NON-SPECIFIC IMMUNE STIMULANTS

Many compounds have been found to have non-specific immune stimulating properties in animals of which more than a dozen (Table 1) have been evaluated in fish and shrimp (11,12). The vast majority of these have only been tested under controlled conditions in the laboratory in fish and though a number of them do provide benefits, field tests will be the deciding factor in determining which ones find a niche in the market place. Only a few have been tested to determine if they impact viruses affecting shrimp, specifically WSSV.

This paper focuses on those that have been found to impact viruses, specifically the WSSV, in crustaceans. These compounds fall into several broad categories and most are the cell wall materials of bacteria or fungi. The evaluation of these compounds in the field is plagued by several serious technical problems, not the least of which is that there are rarely accurate diagnoses made of the cause of mortalities. Mortalities are often due to many factors and it is usually difficult to say that one thing was the cause of a problem or that the use of a compound solved the problem.

Table 1. Compounds with purported immune stimulating properties in fish and/or shrimp

Laminarin	Curdlan	Chitosan	Saponins
Barley Glucans	Scleroglucan	Beta 1-3 glucan	Herbal extracts
Lactoferrin	Zymosan	Dextran	Peptidoglycans
Levamisole	Schizophyllan	Lentinan	MDP
Lipopolysaccharides	Inulin	Krestin

These compounds are typically tested in two different manners, one is by exposing animals to the substance in a water suspension and the other is by feeding it. Water borne exposures require determination of the length of exposure and concentration. Oral application requires the same approach however it has the added variable of the digestibility of the material being used. A classic example of this is the class of sugars known as the beta 1,3 glucans. It has been known for some years that these molecules are digested by crustaceans (13,14,15) yet they are being sold for use in the feed. Given the ease with which they are digested and the apparent importance of their structural integrity on their biological activity, it makes little sense to feed them to shrimp.

Since the immune response of shrimp is non-specific in nature (16), it is highly likely that any substances with activity by immersion or orally in shrimp will have an impact against a broad range of pathogens. Any differences in activity may relate to the structure of the materials used as with the glucans and what component of the immune system they likely affect as well.

Anti-viral activity has been reported in shrimp for lipopolysaccharides (LPS) (17), peptidoglycans (PG) from several species, Bifidobacterium (18), Brevibacterium (19) and Bacillus (20) and glucans from Schizophyllan commune and Saccharomyces cereviseae (21). Additionally a compound with anti-enveloped virus activity (22), a sulfated polysaccharide, fucoidan, (23) has been reported to have anti-viral (WSSV) activity as well. Several studies have also reported anti-viral activities of various homeopathic herbs (24,25,26).

- From A Review of the Use of Non Specific Immune-Stimulants to Reduce the Impact of the WSSV.

Fifth Ecuadorian Aquaculture Conference

October 28-30, 1999

Mission

Specification

Testimonial - Takahasi

Testmonial - Itami

Non Specific Immunity

WSSV