Risk Analysis in Aquaculture

Workshop for OIE National Focal Points for Aquatic Animals,Byblos, Lebanon, 12–14 August 2013

Edgar BrunOIE Collaborating Centre on Epidemiology and Risk Assessment for Aquatic Animal Diseases

Atlantic Veterinary College, Canada

Outline

Definitions Why do risk analysis Basic principals Constraints

What is risk analysis

An objective, systematic, standardized and defensible method of assessing the likelihood of negative consequences occurring due to a proposed action or activity and the likely magnitude of those consequences

Or…a model building process aiming to identify, describe, manage and communicate a riska tool for science-based decision-making (manage alternatives) a tool for how to deal logically with uncertainty and incomplete knowledge

What is «risk»

Risk in a daily languagethe chance of something going wrong any hazardous entity likely to cause injury, damage, or loss

is subjective (relative to our mind and culture)

is “invented” to understand and cope with dangers and uncertainties of life

Risk in epidemiology

Risk is the probability that an event will occur with a (generally) unfavorable outcome, in a specified time interval

(Last, 2000)

Risk in Risk Analysis

means the likelihood of the occurrence and the likely magnitude of the biological and economic consequences of an adverse event or effect to animal or human health

Risk = probability x consequence

Aquatic Animal Health Code (2012)

Event tree/Biological pathway

A “dissection” of the “risk-question” into a graphic diagram (model) showing a step by step pathway of all physical and biological events required for the hazard to occur.

Each step (event) can be dedicated a likelihood of occurring

Exampel; The biological pathway

1. Smolts descending the home river (N) 2. Smolts infected when leaving home river 3. Smolts swimming towards a neighbouring river 4. Smolts swimming up a neighbouring river 5. Ascending smolts still infected when swimming up (n)

Estimate the risk of one or more salmon smolt deriving from a Gyrodactylus salaris infected watercourse, to ascend neighbouring rivers still carrying viable parasites

Photo TAMo

“Total uncertainty”

“Lack of certainty”  exists whenever your knowledge or understanding of an event, consequence, or likelihood is inadequate or incomplete.

Uncertainty ● due to limited knowledge● imprecise measurements● can be reduced

Variability● normal variation ● can be measured and explained● can not be reduced

Lack of differentiation may lead to inadequate or incompleteknowledge or understanding of the results

Uncertainties are described by distributions

Depicted in a xy-diagrams; x= any value for the variabley = probability for occurring

Describes the likelihood of a given outcome of a stochastic variable (a stochastic process)

Beta(2, 100)

Values in Thousandths

0

5

10

15

20

25

30

35

40

-10 0 10 20 30 40 50 60 70

>5.0% 5.0%90.0%3.53 46.11

0,01 0,0325 0,055 0,0775 0,1

90% ,0145 ,0955

Mean=5,500003E-02

0,000

0,010

0,020

0,030

0,040

0,050

0,060

Mean=5,500003E-02

0,01 0,0325 0,055 0,0775 0,1

Sensitivity analysis

Testing the relative importance of the different variables (steps) in the pathway

- how and to what extent the various variables and their related uncertainty in a model affects the final result

Why do we need to do risk analysis in aquaculture Risk to farmed aquatic animals

● Introduction of pathogens through import (OIE/WTO)

●Where to establish new sites●Awareness of hazards (new/most important) ● Identify populations/areas most at risk● Identify farms most likely to be infected●Welfare

Risk to the environment●Pathogen exchange between farmed and wild●Genetic impact of escapees● Invasion of non-naïve species●Pollution from aquaculture or to aquaculture

Why do we need to do risk analysis in aquaculture

Risk to humans●Food safety and public health (Codex)●Social risks

Socio-economic (employment) Reputation Welfare

FAO (2008): Understanding and applying risk analysis in aquaculture

Basic principals

Four basic components in risk analysis

Hazard identification Risk assessment Risk management Risk communication

Hazard identification

The process of identifying which hazard(s) that could potentially produce which adverse consequences

● close collaboration with risk assessors and mangers for a precise definition of the task to be assessed (face to face meetings)

Hazard identification (characterization)

