ADDITIONAL DEFINITIONS RELEVANT TO NATIONAL SURVEILLANCE PROGRAMMES

Term

Definition (in the sense of this Technical Consultation)

Appropriate level of protection
(ALOP)

Actions designed to reduce the risk of an event occurring that is considered to present a level of risk that is unacceptable economically, socially, or environmentally, to an importing country, region or zone within a country. The level of protection, and actions associated with its implementation, must be commensurate with the level of risk and scientifically justifiable.

Acceptable level of risk
(ALOR)

The level of protection deemed appropriate by a country in establishing a sanitary or phytosanitary measure to protect human, animal or plant life or health within its territory (modified from WTO-SPS Agreement).

Assay

A test designed to isolate or detect evidence of an infectious agent.

Biosecurity measures

Appropriate measures or procedures in place to manage the probability of a biological organism or agent spreading to an individual, population of ecosystem and the harm that may result. Biological organism in this context includes a recognized disease agent, a new or novel disease agent, a recognized pest species that causes economic damage, or a species that would cause ecological degradation, reduce biodiversity or other adverse environmental effects.

Buffer zone

Zone between a positive and negative zone that requires stringent surveillance to prevent disease spread to negative zones, or ensure accurate definition of positive zone area.

Carrier or Reservoir host

A species that can carry an infectious agent without clinical sign of infection or evidence of development or proliferation, and which can transmit that agent to produce infections in either the known susceptible species or other carrier species.

Clinical infection

An infection that causes a subjective change in condition that reduces health, ranging from subtle signs to fatality.

Data

Data from disease surveillance activities:

· Primary (raw) data is generally data where the precise source (farm, animal, etc.) is known.

· Secondary data refers to aggregated data, such as the prevalence of disease in a given sample/series of samples/population.

Data management

Management of data from disease surveillance activities (i.e. general or non-specific; and targeted or disease-specific) that contribute to databases upon which zones are established and maintained, in such as way as to meet regional, national and scientific scrutiny/verification, as required.

Diagnosis

· Presumptive - Suspicion of an infection that requires additional analysis to confirm or refute.

· Conclusive - Diagnosis of an infection that requires no further analysis. Also known as Confirmatory Diagnosis.

Epidemiology

· The study of the distribution and factors associated with disease establishment, levels and spread.

· The study of the distribution and determinants of health-related states and events in populations and the control of health problems, the study of epidemic disease (Online Medical Dictionary, http://cancerweb.ncl.ac.uk/omd/).

· The study of populations in order to determine the frequency and distribution of disease and measure risks.

Immunization

Enhancement of host defence capability by exposure or by administration of a vaccine preparation containing actual or substitute pathogen antigens.

Import risk analysis (IRA)

The process by which hazards associated with the movement of a particular commodity into a country are identified and mitigative options are assessed.
Risk analysis incorporates risk assessment to identify possible risk mitigation options for evaluation in the socio-economic as well as ecological/habitat context of importation. See also OIE definitions for Risk, Risk Assessment, Risk Management and Risk Communication.

Intensity

The number of infectious agents present per infected host within a sample, expressed as a mean number, or qualitative rating.

Introduction

· Active introduction of a species to waters outside their current geographic range.

· The human-assisted movement of an aquatic animal to an area outside its natural range (FAO/NACA 2001).

Koch-Henle’s postulate

Application of Koch’s postulates distinguishes a pathogenic from an adventitious microbe (Davis 1980). The criteria used are: (a) the organism is regularly found in the lesions of the disease; (b) it can be isolated in pure culture on artificial media; (c) inoculation of this culture produces a similar disease in experimental animals; and (d) the organism can be recovered from the lesions in these animals.

Monitoring

A systematic series of investigations of a given population of aquatic animals to detect changes in the prevalence and geographical distribution of disease, which may involve testing samples of a population.
Collection and analysis of information necessary to detect changes in prevalence and intensity of infection (FAO/NACA 2001).

Outbreak (Disease)

A short term epidemic or a series of clustered (time or space) disease events that are new cases of a disease occurring at a higher frequency than expected, or due to a “new” disease.

Pathogen

An agent capable of causing clinical changes in a susceptible host may or may not be infectious. In the sense of this report, all pathogens are infectious.
An infectious agent capable of causing disease (FAO/NACA 2001).

Risk estimation

The process of integrating the results of the release assessment, exposure assessment, and consequence assessment to produce overall measure of risks associated with the hazards identified at the outset (Arthur and Bondad-Reantaso 2003).

Resistance

The ability of an organism to prevent infection by being refractive (the agent never invades the host) or by having an immune/defence response that can detect and kill all the infectious agents entering the organism.

Sensitivity and specificity

The inherent characteristics of diagnostic test which must be taken into account when interpreting the results of that test. Sensitivity is the ability of the test to detect infections where present and is an important characteristic for screening for sub-clinical or carrier infections. Specificity is the ability of the test to distinguish between significant pathogens and closely related or morphologically similar pathogens of less/no significance.

Surveillance programme

A programme that incorporates General (Passive) and/or Targeted (Active) surveillance, and may incorporate monitoring activities, where the programme is aimed at control of a disease that is present in some areas/zones, but absent from others that contain susceptible populations.

Surveillance Types

· General (or passive) surveillance is the ongoing work, which maintains a continuous watch over the endemic disease profile of a population so that unexpected and/or unpredicted changes can be recognized. General surveillance includes all the routine disease investigation activities that may be used in a country. This is also known as scanning surveillance by Scudamore (2002).

· Targeted (or Active) surveillance collects information about a specific disease or condition so that its level in defined population can be measured, or its absence reliably substantiated. This includes surveys and sentinel systems.

Susceptible

An individual or species that is incapable of defending itself against infection by a given disease agent, or group of related disease agents.

Syndrome

· A collection of signs and epidemiological factors that often occur together, and can be used to identify a disease.

· A set of signs or a series of events occurring together that often point to a single disease or condition as the cause (Online Medical Dictionary, http://cancerweb.ncl.ac.uk/omd/).

Tolerance/Tolerant

An individual or species that is susceptible to infection, but is capable of suppressing the infection to sub-clinical levels. Tolerance is usually acquired by survival of an initial exposure to infection, or generically by inheritance from parent stock that survived infection.

Transfer

· Active transfer of stocks of a species to waters within their current geographic range.

· The movement of an aquatic animal to an area within or across political borders (international, state/provincial or regional boundaries) (FAO/NACA 2001).

Vertical transmission

· Transmission of an infectious agent from parents to offspring via intra-ovum infection (vertical transmission sensu stricto) or via contamination of gamete surfaces, zygotes or larvae.

· The prenatal transmission (i.e. passed from parent to egg); may be either inside the egg (intra-ovum) or through external exposure to pathogens from the parent generation (Bondad-Reantaso et al. 2001).