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The Importance of Biosecurity Disinfection

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Biosecurity in aquaculture consists of practices that minimize the risk of introducing an infectious disease and spreading it to the animals at a facility and the risk that diseased animals or infectious agents will leave a facility and spread to other sites and to other susceptible species. These practices also reduce stress to the animals, thus making them less susceptible to disease. Over the past decade, a number of important disease outbreaks in both U.S. aquaculture (spring viremia of carp, koi herpesvirus) and wild fish populations (viral hemorrhagic septicemia type IVb) have increased the industry’s awareness of the importance of biosecurity. Examining specific points in production when pathogens (disease-causing parasites, bacteria, viruses and fungi) may be introduced or disease may develop will help producers develop precautionary measures. Good biosecurity minimizes the fishes’ exposure and susceptibility to pathogens, reduces economic losses from mortalities, and helps prevent mandatory depopulation. This publication provides an overview of major concepts in biosecurity for aquaculture. Although it concentrates primarily on finfish, the principles described also hold for other species groups. Because biosecurity management differs with the type of system, two additional publications will cover specifics for tank and recirculating systems (Part 2) and ponds (Part 3). Major Goals of Biosecurity Major biosecurity goals are: animal management—obtaining healthy stocks and optimizing their health and immunity through good husbandry pathogen management—preventing, reducing or eliminating pathogens people management—educating and managing staff and visitors The ease with which a specific pathogen can enter a facility, spread from one system to another, and cause disease depends on: the species, immune status, condition, life stage, and strain susceptibility of the cultured fish; major environmental factors such as water quality, water chemistry, and husbandry practices; characteristics of the pathogen, such as biology and life cycle, potential reservoirs (carriers, other animals), survival on inanimate objects (equipment), options for legal treatment(s), regulatory status (exotic vs. endemic disease, reportability, and federal, state and local laws); and workers’ understanding of biosecurity principles and compliance with biosecurity protocols. Animal and Population Management Obtaining healthy animals (eggs, fry, juveniles, broodstock) from a reputable supplier is critical. Work with a fish health professional to determine species-specific health parameters and diseases of concern. Before obtaining animals from an outside source, learn as much as you can about their health, including where they came from, whether they have had any disease issues, and whether they have had any health examinations, disease testing, or treatments. Some suppliers offer animals that have tested free of specific pathogens and these animals are preferable. If information about animal health is unavailable or unclear, fish should be tested shortly after they are received. Strains of some aquacultured species are known to be more resistant to specific diseases. Tracking the lineage/ genetics of your broodstock helps avoid inbreeding and ensure the production of healthy gametes and fry. Good husbandry is also important to biosecurity. Any environmental conditions or procedures that stress the fish or that may damage the skin, fins, gills or intestine will weaken their immune systems and make them much more susceptible to disease. Good water quality/chemistry, nutrition, and handling methods will go far toward preventing disease. Good preventive medical practices include quarantine, routine observation, vaccination, and the use of immunostimulants, probiotics, and diagnostics for disease management. Quarantine is one of the most important animal management and biosecurity measures. Quarantine is the procedure by which an individual or population is isolated, acclimated, observed and, if necessary, treated for specific diseases before its release onto the farm or for live market sale (e.g., for growout or for aquarium fish stores). The principles of quarantine apply for new fish coming into a facility, fish moving from one area or system to another within the facility, and resident fish that become diseased. Well-designed quarantine systems physically separate incoming fish from the rest of the farm. Water in quarantine systems also should be separate from that on the main farm, and discharges should be handled appropriately. Proper quarantine not only protects established populations from potential exposure to pathogens but also gives the new animals time to acclimate to water, feeds and management and to recover from handling and transport. Handling and transport have been shown to reduce disease resistance and recovery may take weeks. Fish in the general population that become sick may have to be isolated in tanks in the same system or room as their healthy counterparts; signs or other methods should be used to alert employees that the population is diseased. Major components of quarantine include all-in-allout stocking, isolation or separation, observation and diet adjustment, and sampling and treatment. All-in-all-out stocking. This involves bringing animals in as a group from only one original source population and maintaining them as a group throughout the quarantine period. It prevents exposure to other pathogens not currently in that population. Ideally, no new animals should be added to a group currently in quarantine. All-in-all-out quarantine may involve an entire facility, room or system. Isolation or separation. A group of animals in quarantine should be physically isolated from other quarantined populations and from the resident populations. Methods of isolation should be built into the facility and system design. If logistics prevent complete isolation, populations should at least be separated by tank or vat. Regardless of the level of isolation, appropriate sanitation and disinfection measures must be used to reduce cross-contamination between quarantined and established populations and between separate populations in quarantine. Observation and diet adjustment. Animals should be observed for normal and abnormal appearance and behaviors throughout the quarantine period so disease problems can be detected early. Loss of appetite, for example, is a very common, early sign of disease. Good nutrition will increase disease resistance and careful adjustment from the diet of origin to the on-farm diet will reduce problems from sudden changes. Sampling and treatment. Fish in quarantine should be sampled for specific diseases of concern at the beginning and end of the quarantine period and at any time that disease signs develop. Although complete necropsy evaluation of a number of specimens is best, limited sampling of more valuable specimens can be done without sacrificing the animals by examining small sections of skin, fin and gills for parasites and doing a blood culture for systemic bacterial infections. The results can then be used to improve quarantine methods and the use of drugs. Consult with a fish health professional to assist with this. Legal issues associated with drug usage should be considered before treatment.