Animal health surveillance terminology

Draft output from pre-ICAHS workshop 2011

Introduction

This document provides definitions of general animal health surveillance related terms and lists of characteristics that can be used to describe surveillance activities and attributes that can be used to evaluate these activities.  The aim of producing this summary of animal health surveillance terminology is to facilitate communication between those commissioning, designing and implementing surveillance activities so that these activities can be clearly described.  A clear description of surveillance activities is required to ensure that the most appropriate methods are chosen to achieve different surveillance objectives in different situations.

 

These definitions and lists have been developed based on the definitions used by others in both the public and animal health fields and in discussions at two international workshops held in August 2009¹ and May 2011.  The definitions developed at the recent pre-ICAHS surveillance terminology workshop in May 2011 have been modified to produce the definitions included in this document based on comments received from workshop participants and other conference attendees.

1. Definitions of general surveillance terms

 

1.1 Surveillance^a1,2,3

The systematic, ongoing or repeated, measurement, collection, collation, analysis, interpretation and timely dissemination of animal health related data, essential for describing hazard occurrence and for the planning, implementation, and evaluation of risk mitigation measures

1.2 Monitoring ⁴

The systematic, ongoing or repeated, measurement, collection, collation, analysis, interpretation and timely dissemination information of animal health related data without an associated pre-defined plan of action

1.3 Early warning surveillance ^b,1,5 (epidemiological watch⁶, epidemiovigilance)

Surveillance of animal health in defined populations in order to increase the likelihood that there will be timely detection of undefined (emerging) or unexpected (exotic or re-emerging) threats

1.4 Syndromic surveillance ^1,7,8,9

Surveillance that uses health-related data (clinical signs or other data) that may precede or substitute for formal diagnosis; this information may be used to indicate a sufficient probability of a change in the health of the population to deserve further investigation or to enable a timely assessment of the impact of health threats which may require action

Notes

a) Control programmes may provide information that is consistent with this definition of surveillance i.e. it is continuously collected, provides descriptive information and is linked with action.  Other activities which do not satisfy this definition (particularly surveys but also analytical studies) may provide information about the level or distribution of disease so may need to be considered together with surveillance activities in some circumstances but these are not considered to be surveillance activities.

 

b) Early warning surveillance was previously known as ‘scanning surveillance’ in the United Kingdom

1.5 Threat specific surveillance ^c,1,2

Surveillance that is focused on one or more well-defined diseases, infections or conditions

1.6 Risk^d-based surveillance¹⁰

Use of information about the probability and or the magnitude of the biological and economic consequence of health events to plan, design or interpret the results obtained from surveillance systems including any of the following three components

• Risk-based prioritisation – to determine which health events should be selected for surveillance
• Risk-based performance requirement – to determine how much surveillance is required for the selected events in the population of interest
• Risk-based sampling – to determine how sampling should be distributed between strata in the population of interest

1.6.1 Risk^d-based prioritisation (to determine which health events should be selected for surveillance)

Determining which health events should be selected for surveillance based on information about the probability and biologic or economic consequence of their occurrence

1.6.2 Risk^d-based performance requirement (to determine how much surveillance is required for the selected events in the population of interest)

Use of prior or additional information about the probability of health event occurrence or introduction to revise surveillance-derived conclusions about disease status, or to revise the surveillance intensity required to achieve the stated surveillance purpose.

1.6.3 Risk^d-based sampling (to determine how sampling should be distributed between strata in the population of interest)

Reducing the number of samples taken, and therefore the cost of surveillance, by preferentially sampling strata within the target population that are more likely to be infected, detected, become infected, transmit infection^e or cause other consequences (e.g large economic losses or trade restrictions).

