The fundamental basis for any decision to undertake surveillance under complex aquatic conditions is a clear understanding of the objective of such surveillance. The Expert Consultation (herein referred to as the Consultation) agreed that the primary purpose of aquatic animal disease surveillance is to provide cost-effective information for assessing and managing risks associated with:
protection of wild and cultured aquatic resources and their ecosystems from preventable disease threats;
trade in aquatic animals and products (intra- and international);
animal production efficiency;
This is consistent with international perceptions of what disease surveillance is meant to achieve in both terrestrial (OIE 2003a) and aquatic (OIE 2003b) production systems.
The objectives which define surveillance for aquatic animal diseases are:
rapid detection of new and exotic infectious diseases in wild and cultured aquatic animals;
provision of evidence of freedom from diseases relevant to domestic and international movement of aquatic animals and products;
accurate description of the distribution and occurrence of diseases relevant to disease control and domestic and international movement of aquatic animals and products;
assessment of control or eradication success for selected diseases and pathogens.
The Consultation also agreed that, although many types of surveillance exist, for the purpose of these guidelines and recommendations, only two are appropriate. The definitions for these are modified from Scudamore (2002):
General surveillance is an ongoing investigation or observation of the endemic disease profile of a population, so that unexpected and/or unpredicted changes can be quickly recognized. General surveillance includes all the routine disease investigation activities that may be used in a country which could detect the disease of concern if present. This is also known as passive surveillance or scanning surveillance by Scudamore (2002).
Targeted surveillance collects information about a specific disease or condition so that its presence in a defined population can be measured, or its absence reliably substantiated.
Fundamental principles are provided throughout this document to assist the design of scientifically sound surveillance programmes. However, users of the document must apply these with a clear understanding that there are no fixed rules or recipe book guidelines. General principles will always have to be adapted to fit the human and ecological factors faced within any given situation in order to establish and maintain effective zones.
The Consultation, organized by the Food and Agriculture Organization of the United Nations (FAO), the Federal Department of Fisheries and Oceans Canada (DFO Canada) and the World Organisation for Animal Health (OIE) to address such questions was held in October 2002 at the FAO Headquarters in Rome, Italy. Twenty-three participants were invited with expertise spanning global aspects of aquatic animal health management. Their input was aimed at providing recommendations for surveillance and zonation that will be useful for designing national programmes to reduce the risks of diseases arising from live transfers of aquatic animals. The recommendations and guidelines are not intended for use as international trade standards (the remit of the WTO and OIE), but extends to a broader application aimed principally at aquatic food security and encompassing protection from high risk trade as well as surveillance to protect against impacts from endemic diseases.
Five working documents prepared by selected experts provided the basis for discussion and development of recommendations during the Expert Consultation. Four working documents addressed technical issues related to: (a) freshwater finfish; (b) marine and diadromous finfish; (c) crustaceans; and (d) molluscs. Capacity building, information access and technical requirements for developing countries wishing to implement aquatic animal disease surveillance and zonation formed a fifth, non-technical, discussion document.
The development of the guidelines and recommendations outlined in this document were based on a set of seven general Guiding Principles, along with a set of scientific principles, encompassing surveillance to establish and maintain zones as applied to animals in general and specifically for application to finfish, crustaceans and molluscs.
Zonation is the process of delineating infected and uninfected populations within a country or group of countries. Infected zone and uninfected zone usually applies to specific diseases, except on the rare occasion where a range of different diseases share common epidemiological characteristics or can be detected using common diagnostic (non-disease-specific) techniques. An uninfected zone can be established within a country using the health status of a susceptible host species for a specific disease within a particular geographic or hydrographic area. Zoning is particularly relevant to controlling aquatic animal diseases, since these do not readily respond to disease control measures used for isolation and containment in land-based facilities or for terrestrial animals.