Alpharma Vetregard

- the natural progression in disease prevention

The success of modern aquaculture has been the direct result of good management, good nutrition and good disease control. Vaccination and treatment have been able to control many diseases that affect farmed fish. However, circumstances change and new diseases appear for which specific treatments may not be available. This coupled with consumer concerns over food safety and protection of the environment has meant that new strategies for disease control have to be developed.

Vetregard is a combination of natural products derived from the yeast (Saccharomyces cerevisiae) and the bacterium (Bifidobacterium thermophilum) that can be added to the feed making administration both simple and cost effective.

Composition
Vetregard is a blend of beta 1.3 and 1.6 glucan, mannan oligosaccharide and peptidoglycan.

The beta glucan and mannan oligosaccharide are derived from yeast which has been processed through autolysis and standard proprietary procedures to maximise the Beta 1.3 glucan content. Quality control through documented ISO 9000 requirements ensures consistency and quality between batches.

The peptidoglycan is derived from the bacterial cell wall and manufactured according to GMP standards, again ensuring batch to batch consistency.

Administration
Follow a 6-2-6 programme. In-use experience has shown that feeding Vetregard at a rate of 1kg per tonne of feed gives the optimum results. Feed Vetregard for 6 weeks, followed by 2 weeks of plain feed and then 6 weeks again with feed containing Vetregard. This cycle can be repeated as necessary. The 6-2-6 programme can be used continuously through the production cycle, or it can be targeted at times of known stress, such as vaccination, smolting and prior to times of anticipated disease challenge.

IMMUNOSTIMULANTS - scientific background

The non-specific immune system is responsible for initiating a rapid and general response to an invading disease organism. Once the animal‘s physical barriers, such as the skin and enzymes on mucous membranes have been overcome, phagocytic cells (e.g. macrophages and neutrophils) within the body tissues and fluids locate, engulf and destroy the invading organisms.

Peptidoglycans (Fig.1) and Beta glucans (Fig.2) have been shown to have non-specific immunostimulatory effects in several species including fish (Raa et al, 1992; Matsuo et al, 1993). Mannan oligosaccharides have been shown to directly interfere with the ability of pathogenic bacteria to attach to the host cell, thereby preventing initiation of infection.

Immunostimulants have been extensively studied in fish species both at whole animal and on a cellular level. The immunostimulants attach to specific receptors on the cell surface of phagocytes and lymphocytes. This activates the cell resulting in increased production of enzymes that can destroy pathogens, chemical messengers (interferon, interleukins and complement proteins) that stimulate other arms of the immune system and increased activity of ‘T‘ and ‘B‘ lymphocytes.

Mannan oligosaccharide acts by blocking the bacterial adhesion to specific receptors on target cells. This allows the removal of the bacteria and prevention of the initiation of the bacterial infection.

Figure 1 - Peptidoglycan structure

IMMUNOSTIMULANTS - in aquaculture

Comprehensive studies have been conducted into the effects of both beta 1.3 glucans and peptidoglycan on the non-specific immune response.

Salmonids and other fish species
Experimental challenges have shown high levels of resistance (approx. 50-80%) against vibriosis (V.anguillarum, V.salmonicida) in Atlantic salmon (Salmo salar) pre-smolts as well as some protection against the causative agent of Enteric red mouth disease, Yersinia ruckeri (Robertsen et al, 1990). Rainbow trout have also been found to have enhanced resistance against IHNV (infectious hematopoietic necrosis virus) three weeks following injection of beta glucans.

At the cellular level, effects in salmonids have shown increased proliferation and activation of immune cells. Research has demonstrated that there are specific receptors for these immunostimulants on the surface of host cells. Beta glucan included into feed, has been shown to enhance resistance of pre-smolt Atlantic salmon to A.salmonicida (Jones, M 1992 personal communication) and V.anguillarum (Raa et al, 1992)

Recent work has demonstrated that peptidoglycan elevates the antibody level against Renibacterium salmoniarum in Atlantic salmon (Sorum et al, 1998). Protection has also been demonstrated in Rainbow trout and Chinook salmon. Similarly, improved resistance to infections caused by A.hydrophila, E.tarda and E.serillocida have been shown in African and Channel catfish and Yellow tail.

Alpharma�s collaborative research into the effects of immunostimulants on PKD (proliferative kidney disease) has shown some interesting preliminary findings. The studies show that addition of immunostimulants delay the initial infection of PKX parasites.

Crustacea
Crustacea lack the conventional immune system found in mammals and fish. However, they possess a non specific immune response system that includes agglutinins, killing factors, lysins, preciptins and clotting agents. These have all been associated with the removal of invading organisms, phagocytosis or haemocyte encapsulation.

Post larval Tiger shrimps showed enhanced growth and resistance to Vibrio vulnificus for eighteen days following the administration of beta glucan (Sung et al, 1994).

Kuboya et al, 1996 showed that feeding peptidoglycan to Tiger shrimps (Penaeus monodon) for forty days resulted in 100% survival when challenged with Baculovirus (RJ-PJ). Only 30% of the controls survived.

Figure 2 - Glucan structure

THE BENEFITS - of Vetregard in disease control

Vetregard has an important role as an aid to promoting health in conjunction with the strategic use of veterinary medicines and good nutrition.

Immunostimulants are

· Particularly suitable for boosting immature immune systems ·
· Effective against a number of opportunistic pathogens ·
· Useful at times of known stress such as transportation and vaccination ·
· Enhances immune response to conventional vaccines ·
· Safe and non-toxic - no risk of overdose ·
· No resistance problems ·
· Environmentally friendly, fully biodegradable ·

Vetregard contains beta glucan and peptidoglycan which are recognised as natural immunostimulants that can activate the non-specific immune system, helping the body to help itself.

1. Kuboya, K. et al, (1996). Effects of peptidoglycan on biphylactic ability of Penaeus japonicus. Zen-Noh product literature.

2. Matsuo, K and Miyazono, I. (1993) The influence of long-term administration of peptidoglycan on disease resistance and growth of juvenile rainbow trout. Nippon Suisan Gakkaishi 59, 1377-1379.

3. Raa, R et al. (1992) The use of immunostimulants to increase resistance of aquatic organisms to microbial infections. In Diseases in Asian Aquaculture 1 (Edited I.M.Shariff, R.P.Subsinghe and J.R.Arthur), Asian Fisheries Society, Manilla, Phillipines.

4. Robertsen, B et al, (1990). Beta glucans as immunostimulants in fish. In Modulators of Fish Immune Responses VI, Vol 1, Chapter 8.

5. Sung, H. et al, (1994). Vibriosis resistance induced by glucan treatment in Tiger shrimp (Penaeus monodon), Fish Pathology, 29 (1), 11-17.References

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