The process of recovery, following a successful eradication of an emergency disease, involves verification and international acceptance of proof of national disease freedom. Rehabilitation of affected farming and fishing communities is also required to help rebuild socio-economic losses and re-establish lost markets.
The important objective with respect to regaining freedom from an exotic disease is to ensure that the causative agent, not just the clinical evidence of the disease, has been eradicated. There are many examples where intense eradication efforts have been stopped when the disease seems to have disappeared; however, small pockets of infectious agents remain that multiply to disease levels as soon as the host populations begin to build up again in numbers. Failure to completely remove the pathogen from the environment or production system, therefore, undermines the investment in expensive eradication programmes.
Disease control measures should diminish once the active disease outbreak has come under control and either stabilized or the pathogen is thought to have been eradicated. Emphasis shifts from mapping the disease spread towards targeted surveillance to detect any residual infection. If vaccination has been used, this should be stopped so that there is no masking of infection. If the disease and/or agent have not been eradicated, surveillance efforts shift from the infected zone to a defined buffer zone around the affected area. This should be subject to stringent controls and targeted surveillance to ensure that the disease remains contained within the delineated positive zone.
When it is believed that infection has truly been eradicated (a situation that is likely to occur only within confined growing conditions such as farm facilities), a series of verification programmes should be carried out. These are aimed at providing objective proof to areas with unaffected susceptible populations (trade partners or other areas within the country) that the affected population(s) has/have regained freedom from the disease agent. This will provide the foundation for export of the animals and/or their products to be restored to areas that are unaffected and have populations at risk from the disease. This may involve:
Reference should be made to the FAO publication on Surveillance and Zonation for Aquatic Animal Diseases (FAO, 2004) and the OIE's Aquatic Animal Health Code (OIE, 2004) for more guidance on acceptable methods and principles for declaring freedom from specific infectious diseases.
If a disease agent has been successfully eradicated from an area, there will be a need to repopulate with disease-free animals. There is little economic benefit in repopulating any area in which a disease has become established with naïve (disease-free) animals. In this case, rehabilitation must focus on alternative species, or on protecting survivors that may have a degree of disease tolerance. These animals can be invaluable as the progenitors for controlled breeding programmes for disease resistance.
Special support mechanisms and programmes can be considered to allow affected farmers and fishing communities to get back on their feet after an economically devastating disease outbreak. Providing full or partial compensation to fish farmers for their losses due to a disease epizootic or to government-mandated destruction of infected stocks is a political decision, based of a range of factors (usually prescribed in legislation). Responsible authorities should consider these issues when developing the legislative frameworks to support contingency planning. It should be noted that compensation is rarely considered for recurrent diseases, especially in open water. Restocking vulnerable species in waters where significant disease agents are known to occur should be given serious risk assessment consideration for the potential of a repeat disease outbreak, prior to stocking.
