Evaluating Costs and Benefits of Prophylactic Health Products and Novel Alternatives on Smallholder Aquaculture Farmers In Asia and Africa (IMAQulate)

Rapidly growing demand for seafood products for domestic and export markets is driving intensification of aquaculture sectors dominated by small-holders in much of Asia. Ensuring effective health management has become the single most important challenge for sustainable intensification of the smallholder sector just as restrictions on antibiotic use are being imposed. Farmers are increasingly dependent on a proliferating range of prophylactic products (including pre and probiotics), often of uncertain provenance & efficacy. Furthermore, the emergent markets for these products lack appropriate regulatory frameworks and the economic burden of unjustified claims is likely to fall most heavily on small-holders. An independent cost-benefit assessment of the efficacy, costs and benefits of such products is urgently required. Working across a range of major commodity farmed species and system types, the project will also assess the potential for novel low-cost alternatives to contribute to improved animal health and profitability of intensified smallholder operations.

Probiotics alter the intestinal microbiome, or the microbiological composition of pond water and sediments. Modifications in the composition of the microbiome, alter the immune response and change a host's ability to resist infection. The microbiome educates the immune system; inducing tolerance to luminal contents and by stimulating and enhancing local and systemic immune responses for the detection of incoming pathogens. In addition, the microbiome promotes gut physiological functions such as maintenance of mucosal barrier integrity, competitive exclusion of gut pathogens, organisation of gut lymphoid tissue, modulation of epithelial cell differentiation, absorption of nutrients and induction of Ig+ cells, granulocytes and T cells. A balanced microbiota is essential for health and growth in farmed species; perturbation of non-pathogenic microbes in the existing microbiome alters production. Probiotics have been found to increase lymphoid tissue of fish interacting with the microbiome in a complex response involving the production and regulation of cytokines and effector and regulatory T cells. For example, different probiotics have been found to have beneficial effects in Tilapia with increased serum complement activity, enhanced phagocytosis and bacterial killing associated with an increase in peripheral inflammatory cytokines IL-1 and TNFa [. Several other studies report probiotic Bacillus sp. to increase shrimp survival and notably in a mix with Vibrio sp to be protective against V.harveyi and the white spot virus (WSSV). Vaccines exploit the adaptive component of the immune system but many do not provide full protection. Vaccines are also inappropriate for shellfish, which rely on innate mechanisms. Scope therefore exists to target the innate component for both finfish and shellfish, non-specifically, to infection by acting as a 'surveillance and rapid response' mechanism. Unlike the adaptive system it functions through all life stages.

The project aims (i) to improve profitability of intensifying smallholder farmers directly: through improved prophylactic health management capacity and indirectly through development of standardized assessment procedures and improved regulation of commercial PHPs (ii) to develop internal capacity to support future research on PHP efficacy, regulation and economic benefit.