fish Vaccination Present status and future challenges

Presented by- Manish kumar I.D.No.- 40024

INTRODUCTON Fisheries will soon reach the maximum capacity in global food

production. Consequently, food from aquaculture will be more important for future food security.

The intensive farming of fin fishes and shellfishes has led to an imbalance of optimal culture conditions, which shows increased susceptibility to infectious disease.

Under these conditions, the prevalence and spread of infectious diseases will unavoidably increase due to higher infection pressure and deterioration of environmental conditions, so good husbandry practices and health management must be emphasized.

Use of antibiotics has attracted lot of criticism due to the issues like antibiotic residues, bacterial drug resistance and toxicity.

In this present scenario, vaccination would be the best alternative to

combat bacterial and viral disease for the sustainable aquaculture.

The first report on fish vaccination was done by David C. B. Duff

and he is regarded as "Father of fish vaccination”.

The vaccines against Fish infectious bacterial diseases were

developed in 1970s, It is commercialized in 1980s.

Later due to the reduced environmental impact and improved food

quality obtained by minimizing antibiotic use in addition, animal

welfare has been improved by the implementation of vaccination.

Definition

A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms the microbe. The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters in future.

Concept of vaccination "Prevention is better than cure”

• Vaccination is an easy, effective and preventive method of protecting fish from diseases. Vaccination is a process by which a protective immune response is induced in an animal by administration of vaccines.

• Once fish stimulated by a vaccine, the antibody-producing cells, called B lymphocytes, remain sensitized and ready to respond to the agent should it ever gain entry to the body.

Mechanism of a vaccine action

TYPES OF VACCINESOn the basis of inducing agent and preparation method Vaccines are can be

classified as-

•Whole-Organism Vaccines Killed Attenuated

• Purified Macromolecules as Vaccines Toxoids Subunit vaccines Conjugate vaccine

• Recombinant vaccine

• DNA vaccine

Whole-Organism Vaccines

Killed or Inactivated: these vaccines contains killed, but previously virulent, micro-organisms that have been destroyed with chemicals, heat, radioactivity or antibiotics.

Infective virus

Empty virus-like particle

Effective, but not Infective

Attenuated: these vaccines contains live, attenuated microorganisms. Many of these are live microorganisms that have been cultivated under conditions that disable their virulent properties or which use closely related but less dangerous organisms to produce a broad immune response.

example • A vaccine for Koi Herpes Virus (KHV) based on attenuated Carp, Interstitial Nephritis and Gill Necrosis Virus .

Inactivated exotoxins or Toxoid Toxoids are vaccines which consist of exotoxins that have been inactivated, either by heat or chemicals. These vaccines are intended to build immunity against the toxins.

Subunit 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.

Example: IPN-vaccine for salmonid fish

Conjugate vaccine Certain bacteria have polysaccharide outer coats that are

poorly immunogenic. By linking these outer coats to proteins, the immune system can be led to recognize the polysaccharide.

RECOMBINANT VACCINES

o Recombinant vaccines are produced by using biotechnology.o Identfy and isolate specific gene from bacteria or virus.o Gene is inserted into plasmid DNA and ligated.This engineered plasmid transformed into another Bacterium.o Allow the bacterial culture to grow and produce the antigenic protein.o The vaccine is purified protein recovered from bacteria or virus.

DNA VaccineWhen the genes for a microbe’s antigens are introduced into the body, some cells will take up that DNA. The DNA then instructs those cells to make the antigen molecules. The cells secrete the antigens and display them on their surfaces. In other words, the body’s own cells become vaccine-making factories, creating the antigens necessary to stimulate the immune system.

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Development of Fish Vaccines

Disease InformationAetiology of Disease

Characterization of Isolates

Definition of Disease

Vaccine Development

Vaccine Production

Lab Vaccination Tests

Pre-Licensing StudiesLicensing

Marketing PreparationPerformance monitoring

Normally 5 – 8 years in R&D

Epidemiology and disease investigation

Laboratory phase

Field and licensing phase

Steps in vaccine production

GROWING THE MICRO- ORGANISMS

ISOLATION & PURIFICATION OF MICROORGANISM

INACTIVATION OF ORGANISM

FORMULATION OF VACCINE

QUALITY CONTROL AND LOT RELEASE

19

virus(production

seed)

Cell culture Harvest Bulk Purification

FormulationFillingLabelingPackaging

Add

Inoculation

cell

Adjuvant Stabilizer

Bulking agent

Preservative

Inspection

centrifugation

filtering

SELECTING THE STRAINS FOR VACCINE PRODUCTION

• The Seed(Strain) -– Manufacturing begins with small amounts of a specific bacteria or virus called as

seed.

GROWING THE MICROORGANISMS

• GROWING BACTERIAMethods used are :– BATCH CULTURE– CONTINUOUS CULTURE

• GROWING VIRUSES– Methods used are :

• CELL (TISSUE) CULTURES• BIRD EMBRYOS• LIVE ANIMAL INOCULATION

Isolation & Purification of microorganism• Product isolation is the removal of those components whose properties vary markedly

from that of the desired product.

