Laboratory Division

15 Apr Aquaculture is a door to end world hunger

Fish vaccination is the key to open it

Aquaculture all over the world has suffered the Covid-19 pandemic a lot, nevertheless it has also shown its adaptive capacity to react. It will always find its way to cope with the new and constantly evolving constraints and its potential to provide increased livelihood opportunities is not at risk. In fact, aquaculture is widely regarded as one of the most important weapons to fight against world hunger and malnutrition.

To achieve this potential, aquaculture will need to provide both a wide range of high-value products for international markets and a copious supply of low-cost fish for domestic consumption. The fast growth of this sector continues to generate new challenges. Diseases are still a main issue, because they may generate big losses on rural communities, resulting in a lack of investor confidence.

The development of commercial aquaculture has made it necessary for farmers to use veterinary medicines to treat disease outbreaks due to pathogens. They are, however facing a general perception, worldwide, that veterinary antimicrobial agents have been imprudently used in this industry.

Authorities should obviously promote the sustainability of aquaculture production and protect public health. In parallel, ensuring the judicious use of medicines remains the responsibility all animal professionals and fish farmers must share.

Favouring preventative measures and vaccine use to reduce exposure to pathogens is an important goal in animal health science. The concern about antibiotic and antimicrobial resistance is well known and documented. The main worry for animal health is treatment failure, whereas the possible presence of residues in food products is an alarming issue for humans. The development of bacteria resistance associated with human disease is also worrying. Antimicrobial resistance refers to microorganisms that have acquired resistance to antibiotics. This phenomenon can occur naturally as microorganisms adapt to their environment; aggravation is observed when inappropriate and excessive dosages of antibiotics are prescribed.

In fish farming, several strategies apply to reduce antimicrobial resistance. These include usage of clean facilities, use of immunostimulants to enhance innate immunity, inclusion of probiotics in feeds, and of course vaccination. Of these, vaccines are the most important weapon against fish infections, being the last barrier pathogens will find before causing a disease outbreak.

The emergence of vaccines has greatly reduced the dependence on antimicrobial agents. Vaccination benefits us all, as it protects animal health and welfare, the livelihoods of those who work with livestock, as well as food security. The development of some aquaculture sectors, such as the salmon industry in Norway (where, by 1994, fish farmers across the country had switched from antibiotics to vaccination), has shown the great potential vaccines have towards reducing reliance on veterinary medicines.

Recent trials have been performed to test protection against vibriosis anguillarum, involving various European sea bass groups, even under adverse temperature conditions. They have proven that the unvaccinated fish groups reached a mortality rate of 95%, while all fish properly vaccinated by intraperitoneal injection 42 day earlier survived, meaning that vaccination was nearby 100% successful.

Those experiences confirm that vaccination is not only essential to drastically reduce antimicrobial resistance. It is also the best method to increase survival rate and profitability. Among the several vaccination methods that are available, vaccination by manual injection (intraperitoneal or intramuscular), has proven preferable where species allow.

In fact, injection is highly efficient in generating both humoral (antibody) and cellular cytotoxic responses. Immersion vaccination's major disadvantages is the large amount of vaccine required and the lower protection in immunity level and duration. The protection generated by oral vaccination is generally weak and of short duration; in addition, it requires all individuals to be fed. Vaccination by automatic injection requires highly sophisticated and expensive machines. Nevertheless, other factors including size of fish and type of pathogen are constraints when choosing the best suitable application method.

Fish have a functional immune system similar to that of mammals (innate & adaptive), major differences with other vertebrates being that their metabolism and immune response is temperature dependent. Therefore, temperature is another important aspect of the vaccination strategy.

In case of hand injection vaccination, fish are transported in pipes from the rearing tanks to an anaesthetic bath, tranquilized animals are then injected by skilled vaccination teams.

The dosage of vaccine may vary (in most cases 0.05 to 0.2 mL for specimen weighing 15 - 80 grams); it is important to follow the proper posology as recommended by the manufacturer or ichthiologists involved. Obviously, the syringe capacity must be in adequation with the administered injectable volume.

The Socorex® ultra 1810 micro-range tube feeding syringe line delivers highly precise doses, setting new standards in micro-volume injections and breaking down volume barriers. The self-refilling automatic injectors are suitable for use with most vaccines and medications in volume ranges within 0.02 mL and 0.5 mL.

When choosing the proper instrument, it is important to identify the suitable volume/plunger stroke combination, in order to optimize operator working comfort. Volume is easily set and locked by means of a micrometric screw for a safe, high dose-to-dose reproducibility, even with very small volumes. Intended for long lasting use, the Socorex® ultra series are extremely robust, yet light in weight. With no comparison with plastic semi-consumable instruments found in the market, their ergonomy, user friendly handle and smooth plunger movement, ensure fatigue-free operation at rates of up to 1,000 injections per hour.

Correct needle size must be considered, with 23 - 25-gauge models being most commonly used for injecting fish, while standard length is often ranging 3mm to 5mm – considering 1mm should penetrate the stomach wall. Proper handling position is crucial, as wrong shot sites or needle direction may pierce the swim bladder, or injure the user, with its known consequences. The Socorex® FishGuide™ accessory reduces such risks and facilitates immobilizing fish during vaccination. Adaptable over 360°, the rotating device is easy to position for smooth, safe and stressless operation. The water-proof Abacus™ shot-counter constitutes an ideal addition to manual vaccination. Firmly mounted on the injector, the Abacus™ grandly facilitates the monitoring of delivered shots figures and therefore the number of treated specimen.

In summary, producing healthy fish-farmed proteins requires a global approach, not only with regard to quality infrastructures and well-trained personnel, but also placing the latest pharmaceutical technologies and state-of-the-art instrumentation and consumables on the fore-front. Keeping the health and safety of humans and animals in mind, with no compromise to environmental commitments, should be the key to reach global sustainability goals.

 

Last modified on Thursday, 15 April 2021 07:59