Aquaculture in India and Bangladesh is traditionally centred on semi-intensive carp polyculture in fertilised ponds. Recently, supply deficits, and rural and urban demand, have stimulated rapid growth of more intensive pond monoculture of exotic tilapias and Pangasius catfish. In all cases, intensification has resulted in increased disease losses associated with a range of pathogens. Similarly, in southern Bangladesh, attempts to intensify a shrimp export sector dominated by more than 250,000 smallholders have been constrained by disease outbreaks. In India semi-intensive and some intensive production was supported through introduction of exotic L. vannamei (in 2009). Finally, India and Bangladesh are amongst the few major shrimp growing countries that remain unaffected by the Early Mortality Syndrome shrimp pandemic (EMS of AHPND); thus there is an urgent need for further research on efficacious PHPs.
Antibiotic use for disease control and growth promotion is increasingly constrained by spread of antimicrobial resistant (AMR) pathogens, whilst detection of antibiotic (and other chemotherapeutic) residues in shrimps and fish can lead to sector-wide export bans. Within this context, PHPs have become an increasingly important method of disease control. Prophylactic health products include probiotics, live microbial feed supplements that beneficially affect the host by improving the intestinal microbial balance . Health and growth promoting effects of these and other novel complementary treatments (prebiotics, synbiotics, phytobiotics, functional dietary supplements, etc.) have rapidly become the focus for considerable research. Only one product, Lallemand’s ‘Bactocell’ has had its health and growth claims independently endorsed and authorised for use as an aquaculture feed additive in the EU by the European Food Safety Authority (EFSA). Elsewhere end-users must accept ‘self-claims’. There is a plethora of un-validated PHPs on the market purporting to promote health, stimulate immune vigour and protect fish and shellfish against infection. Few have been subject to large-scale random controlled trials (RCT) and there is poor regulation of the quality, efficacy, and marketing of these agents.