 

1.7 Sentinel surveillance¹

The regular, repeated collection of information from selected sites or data providers (e.g. herds or animals) about the health of a specified population

1.8 Participatory disease surveillance

A set of flexible methods that enable communities to share their knowledge regarding disease events, risk, patterns, impact and control opportunities that can be used to investigate the occurrence of disease and to enhance the value of other forms of surveillance data

 

Notes

c) Threat specific surveillance has previously been called ‘targeted surveillance’ or ‘specific surveillance’

 

d) In all of these risk-based definitions risk is being used as it is used in the risk analysis field to include both the probability that an event occurs as well as the consequence of occurrence rather than in the more restricted sense used in epidemiology which refers only to the probability of occurrence.

 

e) The extent to which each of the probabilities listed should be considered in determining the risk-based sampling strategy will depend on the purpose of the surveillance activity.

2. Characteristics that could be used to describe surveillance activities

Table 1 lists the characteristics that can be used to describe surveillance activities. These characteristics are divided into five groups to indicate which aspect of the surveillance system they describe (the names of these groups are in bold font in the first row of the table).  The suggested options for each characteristic are summarised in this table and listed and defined in more detail in tables 2-6 of this document.  The characteristics in the shaded boxes are those that were considered to be most useful for describing surveillance activities by those attending the pre-ICAHS workshop in May 2011.

Table 1: Surveillance description characteristics (key characteristics in shaded boxes)

2.1 Aim of surveillance	2.2 Organisation	2.3 Population included	2.4 Disease of interest	2.5 Information management
Surveillance purpose  (early detection, demonstrate freedom, determine level and distribution, describe changes	Scope of surveillance activity  (component, system, network, program)	Geographical area included  (local, provincial, national, regional, international)	Disease focus      (threat specific, syndromic)	Origin of information    (active (proactive), passive (reactive), enhanced reactive)
Policy purpose  (limit outbreak, Inform trade, prioritisation, inform control)	Units of interest    (animal, farm, batch, village)	Species / breed	Name(s) of health event	Data collection method
Expected outcome	Stakeholders – owners and beneficiaries	Basis of risk-based sampling  (based on probability of introduction, infection, detection, transmission)	Disease epidemiology  (endemic, exotic, re-emerging, new (emerging))	Study design    (case reports, existing data, survey, continuous monitoring, sentinel, participatory)
Anticipated actions taken	Management – personnel and organisational structure	Sampling strategy  (census, random, systematic, convenience, haphazard, volunteer, event-based, social networking)	Disease present    (present, absent)	Case definition
	Relationship with control activity    (integrated, autonomous)	Population stream  (healthy live, healthy cull, sick live, sick cull)	Disease control stage    (investigation, implementation, confirmation)	Data provided by
	Basis of participation  (voluntary, mandatory)	Age	Disease zoonotic    (yes, no)	Location of data collection
	Year started	Livestock sector		Diagnosis made by
	Units examined per year	Other selection criteria		Data management method
	Associated legislation and regulations			Data analysis method
				Dissemination method

 

 

 

Tables 2-6 provide definitions and options for each of the description characteristics listed in

Table 1, those considered to be key characteristics are in the shaded boxes in these tables

Table 2: 2.1 Characteristics related to the aim of the surveillance activity

Characteristic	Options or examples
Surveillance purposef	Describes what type of information will be obtained about the occurrence of a health event using a particular surveillance activity  Early detection / warning of known (exotic or re-emerging) or unknown (emerging) disease Demonstrate freedom from disease or infection Describe the level and distribution of specified disease(s) Describe changes in the health of the population or changes that may threaten the health of the population, this may include changes in the population at risk, changes in the occurrence of health indicators or of specified diseases Detect cases to facilitate control
Policy purpose	Describes how surveillance information is used by policy makers to decide how best to support a healthy and sustainable food and farming industry in order to protect the livelihood of producers and other value chain stakeholders and contribute to national economic development.  The specific decisions that surveillance information can assist policy makers with are  Limit outbreak - whether additional control measures are required to limit the spread of an emerging or exotic disease outbreak Inform trade - whether to permit import or support export of animals or animal products based on the evidence about the prevalence and distribution of disease in the population and the risk of disease spread through the commodity being traded Prioritisation - how to prioritise surveillance and control measures for different health events based on their level of occurrence and impact on animal health and welfare, public health, trade and the wider economy Inform control - Whether the current control measures for particular diseases are effective or should be changed
Expected outcome	E.g. Improved health or reduced prevalence of specified disease
Anticipated actions taken	E.g. Culling of affected herds

