Strategies for health management

Introduction Diseases are difficult to be completely removed from aquaculture, can be controlled and frequency of occurrence can be minimised As the disease in aquaculture is a result of interaction between host, pathogen and environment, controlling all the three factors become important Controlling the entry of obligate pathogen to the culture systems and reducing build up of opportunistic pathogens are also equally important

Strategies for controlling the disease Use of closed or semi-closed recycle system with increased water reuse. Construct reservoirs for storing water without directly taking from the sea. Minimise water exchange. Treat reservoir water (chlorine at the rate of 30 ppm calcium hypochlorite - 60% active ingredient) before use in the ponds Prevent entry of wild shrimps, crabs and fish in to the ponds.

Contd….. In case of a disease outbreak, disinfect contaminated water before discharge. Maintain good pond preparation by drying pond bottom and removing top layer of the sediment. Avoid over stocking. Maintain good water quality. Feed nutritionally balanced diet at the required quantity avoiding excess feed.

Selection of a species is one of the potential methods of disease control in penaeids. Selection of healthy larvae and avoiding contamination during culture. Disease avoidance by using specific pathogen free (SPF) stock. Specifically, quarantining the stocks that are imported or transferred over a wide geographic area has to be practised.

Molecular biotechnological techniques Play an important role in controlling the disease incidences by improving the effectiveness of screening and detection of pathogens, elucidation of pathogenicity, development of effective control and preventive measures, treatment of diseases

Vaccination the ideal prophylactic measure that can be undertaken for protecting the fish from any infectious disease. A number of formulations of fish vaccination are available and many of them are also commercially marketed. Details of vaccination have been dealt in the chapter on vaccination.

Immunostimulants Immunostimulant is a chemical, drug, stressor or action that elevates the non-specific defence mechanisms by increasing phagocytosis, leucocytic activity and macrophage and neutrophil migration or specific immune response. play a significant role in the management of fish health and disease control in aquaculture farms. reduce the immune suppressive effects of stress.

immunostimulants used in aquaculture glucans, lipopolysaccharides, chitin, chitosan, peptidoglycans, muramyldipeptides, polypeptides, levamisole, Vitamin C, Vitamin E etc.

Probiotics It is a live microbial feed supplements, which beneficially affects the host animal by improving its intestinal microbial balance. The probiotic microbes when administered through feed could pre-emptively colonise the gut and eliminate or minimize the pathogenic microbes through competitive exclusion process. Lactobacillus has been effectively used as probiotic in improving the general health and growth characteristics of fishes.

Bioremediators Improve water quality by nitrification, removal of toxic substances such as ammonia, hydrogen sulphide and nitrite from the culture systems. Efficiently recycle the waste material by decomposing the complex organic substances and generating nutrients in the form of simple inorganic compounds. gram-positive Bacillus spp. are generally more efficient in converting organic matter back to CO2 than are gram-negative bacteria. Other bacterial species of importance towards bioremediation are: Nitrobacter, Pseudomonas, Enterobacter, Cellulomonas, and Rhodopseudomonas spp.