• Purification selectively separates and retains the desired product at the highest purity as per its pre-determined specification.(Remove unwanted compounds).

Centrifugation Differential Centrifugation – Density gradient Centrifugation –

Chromatography column chromatography

Ion exchange chromatography:-

Affinity chromatography :-

Filtration Ultra filtration:-

Inactivation of microorganism Virus inactivation involves dismantling a virus’s ability to infect cells

without actually eliminating the virus.

1- By attacking the viral envelope or capsid and destroying its ability to infect or interact with cells.

2- By disrupting the viral DNA or RNA and preventing replication.

Methods are-• Solvent/detergent (S/D) inactivation• Pasteurization• Acidic pH inactivation(Low pH Treatment) • Ultraviolet (UV) inactivation

QUALITY CONTROL AND LOT RELEASE

Prior to release the manufacturer must test-

PURITY, SAFETY, AND POTENCY TESTS-

VIRULENCE TESTS – All live vaccines should be tested for virulence

ASSESSING RISK TO THE ENVIRONMENT –

CONSISTENCY OF PRODUCTION –

STABILITY TESTS

• LABELLING• MARKETTING• PERFORMANCE MONITORING

VACCINE APPLICATION METHODS

Vaccine delivery system

1.    Injection delivery system.2.    Immersion delivery system.3.    Oral delivery system.

Injection vaccination

• Injection delivery system is an effective way of inducing antibody response in fish. The injection may be intraperitoneal or intramuscular.

• Injection is in general superior to any other vaccine application method because it is directly incorporate vaccine in the body.But main disadvantage is it may cause stress and inflammatory reactions.

Immersion vaccination

(a) Dip vaccination (b) Bath vaccination • In dip vaccination, fish are immersed for a short duration, usually 30-60 sec, in

a highly concentrated vaccine solution.• In bath vaccination, fish are exposed for a longer time, usually one to several

hrs, in a lower concentration of antigen.• Immersion vaccination is widely used for fry. It is an effective method that

results in relatively good protection for a significant period of time.

Oral vaccination

• In oral vaccination, the vaccine is either mixed with the feed, coated on top of the feed (top dressed) or bio-encapsulated .

• Bio-encapsulation is used where fish or shrimp fry are to be vaccinated. In this case, live feed such as Artemia nauplii, copepods or rotifers are incubated in a vaccine suspension and then fed to the fry.

• Since these live organisms are non-selective filter feeders, they will accumulate the antigen in their digestive tract and, as such, transform themselves into living microcapsules .

• Recently biofilm of bacterial pathogen has been evolved successfully for oral vaccination of fish with high antibody tire and protection. The glycocalyx of biofilm helps to resist the vaccine destruction in the foregut favouring better antigen delivery to immune responsive sites in the hind gut.

• Oral vaccination has the advantage in that it is easy to administer and causes no stress to the fish.

Current status of fish vaccine developed

VACCINES SPECIES DISEASEAeromonas salmonicida Bacterin Atlantic salmon Furunculosis

Vibrio anguillarum. V. Ordalii Bacterin Rainbow trout Vibriosis,

Yersinia ruckeri Bacterin Salmonids Yersiniosis (enteric red-mouth disease)

Vibrio salmonicida Bacterin Salmonids VibriosisVibrio anguillarum-salmonicida Bacterin Salmonids Vibriosis

Aeromonas salmonicida Bacterin Salmonids Furunculosis

Edwardsiella ictaluri Bacterin Catfish Enteric septicaemia

Spring viraemia of carp virus Common carp Spring viraemia of carp

Koi herpes virus (KHV) Koi carp Koi herpes virus (KHV) disease

Biofilm and free-cell vaccines of Aeromonas hydrophila

Indian major carps Dropsy

Streptococcus agalactiae vaccine Tilapia 

Streptococcosis

Betanodavirus

 

Grouper Betanodavirus disease

Vibriosis• within the genus Vibrio, the species causing the most

economically serious diseases in marine culture are Vibrio anguillarum, V.ordalii, V.salmonicida and V.vulnificus.

• Number of commercial Vibrio anguillarum vaccines have been developed for use mainly by injection.

Winter ulcer:-

Winter Ulcer is a disease affecting sea-farmed atlantic salmon.

Today Moritella viscosa has been incorporated in the Oil-based mutivalent vaccines employed routienly in the salmon industry of the affected countries.

Pasteurellosis-Pasteurellosis currently described also as photobacteriods, is caused by the halophilic bacterium Photobacterium demselae.

Which causes economic losses in the marine culture of yellotail(Seriola quinquerdiata) in Japan.

In recent year, several commercial vaccines against P.damselae have been made available on the market, their efficacy is dependent on fish species, fish size, vaccine formulation.

Furunculosis:-

o Aeromonas salmlonicida is the causative agent which causes economically devastating losses in cultivated salmonids in fresh water and marine waters.

o Many furunculosis bacterins have been developed and commercialized since 1980 to be used in salmonids by injection, immersion or the oral route.

