6.2 Biosecurity Plan

The wide diversity of farmed aquatic animal species, the variation in culture methods, environments, intensity of farming and interactions with wild aquatic animals and natural ecosystems make control of aquatic animal diseases challenging.

The concept of biosecurity planning, applied from farm to national level, provides an effective means of implementing disease control at multiple levels (Palic´ , Scarfe and Walster, 2015). At the compartment 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). Implementation of effective biosecurity programmes requires an integrated approach encompassing epidemiology, pathobiology, clinical and laboratory diagnosis, diagnostic assay interpretation, biosecurity, disease transmission routes, risk analysis, critical control point assessment, auditing, certification and associated ethics and liability, producer goals, and government and trade regulations (Palic´ , Scarfe and Walster, 2015).
Sound epidemiological principles and a logical and sound science-based approach used in formulating a biosecurity plan include the following elements:
• Hazard identification and prioritization that involves all diseases that pose a threat to the country or to marketability of export products, and varies depending on the level of application (farm, national, international) (Oidtmann et al., 2011). Routes of introduction and pathways of spread (transport of live animals or animal products, spread via water or fomites) are identified (Oidtmann et al., 2011).
Where water connectivity occurs between farmed and wild animals, priority should focus on prevention.

In simple terms, the question of “What can go wrong?” needs to be addressed (Arthur et al., 2005).
• Risk assessment evaluates the chances of a pathogen carried by an aquatic animal commodity entering a zone or compartment and the chances that wild or farmed animals within the zone or compartment will be exposed to infection. It poses the question, “How likely is it to go wrong?” (Arthur et al., 2005).
• Critical control point evaluation and remediation defines the pathways by which critical infectious pathogens may enter a compartment and the measures that can be implemented to control and monitor them, including clinical evaluation and diagnostic testing (Scarfe et al., 2009).
• Risk mitigation defines correctable critical control points, including contingency plans that make provision for actions such as isolation, treatment and fallowing. “What can be done to prevent diseases getting in or escaping?” (Scarfe et al., 2009).
• Disease surveillance represents the systematic series of investigations of a given population of aquatic animals for the clinical detection of disease occurrence or for detecting the presence or absence of a pathogen within a specified compartment, zone or country and includes monitoring of existing health problems (OIE, 2016). Single surveys seldom provide sufficient evidence to prove absence of a disease. Surveillance therefore encompasses ongoing collection, collation and analysis of information related to animal health. A function of surveillance includes the timely dissemination of information to those that need to know (Corsin et al., 2009). Surveillance activities are usually performed to achieve one or more objectives (OIE, 2016; Corsin et al., 2009; Cameron, 2002):
• demonstrate absence of disease to facilitate international trade;
• provide an early warning system of incursion or emergence of disease;
• identify events that require official notification and action; and
• determine occurrence and distribution of endemic disease, and changes in incidence and prevalence, to provide information needed for domestic control programmes and for risk assessment by trading partners.
Surveillance can range from basic passive surveillance systems, relying on the reporting of unusual disease events, to comprehensive targeted programmes to demonstrate absence of a defined disease or infection (Cameron, 2002; OIE, 2016).
Passive surveillance systems depend on the ability to recognize and the willingness to report unusual events and require the ability to investigate and identify pathogens when such events are reported.
Mortality rates, growth rates, and other health and production benchmarks should be used to alert authorities of a disease outbreak. In countries with limited resources, a range of other information can be sourced for basic surveillance, including anecdotal information, farm records, private and government laboratory reports, certification records, research investigations and fishery stock assessments (Corsin et al., 2009). Active or targeted surveillance follows a structured surveillance design, targeting specified diseases or pathogens often with the purpose of demonstrating the disease status of a defined population (Corsin et al., 2009).
• Control measures designed to mitigate the impact of aquatic animal diseases may include containment, eradication, disinfection and fallowing procedures.
Control measures should be based on the ability to define epidemiological units. Well-defined subpopulations of aquatic animals can then be managed according to realistic outcomes. Contingency planning makes provisions for the control measures that need to be applied in case of disease outbreaks and are best documented from the animal health management and biosecurity plan at the farm level to national and regional biosecurity strategies. This requires an active commitment from all stakeholders, including farmers, industry leaders, the competent authority and policy makers, with due consideration to differing attitudes and beliefs among role players (Delabbio et al., 2005).
• Eradication of the disease may be possible by destroying the stock within an affected epidemiological unit or units, followed by fallowing, in cases where a disease incursion within a compartment or zone has occurred. Eradication and disinfection provide a method of managing the impact of an introduced disease with the possibility of reinstating a disease-free status where effective barriers exist between the farmed and natural environment, and the water supply can be secured. Where a water body in which aquatic animals are farmed is continuous with or connected to the natural aquatic ecosystem, surveillance and early warning critical control points can be used to reduce the economic impact of a disease outbreak by timeous destruction of stock and a period of fallowing followed by reintroduction of SPF stock. This concept has been applied with particular success in the aquaculture of shrimp in a number of countries, and has contributed significantly to a resurgence of sustainable growth in this industry (Lightner, 2011).
An important motivation for aquaculture industries to actively participate in national biosecurity programmes is the ability of a country to compensate for officially ordered destruction of diseased populations and the implementation of enforced fallowing periods (Håstein et al., 2008). In this way, Denmark was successful in eradicating viral haemorrhagic septicaemia (VHS), a highly contagious salmonid disease, from more than 400 endemically affected farms after 45 years of surveillance and stamping out (OIE, 2015). Similar successful eradication of acute incursions of VHS disease has been reported from Norway and the United Kingdom of Great Britain and Northern Ireland (OIE, 2015).
Nations have developed biosecurity strategies to differing levels. Countries such as Australia, Canada, the United States of America and some European countries have developed operational national biosecurity plans in response to several serious diseases (Mohan, Chinabut and Kanchanakhan, 2008). The Aquatic Veterinary Emergency Plan (AQUAVETPLAN) of Australia represents one such effective emergency preparedness and response plan. Many other countries are in the process of developing similar regional and national biosecurity strategies (Bondad-Reantaso, Lem and Subasinghe, 2009).