6.4. Disease control in AMAs

Disease outbreaks pose one of the most significant risks to the sustainability of aquaculture. There are many examples of how the introduction of a disease or diseases has brought large aquaculture industries to the verge of collapse with serious economic and socioeconomic consequences.

Biosecurity can be broadly described as a strategic and integrated approach that encompasses both policy and regulatory frameworks aimed at analysing and managing risks relevant to human, animal and plant life, and health, as well as associated environmental risks (FAO, 2007a; 2007b).
As such, it has direct relevance to the sustainability of aquaculture, protection of public health, the environment, and biodiversity.
In the context of aquatic animal health, the term biosecurity is used to describe the measures used to prevent the introduction of unwanted biological agents, particularly infectious pathogens, and to manage the adverse effects associated with contagious agents. It encompasses both farmed and wild aquatic animals; exotic, endemic and emerging diseases; and is applied from the farm to the ecosystem, and at the national and international levels (Scarfe et al., 2009). Farmers should be encouraged or possibly mandated to follow sound biosecurity practices that provide the framework for disease management on the farm and that are implemented through documented standard operating procedures.

At the farm level, the owner or operator is responsible for ensuring implementation of biosecurity. Auditing and certification of the efficacy of a biosecurity programme is provided by the attending veterinarian and competent government officer.
Biosecurity planning, applied from the farm to the national level, provides an effective means of implementing disease control at multiple levels and for preventing catastrophic disease events. At the zone, compartment or AMA level, the biosecurity plan provides an auditable process of management procedures that can be evaluated by hazard analysis and critical control point (HACCP) methodologies (Zepeda, Jones and Zagmutt, 2008). Control measures designed to mitigate the impact of aquatic animal diseases may include containment, eradication, disinfection and fallowing. Control measures should be based on the ability to define epidemiological units.
Depending on the infection pathway of an aquatic animal disease, the epidemiological unit may need to encompass the entire AMA, or a subpopulation within the AMA, for instance, one of a group of farm sites within an AMA. Well-defined subpopulations of aquatic animals can then be managed according to realistic outcomes. The identification and prioritization of hazards represents the first step justifying implementation of a biosecurity scheme. This is followed by assessment of the risk posed by these hazards and the evaluation of critical control points whereby the risk can be remediated. Establishment of appropriate measures against a defined hazard or disease, including appropriate contingency planning, allows the risk to be mitigated. A programme of disease surveillance is instituted for the AMA to monitor occurrence or absence of a disease. Where a hazard or disease is detected or has been introduced, eradication and disinfection provides a method of managing the impact of disease with the possibility of reinstating a disease-free status. One of the outcomes of a biosecurity scheme is audited thirdparty certification. In order for a third party to provide disease status assurances, transparent and credible written records must demonstrate the effectiveness of the biosecurity scheme in preventing, controlling and eradicating disease within an AMA.
The devastation of the Chilean salmon farming industry by the ISA disease in 2007 provides an example of how AMAs have been implemented in this country to help rehabilitate the farming of salmon and to create an environment conducive to the sustainable growth of the industry (Ibieta et al., 2011). Establishment of AMAs appropriate for aquaculture has been legislated in Chile through the so-called “neighbourhood system”. These areas represent suitable zones for aquaculture activities according to appropriate epidemiological, oceanographic, operational or geographic characteristics, and incorporate complementary environmental, sanitary and licencing regulations. Epidemiological, operational and logistical characteristics of the AMAs are aimed to address the ISA virus infection and control. These site regulations include movement of all aquaculture concessions to AMAs, limiting the life span of a concession to 25 years (renewable), and banning the movement of fish from and between sea sites. This limits the movement of broodstock from sea sites to freshwater facilities, as well as the temporary use of estuarine sites. Fish inputs, disease prophylaxis, therapeutic interventions, sanitary issues, harvesting and fallowing are coordinated among the farms within the AMAs (neighbourhoods).
The distance between neighbourhoods has been established at a minimum of 3 nautical miles (about 5.6 km), and aquaculture sites must be spaced out by at least 1.5 nautical miles (about 2.8 km) from each other and from marine protected areas (natural parks and reserves) (Ibieta et al., 2011).