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particular animal are identified, the paths and likelihood of introduction and establishment are described,consequences are defined and management options are assessed. The results of these analyses arecommunicated to the Competent Authority and stakeholders (Importer/exporter). Typical risk analysis processinvolves four components: hazard identification, risk assessment, risk management and risk communication.Import decisions based on scientific risk analysis will minimize the risk of introducing exotic pathogens to thecountry.Zoning:Zoning is a program for delineating areas within countries on the basis of aquatic animal disease status. Theadvantage of zoning is that it allows for part of a nation’s territory to be identified as free of a particular disease,rather than having to demonstrate that the entire country is free. In the past, outbreaks of disease could impact ontrade from the entire country, but by zoning, restrictions may only apply to animals and products from the infectedarea. Zoning is particularly helpful for diseases where eradication is not a feasible option.Bio-security at farm levelBiosecurity refers to approaches taken to prevent, control and eradicate serious diseases of concern to thecultured species. Principles of biosecurity are normally considered for only dangerous pathogens. For any diseaseto occur, the pathogen should be able to gain entry into the culture system, through air, water, or land. Biosecuritymeasures implemented at the farm level should have the broad objective of preventing the entry, establishment,proliferation and spread of dangerous pathogens. Farm level biosecurity can be broadly defined as sets ofstandard practice that will reduce the probability of pathogen introduction to the culture system, its amplification inthe culture environment and cultured host leading to disease outbreak and subsequent spread. To achieve, foolproof bio-security, it is necessary to understand all the routes by which the pathogen gains entry into culture unitsand the farm level component causes (risk factors) which favor its amplification to levels sufficient to causedisease outbreaks. In the case of serious pathogen disease outbreak (e.g. WSSV), damage control should be theonly post-outbreak goal. Isolation of affected farm, removal of hosts, effective disinfection programs, early warningsystems and co-operation of processors in avoiding contamination would help to contain the spread of thepathogen.Good biosecurity programs with external and internal barriers are vital to maintaining healthy animals and toreducing the risk of acquiring diseases in a farm. External barriers prevent the spread of pathogens onto and off afarm. Internal barriers prevent the spread of the pathogen within a farm. Adoption and implementation of principlesof good bio-security program can minimise the probability of pathogen introduction considerably. Pathogens,which are endemic and well established in diverse hosts find their way into farms, despite the best bio-securitymeasures. It is well known that mere presence of pathogen (necessary cause) alone will not lead to diseaseoutbreaks. Identification of farm level component causes (risk factors) through epidemiological studies and theireffective management would help prevent disease outbreaks despite the presence of the necessary cause.Application of principles of biosecurity will depend on the types of culture systems. It may be easy to adopt andimplement in land based systems which are under cover and in closed aquaculture systems. The practicalities ofapplying principles of biosecurity in open farming systems may be difficult and needs to be viewed from a differentperspective. Identification and quantification of relative risks associated with each possible route of pathogen entryinto the farms through epidemiological studies help to target resources only to the main risks, to make biosecuritymeasures cost effective at the farm level.Bio-security principles for preventing pathogen entryPossible pathogen carriers include infected hosts (e.g. seed, broodstock, vectors, intermediate hosts, reservoirhosts), non-host biological carriers (e.g. birds, dogs, insects, other predators, human beings) and fomites (e.g.20