Notes

f) There may be additional benefits which result from surveillance activities but these are not considered to be the primary purpose of the surveillance activity, these include hypothesis generation, identification of risk factors for disease, improved our understanding of the epidemiology of a disease e.g. following the emergence of a new disease, facilitating epidemiological and laboratory research

Table 3: 2.2 Characteristics related to the organisation of the surveillance activity

Characteristic	Options or examples
Scope of surveillance activity	Component11 – a single surveillance activity focussed on a single disease or condition in a specified population System or network6,11 – a range of surveillance able to produce data about the status of a particular disease or condition in a specified population (may have more than one component) Program – a range of surveillance activities able to produce data about the status of many diseases or conditions in a specified population
Unit of interest	E.g. animal, farm, batch, village
Stakeholders – owners and beneficiaries	Name of organisation(s) paying for the surveillance activity and identification of beneficiaries
Management	Name of organisation(s) and expertise of the personnel managing the surveillance activity and description of the organisational structure
Relationship with control activity6	Integrated Autonomous
Basis of participation	Voluntary Mandatory
Year started	Year surveillance activity initiated
Number of units examined / year	Units / year
Associated legislation and regulations	Any legislation or regulations which act as the basis for determining the requirement for surveillance and whether  there are any compensation arrangements

Table 4: 2.3 Characteristics related to population included in surveillance activity

Characteristic	Options or examples
Geographical area included	Local – a small area within a country (e.g. border post, surroundings of natural park) Provincial – one or several administrative units within a country (e.g. county, department) National – an entire country Regional – includes a small number of countries corresponding to a geographical or political entity International – includes a large number of countries generally in a number of continents
Species / breed	Species and breed included (indicate whether proxy)
Basis of risk-based sampling	Whether the sampling strategy is risk-based and if so whether the population included has been selected because it is more likely to:  be infected with the disease of interest; detected as infected with the disease of interest; become infected with the disease of interest; transmit the disease of interest to other units in the population
Sampling strategy (for selection of study population from target population)	Census Random Systematic (e.g. selected on certain days) Convenience Haphazard Volunteer Event-based (e.g. pre or post movement) Social networking
Population stream	Healthy live Healthy cull Sick live Sick cull
Age	E.g. Adult, youngstock
Livestock sector	E.g. Herd type, production type
Other selection criteria	E.g. member of industry body

Table 5: 2.4 Characteristics related to the disease of interest

Characteristic	Options or examples
Disease focus	Threat specific1,2 – focused on one or more well defined diseases or conditions Syndromic1,7,8,9 –  uses health-related data (clinical signs or other data) that may precede or substitute for formal diagnosis
Name(s) of health event	Name(s) of health event to be investigated
Disease epidemiology	Endemic – A disease that is known to be present in the population of interest – could be constantly present  or irregular or haphazard (sporadic) Exotic – A previously defined (known) condition that crosses political boundaries to occur in a country or region in which it is not currently recorded as present Re-emerging12 – A previously defined (known) condition that is currently either absent or present at a low level, in the population in a defined geographical area that re-appears or significantly increases in prevalence New 12 (emerging) – A previously undefined (unknown) conditions, not currently recorded as present, which may result from the evolution or change in an existing pathogen or parasite causing a change of strain, host range, vector, or increase in pathogenicity; or may be the occurrence of any other previously undefined condition
Disease present	Present Absent
Disease control stage13	Investigation – to detect or assess level of disease and identify risk factors Implementation – to control disease Confirmation – to confirm diseases status e.g. freedom from disease
Disease zoonotic	Yes No

