small as 5 grams, and is present throughout the entire tilapia growth cycle. Intraperitoneal oil-adjuvanted vaccines are widely used and stimulate effective protection. Immersion, oral, and spray vaccines have also been investigated with limited success. Lactococcosis caused by Lactococcus garvieae, affects saltwater fish in East Asia, especially rainbow trout, Japanese yellowtail, and gray mullet. A bacterin is available that is administered intraperitoneally. Most fish viral vaccines are inactivated products or recombinant subunits delivered by intraperitoneal injection. The nature of commercial aquaculture is such that administration of live viral vaccines will effectively result in contamination of their aqueous environment. The risks of uncontrolled spread, ecological damage, and reversion to virulence are not insignificant. As a result, few trials have been made with live vaccines in commercial aquaculture. Because of their economic value, most antiviral vaccines have been directed against salmonid pathogens. Infectious pancreatic necrosis virus (IPNV) is a birnavirus mainly affecting young trout and salmon in Europe and North America. It causes a sudden mortality with abdominal swelling and anorexia. Numerous vaccines are available against IPNV. They are either subunit vaccines or inactivated products. The subunit vaccines contain the major viral antigen VP2 expressed in Escherichia coli. They may be delivered orally or by intraperitoneal injection. The adjuvanted vaccine is injected into pre-smolts. A combined Aeromonas salmonicida and IPNV oil-adjuvanted intraperitoneal vaccine is also available. Protection against IPNV has been demonstrated to last for up to 2.5 months. Infectious salmon anemia virus (ISAV) is an orthomyxovirus that affects Atlantic salmon because fish erythrocytes are nucleated they can sustain viral growth. Fish may develop pale gills but more often die suddenly so that death rates may reach 100%. Some trout may act as healthy carriers and sea lice can carry the virus. It occurs in Europe and the Americas. Subunit and inactivated vaccines are available. The subunit vaccine contains the ISAV recombinant hemagglutinin esterase gene and is given orally. There are multiple inactivated monovalent or combined vaccines. For example there is an ISAV, Aeromonas salmonicida-Vibrio anguillarum-ordalii-salmonicida bacterin available. All inactivated ISAV vaccines are administered intraperitoneally. Infectious hematopoietic necrosis (IHN) is caused by a rhabdovirus. IHN affects salmonid fish on the Pacific coast of Canada and the United States where it is endemic. It is also present in Japan, Korea, and Europe. It primarily impacts farms rearing fry or juvenile rainbow trout with mortality up to 90%. Clinical signs include abdominal distention, anemia, and hemorrhage from the mouth, gills and anus, and also the yolk sac in fry. As its name implies, kidney necrosis occurs. The disease is especially interesting because the first DNA-plasmid vaccine was licensed against this disease. Studies demonstrated that only the viral glycoprotein (G) is capable of inducing neutralizing antibodies. Administered by a single intramuscular injection, the vaccine consists of a plasmid containing a cytomegalovirus promoter that drives expression of the IHN G protein. The use of a promoter from a human pathogen, cytomegalovirus, makes this vaccine “unsafe” in some countries. Encouraging results have been obtained by incorporating the vaccine into alginate microspheres and feeding it. Salmonid alphavirus is the cause of salmon pancreas disease in Europe. It is a positive-stranded RNA alphavirus of the Togaviridae family. Mortality may be low but survivors fail to grow and may die months later. An inactivated vaccine given intraperitoneally is efficacious and significantly reduces viral shedding. A DNA-plasmid vaccine has been licensed in Europe for the prevention of this disease, caused by alphavirus subtype 3 (Clynav, Elanco). This is a highly infectious disease primarily affecting trout and flounder. It is caused by a weakly immunogenic rhabdovirus. As a result, it has been difficult to develop an effective vaccine. Several experimental vaccines have been developed including inactivated, modified live, recombinant protein, and DNA vaccines, but none have been commercialized as yet. Spring viremia of carp (SVC) is a swim bladder infection caused by a rhabdovirus (Rhabdovirus carpio). Signs are similar to the other fish viral diseases including abdominal swelling, pale gills, and hemorrhage. Despite its name it affects a diverse range of cultured fish species including catfish, and trout in addition to carp. Subunit and modified live vaccines are available. The subunit vaccine is expressed as a recombinant glycoprotein in