Yersiniosis:-

o Yersinia ruckeri is the causal agent of yersiniosis or enteric red mouth (ERM) disease.

o commercial ERM vaccines have been extensively used for decades. the formalin-killed whole-cell vaccine continues to be highly effective whether administered by immersion, spray, injection or oral routes.

.

Enteric septicaemia of cat fish, ESC (Edwardsiella ictaluri)

Edwardsiella ictaluri is the enterobacterium responsible for enteric septicemia of catfish, with channel cat fish being the most susceptible fish species among them to E. ictaluri .

Recently an attenuated O-antigen deficient E.ictaluri strain has been developed which was safe and provided high long lasting acquired immunity with immersion in 9-14 day old channel catfish.

Cold water disease or rainbow trout fry syndrome:-

• Flavobacterium psychrophilum has been known as the causative agent of bacterial cold water disease (BCWD).

• Recent vaccination experiment performed with young rainbow trout demonstrated that significant protection was achieved using oil-adjuvant (Intra peritoneal) vaccines.

Pseudomonadiasis:- (red spot disease)

o The Pseudo monas species recovered from disease fish. Pseudomonas anguillisetica is considered the significant pathogens for cultured fish.

o In recent research efforts production of aqueous and non-mineral oil- adjuvanted bacterins with proved to be effective in experiment trials in gilt head sea bream and turbot.

Bacterial kidney disease:-

o BKD caused by the gram-positive diplobacillus (Renibacterium salmoninarum) is a chronic systemic disease of salmonids which causes mortality in cultured fish in fresh and marine environment.

o Recently a commercial aqueous live vaccine developed by Novartis S.A has been licensed under the name of ‘Renogen’ for BKD prevention.

Viral vaccines

• Inactivated vaccines are used against infectious pancreatic

necrosis (IPN), infectious salmon anaemia (ISA) and pancreas

disease (PD) .

• A DNA vaccine against infectious haematopoietic necrosis (IHN)

is produced in in Canada. The vaccine gives acceptable protection.

• Research on DNA-vaccines for several diseases (IPN, VHS, koi

herpes virus-infection, spring viraemia in carp)

Potential benefits of vaccines Increased appetite and growth in vaccinated fish compared to non-vaccinated fish is

more because of the better food conversion rates in vaccinated fish.

Potential of growing vaccinated fish at higher densities because disease is not a limiting factor in the population.

Immunization of pre-spawning females may have potential as a means of protecting fish against pathogens which affect the early life stages , such as Flavabacterium psychrophilum, Edwardisiella ictaluri.

Reduction of drug use and therefore, the no appearance of bacterial drug resistance, as well as drug residues in the final product.

Improvement of industry image for the sanitary quality of the fish produced, as well as from the environmental safety stand point of view.

THE FUTURE- As part of health management measures, vaccination can be

effective for disease control in future.

To achieve progress in fish vaccinology, an increase in the co-operation between basic and applied science (i.e., between the Immunologist, microbiologist and the vaccinologist ) is needed.

Early identification and characterization etiology and epidemiology of the diseases of causing agent.

Identification of the earliest time to vaccinate and available windows for vaccination (i.e. ontogeny of the immune system) .

Development of new non-mineral oil adjuvants lacking side effects.

Development of polyvalent vaccines and standardization of a vaccination calendar appropriate for each economically important fish species.

Improvement in oral immunity with biodegradable microparticle based vaccines to be used for booster vaccination.

Investigation of the mechanisms of immunoglobulin transfer from pre-spawning females to offspring as a useful way of protecting fish against pathogens which affect early life stages.

Risk associated

The primary risk associated with vaccines, especially vaccines that utilize live organisms and vaccine itself may causes illness.

Vaccine may behave as a super antigen and over stimulate the immune system.

Some individuals may have an allergic reaction to the vaccine.

poor delivery technique may cause stresses which can result tissue damage, necrosis, infection or internal organ damage and death.

Decrease in growth caused by side effects such as those produced by some adjuvant vaccines.

Fish are weakened by improper handling or rearing practices.

Conclusion

Aquaculture continues to expand, disease problems will increase. Therefore, disease research and the implementation of new disease control concepts are important to maintain sustainability.

The development of an effective vaccine is a complex process. One of the prerequisites understanding of basic epidemiology of diseases and the immune system of the target species is required.

The importance of disease control is increasingly recognized by both farmers and governments due to the significant economic losses caused by diseases and international pressure on the use of chemicals and antibiotics.

A number of vaccines have been in used by the salmonid industry for decades, however, commercial vaccine development for other aquaculture sectors, including warm water fish, is still quite limited.

Currently, vaccines are available for some economically important bacterial and viral diseases but vaccines for protection against parasitic and fungal diseases have not yet been developed.

For the future of the fish farming industry it is also important that vaccination contributes to a sustainable biological production with negligible consumption of antibiotics.

Thus, increased resources have been allocated for disease research. In turn, to improved information on diagnostic techniques, infectious diseases and standardization of the culture practices will assist the development of vaccines in the future.

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