Table 6: 2.5 Characteristics related to information management

Characteristic	Options or examples
Origin of information1,6	Active (proactive) – Investigator initiated collection of animal health related information through actions scheduled in advance.  Decisions about whether information is collected and what information should be collected from which animals is made by the investigator. Passive (reactive) – Observer initiated provision of animal health related information (e.g. voluntary notification of suspect cases of disease or reporting of clinical signs) or the use of existing data for surveillance.  Decisions about whether information is provided and what information is provided from which animals is made by the data provider. Enhanced reactive – Enhancing the value of the surveillance information collected using reactive methods (e.g. by actively encouraging producers to report certain types of disease, active follow up of suspect disease reports or integration of data from different sources).  This type of surveillance is particularly useful for the detection of emerging disease but can also contribute to other surveillance purposes (e.g. exotic disease detection).
Data collection method	E.g. Postal, focus group, telephone, visit, internet, participatory methods, workshops (for some options can be manual or electronic)
Study design	Case reporting (voluntary or mandatory) Existing data (remote sensing, veterinary surgeons, laboratories, farmers, drug sales, abattoirs, media) Survey Continuous monitoring Sentinel – The regular collection of information from selected sites (e.g. herds or animals) about the occurrence of infection, disease or the health of a specified population Participatory – A set of flexible methods that enable communities to share their knowledge regarding disease events, risk, patterns, impact and control opportunities that can be used to investigate the occurrence of disease and to enhance the value of other forms of surveillance data
Case definition	Risk factor Clinical signs or syndrome (including death) Indirect indicators (e.g. drug sales, production or performance information, abattoir submissions) Gross pathology Laboratory test for pathogens or toxins Laboratory test for host response (e.g. serology) Specific diagnosis (e.g. VIDA code)
Data provided by	E.g. Farmer, vet, laboratory staff, haulier
Location of data collection	E.g. Farm, village, household, abattoir, market, fallen stock collection site, watering point, laboratory, drug sales outlet, vet
Diagnosis made by	Who is responsible for making diagnosis
Data management method	How is data managed e.g. central relational database
Data analysis method	How is data analysed
Dissemination method	The methods used for disseminating surveillance information during and after the surveillance activities

3. Surveillance evaluation attributes

Table 7 lists the attributes that can be used to evaluate surveillance activities.  This list of evaluation attributes is largely based on the work carried out in an ongoing project to develop a generic framework for the evaluation of animal health surveillance systems¹⁴ and a recently developed evaluation framework for animal health surveillance¹⁵.  Many of the definitions of evaluation attributes used in both of these frameworks are based on those used in the existing frameworks for the evaluation of public health surveillance^3,7,16.  The evaluation attributes are listed below in groups to indicate which aspect of the surveillance system they evaluate (the names of these groups are in bold font in the first row of the table).  The relationship between these groups of attributes is summarised in Figure 1 and definitions of each attribute are provided in the tables in tables 8-15 in this document.

 

Table 7: Attributes that can be used to evaluate surveillance activities (key attributes in shaded boxes)

3.1 Support functions	3.2 System processes	3.3 System function	3.4 Inclusion & engagement	3.5 Data quality	3.6 Evidence quality	3.7 System performance
Organisation and management	Data collection	Stability and sustainability	Coverage	Completeness and correctness	Sensitivity	Cost
Training provision	Data management	Flexibility	Representati-veness	Historical data	Specificity	Impact
Performance monitoring and evaluation	Communication and dissemination	Simplicity	Acceptability and engagement		Timeliness	Efficiency
Resource availability	Laboratory management	Repeatability			Bias	Benefit
	Data analysis	Multiple utility (inclusion of  multiple threats)			Precision

 

 