a baculovirus expression system. It is given intraperitoneally. The modified live vaccine is given orally. Cyprinid herpesvirus 3 is usually found in common carp in addition to its ornamental varieties such as koi. It causes gill mottling, pale patches on the skin, and vesiculation. Mortality may reach 100%. Death may occur within 24 to 48 hours. As with the other herpesviruses, infected individuals act as healthy carriers. A modified live virus vaccine based on an attenuated carp interstitial nephritis and gill necrosis virus is available. Fish are immersed for 45 to 60 minutes. Fish may be revaccinated before stress or exposure. Because the vaccine container contains live virus, once the fish are vaccinated, the container must be sterilized by burning or immersion in bleach. Viral nervous necrosis caused by a betanodovirus results in viral encephalopathy, and retinopathy and is the most important fish disease in warm waters such as the Mediterranean area. It affects many different species but is especially important in sea bass. An inactivated mineral oil-adjuvanted vaccine is available. It is given by intraperitoneal injection in a very low dose, so as a result it can be given to fish over 12 g. Immunity lasts for a year. Ichthyophthirius multifiliis, is a ciliated protozoan that causes “ich” or “white spot disease.” It is difficult to control by conventional methods. Patents have been awarded for an inactivated oral vaccine but it is not yet commercially available. Local injection site reactions remain an issue in aquaculture. Intraperitoneal inoculation may lead to local or diffuse peritonitis with adhesions. Multiple granulomas may also develop. The lesions contain macrophages, fibroblasts, lymphocytes, and melanomacrophages. More importantly, affected fish show reduced feed conversion and growth. Lesions in the fish result in increased condemnation and slowing of processing. Intraperitoneal oil-adjuvanted vaccines appear to induce autoimmunity in vaccinated fish. The fish produce multiple autoantibodies, and develop immune-complex glomerulonephritis, liver thrombosis, and spinal deformities. Both polyclonal IgM and antibodies to salmon red blood cells are elevated in vaccinated fish. It is possible that these antibodies are generated within the vaccine-induced granulomas. Because of their high individual value, salmon are routinely vaccinated with water-in-oil adjuvanted vaccines given by injection. One commonly used vaccine is a combination product directed against furunculosis, cold-water vibriosis, winter ulcer, infectious pancreatic necrosis, and infectious salmon anemia. However there are significant differences in vaccine use in different countries based on perceived and actual threats. For example, IHN is a major cause for concern in Western Canada and a DNA vaccine is available to prevent it. Rainbow trout vaccinations differ according to whether they are raised in seawater or freshwater. Large seawater trout are usually vaccinated by injection, whereas smaller freshwater fish tend to receive oral or immersion vaccines. The predominant vaccines employed in seawater trout include those against furunculosis, vibriosis, and winter ulcer. Freshwater trout in contrast suffer predominantly from enteric redmouth disease (yersiniosis), vibriosis (Listonella anguillarum), and flavobacteriosis (Flavobacterium columnare). Cod raised in Norway are generally vaccinated against vibriosis and furunculosis. Sea bass and sea bream raised in Mediterranean countries suffer from vibriosis and pasteurellosis, and may receive a combination vaccine against both. Catfish are also raised worldwide. In the United States channel catfish predominate. Two attenuated live vaccines are available for use in this species against Edwardsiella ictaluri and F. columnare. Tilapia are one of the major fish species raised in aquaculture worldwide. Their major disease problem is Streptococcosis caused by S. agalactiae. Although vaccines are available, the low value of individual fish makes vaccination not cost-effective in many countries.
Fish vaccines
Fish immunity
Adaptive immunity
Methods of vaccination
Injection
Immersion vaccination
Oral vaccination
Vaccination process
Antibacterial vaccines
Vibriosis
Cold-water vibriosis
Furunculosis
Winter ulcer
Yersiniosis
Pasteurellosis
Warm water vibriosis
Edwardsiellosis
Flavobacteriosis
Bacterial kidney disease
Piscirickettsiosis
Other bacterial vaccines
Antiviral vaccines
Infectious pancreatic necrosis
Infectious salmon anemia
Infectious hematopoietic necrosis virus
Salmon pancreas disease
Viral hemorrhagic septicemia
Spring viremia of carp
Koi herpesvirus disease
Viral nervous necrosis
Antiprotozoan vaccine
Adverse events
Species differences
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