Table 8: 3.1 Attributes aimed at evaluating the support functions

Attribute	Definition / description
Organisation and management15	An assessment of organisational structures including the existence of relevant, clearly defined objectives and the existence of steering and technical committees whose members are representative of the surveillance stakeholders.  The members of these committees should have appropriate expertise, clearly defined roles and responsibilities and should hold minuted meetings regularly to oversee the function of the system.
Training provision15	Provision of adequate initial and ongoing program of training for those implementing the surveillance system
Performance monitoring and evaluation15	Whether performance indicators are routinely used to monitor system performance and periodic external evaluations are used to assess the system outputs in relation to its objectives
Resource availability	An assessment of the financial and human resources available for implementing the surveillance activity including the expertise and capability of personnel

 

Table 9: 3.2 Attributes aimed at evaluating the system processes

Data collection14	The use of appropriate data sources and collection methods and the existence of a case definition, data collection protocol including an appropriate sampling strategy
Data management14	Appropriate use and documentation of data management systems for processing information, including data processing protocols, and effective use of data verification procedures and data storage and back-up procudures
Communication and dissemination14	An assessment of the methods used and ease of information exchange between people involved at all levels of the surveillance system (providers, analysers and users of surveillance data). Including an assessment of the information provided including the timeliness and types of outputs produced and an assessment of the efforts made to disseminate these outputs and to increase the awareness of data providers.
Laboratory management14	Testing carried out using appropriate methods with quality assurance scheme and timely and accurate production of results
Data analysis14	Appropriate methods used for analysis and interpretation of data

 

Table 10: 3.3 Attributes aimed at evaluating the system function

Stability and sustainibility14	Reliability (function without failure) and availability (operational when needed) and (sustainability) the robustness and ability of system to be ongoing in the long term.
Flexibility14	Ability to adapt to changing information needs or operating conditions with little additional time, personnel or allocated funds. Flexible systems can accommodate new health-related events, changes in case definitions or technology, and variations in funding or reporting sources
Simplicity1	Refers to the surveillance system structure, ease of operation and flow of data through the system.
Repeatability14	How consistently the study results can be reproduced over time.
Multiple utility14	Whether the system captures information about several diseases or conditions

Table 11: 3.4 Attributes aimed at evaluating inclusion and engagement

Attribute	Definition / description
Coverage14		The proportion of the population of interest that is included in the surveillance activity.
Representativeness1,14		Extent to which the features of the population of interest are reflected by the population included in the surveillance activity, these features may include herd size, production type, age, sex or geographical location.
Acceptability and engagement14		Willingness of persons and organisations to participate in the surveillance system, the degree to which each of these users are involved in the surveillance process. Could include an assessment of stakeholder awareness of the system and their understanding of it. Could also assess their beliefs about the benefits or adverse consequences of their participation in the system including the provision of compensation for the consequence of disease detection

 

Table 12: 3.5 Attributes aimed at evaluating the quality of the data collected

Attribute	Definition / description
Data completeness and correctness1,14		Proportion of data that was intended to be collected that actually was and the proportion of data entries that correctly reflect the true value of the data collected
Historical data14		Quality and accessibility of archived data.

 

Table13: 3.6 Attributes aimed at evaluating the quality of the evidence provided

Attribute	Definition / description
Sensitivity1,14		Sensitivity can be considered on two levels . Firstly at the case detection level it refers to the proportion of cases or other health-events detected by the surveillance system. Secondly it can refer to the probability that the surveillance system will detect an outbreak of disease or that disease will be detected if present at a certain level in the population
Specificity14		Proportion of true non-events correctly classified as such. The inverse of this is the false alarm rate.
Timeliness14		The time between any two defined steps in a surveillance system. For outbreak detection, timeliness refers to the time between exposure to the infectious agent and the initiation of interventions to control infection.
Bias14		The extent to which a prevalence estimate produced by the surveillance system deviates from the true prevalence value. Usually (if not always) refers to endemic diseases. Bias is reduced as representativeness is increased
Precision14		How closely defined a numerical estimate obtained in the study population is. A precise estimate has a narrow confidence interval. Precision is influenced by prevalence and surveillance system quality.

Table 14: 3.7 Attributes aimed at evaluating the performance of the system

Attribute	Definition / description
Cost14	List and quantify each of the resources required to operate the surveillance system. For example: time, personnel, financial input and equipment.
Impact14		A measure of the usefulness of the surveillance system. Should include details of actions taken as a result of the information provided by the surveillance system e.g., changes in protocols or behaviour and changes in occurrence of disease
Efficiency1		Whether the surveillance system produces the desired effect with minimum use of resources, the aim being to maximise the effectiveness of outcomes relative to cost.  This can be assessed using measures of  cost-effectiveness i.e. the ratio of measures of effectiveness of surveillance (time to detection, total cases of disease) to costs of surveillance cost-benefit i.e. the ratio of the costs avoided as a result of decisions made to implement control measures based on surveillance system outputs (e.g. losses due to production or trade or human disease) to costs of surveillance and control
Benefit14		Direct and indirect advantages produced by the surveillance system. Not limited to money, benefits might include any losses avoided due to information provided by the surveillance system: financial savings, better use of resources, improved animal production, improved public health, increased understanding about a disease, increased trade or improved ability to react in case of outbreak

 

 

 

References

1. Hoinville L, Ellis-Iversen J, Vink D, Watson E, Snow L and Gibbens J. (2009) Discussing the development and application of methods for effective surveillance in livestock populations: Report of a workshop held prior to the ISVEE conference, Durban, South Africa
2. OIE Terrestrial Animal Health Code 2010 http://www.oie.int/international-standard-setting/terrestrial-code/access-online/ (accessed 07/04/11)
3. German RR, Lee LM, Horan JM, Milstein RL, Pertowski CA, Waller MN. (2001) Updated guidelines for evaluating public health surveillance systems: recommendations from the Guidelines Working Group. MMWR Recomm Rep, 50:1-35
4. Doherr MG, Audige L. (2001) Monitoring and surveillance for rare health-related events: a review from the veterinary perspective.  Phil Trans R Soc Lond B 356 1097-06
5. Gibbens J, Lysons R, Smith L. (2003) Veterinary surveillance in the UK: Developing a system for prioritisation. ISVEE proceedings, Vina del Mar, Chile
6. Dufour B, Hendrikx P. (2009) Epidemiological surveillance in animal health. CIRAD, FAO, OIE, AEEMA.
   1. Buehler JW, Hopkins RS, Overhage JM, Sosin DM, Van Tong MPH (2004) Framework for evaluating public health surveillance systems for early outbreak detection. MMWR 53:1-11
7. CDC (2006) Annotated bibliography for syndromic surveillance.  Accessed at http://www.cdc.gov/ncphi/disss/nndss/syndromic.htm on 17 December 2009
8. Triple-S: Syndromic surveillance systems in Europe (web site http://www.syndromicsurveillance.eu/ accessed on 11 April 2011

10.  Stärk KDC, Regula G, Hernandez J, Knopf LEA, Fuchs K, Morris RS, Davies P: Concepts for Risk-Based Surveillance in the Field of Veterinary Medicine and Veterinary Public Health: Review of Current Approaches. Bmc Health Serv Res 2006, 6:20

11.  Martin RAJ, Cameron AR, Greiner M. (2007) Demonstrating freedom from disease using multiple complex data sources 1: A new methodology based on scenario trees. Preventive Veterinary Medicine 79:71-97.

12.  King LJ. (2005) Emerging and re-emerging zoonotic diseases: challenges and opportunities. Compendium of technical items presented to the international committee or to regional commissions of the OIE 1-29

13.  Häsler B (2009) Economic Assessment of surveillance programmes ISVEE Proceedings, Durban, South Africa

14. RVC/AHVLA Generic evaluation framework being developed in project R10: SE4302

15.  OASIS evaluation tool website www.survepi.org/oasis accessed on 5 January 2011

16.  HSCC (2004) Framework and tools for evaluating health surveillance systems.  Report prepared by Health Surveillance Coordinating Committee (HSCC), Population and Public Health Branch, Health Canada for Branch Executive Committee, Population and Public Health Branch Health Canada