What do we know about the disease●Agent characteristics, clinics, treatment,

transmission etc. Diagnostic tests Distribution in exporting country Any surveillance in exporting country How sure are we of the situation in our own

country/farm

Risk assessment

the process of evaluating ● the likelihood that a defined hazard will be introduced, established, and spread● estimating the biological and economic consequences

Risk assessment (4 steps)

1. Release assessment – determine the likelihood that a hazard will be introduced (transferred) through a planned action (e.g. with a consignment)

2. Exposure assessment –determine the likelihood that a transferred hazard will be able to establish (spread) in its new environment

For release and exposure we need a pathway

1. Smolts descending the home river (N) 2. Smolts infected when leaving home river 3. Smolts swimming towards a neighbouring river 4. Smolts swimming up a neighbouring river 5. Ascending smolts still infected when swimming up (n)

6. Viable parasites able to infect susceptible species

Risk assessment

3. Consequence assessment – quantify the possible biological and economic damage the established hazard may cause

4. Risk estimation – integrating the estimation of the probability of release and exposure events with the results of the consequence assessment to produce an estimate of the overall risk of the event occurring.

Qualitative vs Quantitative RA

Qualitative RA (risk estimates in ”high”, “moderate” ”little”, ”negligible ”)● Often a first choice ● Quick, low requirement for data● Low level of precision , no measure for uncertainty

Quantitative RA (risk estimates in numbers)● Deterministic- model: using fixed (average) values

quicker, moderate quantitative data need low precision for uncertainty

● Probabilistic-model: using distributions for uncertainty and variability

good estimates for uncertainty, sensitivity analysis high demand for resources (time, money and competence)

Qualitative risk estimates

Rivers N Mean 95%CI Max p(0) River 1 13,000 0.1 0-1 5 91.9 % 65,000 0.5 0-4 11 76.5 % 130,000 1.0 0-7 17 69.2 % 200,000 1.5 0-10 25 65.7 %

River 2 13,000 0 0-0 0 100.00 % 65,000 0.00020-0 2 99.98 % 130,000 0.0003 0-0 2 99.97 % 200,000 0.00040-0 4 99.97 %  

Qualitative risk estimates

P(infected smolts ascending the river>0)=0.31

0.69

0.09 0.06 0.05 0.03 0.02 0.02 0.01 0.01 0.005 0.003 0.0040.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0 1 2 3 4 5 6 7 8 9 10 >10

Number of infected smolts

Pro

bab

ilit

y

Quantitative risk estimates (Risk matrix)

Risk management

The handling of the results from the risk assessment and implementing necessary means to reduce either the likelihood of realization (introduction and spreading) and/or the consequences of it

ensure a balance between a country's desire to minimise the likelihood or frequency of disease incursions and their consequences and its desire to import commodities and fulfil its obligations under international trade agreements (OIE).

Risk management

Deals with policy related to risk ● Acceptable level of risk

● Recognition of unacceptable risk and that some "risky" actions cannot be managed and therefore should not be permitted under any circumstance

● Application of the precautionary approach

A risk assessment may give more than one result Alternative risk management measures achieving

the required level of protection are equally acceptable

Benefits ?

Risk communication

A risk analysis strives for

objectivity, but contains elements of

subjectivity

transparency is essential.

Risk communication

A continuous open and transparent process where all stakeholders are consulted, results incl assumptions and uncertainty, and management measures communicated.

Should begin at the start of the risk analysis process and continue throughout

Peer review of the risk analysis is an essential component of risk communication for obtaining a scientific critique aimed at ensuring that the data, information, methods and assumptions are the best available

risk communication

Hazard identification

Risk assessment:-release-exposure-consequence-risk estimation

Risk management:-risk estimation-option evaluation-implementation-monitoring & review

What can go wrong?

How likely?How serious?

What can we do about it?

From the Aquatic Animal Health Code OIE has its focus on trade (IRA), but no a single

method of import risk assessment has proven applicable in all situations

The process needs to include an evaluation of the aquatic animal health service, zoning and

regionalization, and surveillance systems in place in the exporting country

Constraints in risk analysis

Technical● Resources (competence, time, money…)● Communication (internal/external)

Scientific● Definition of the question● Data

Usefulness● Credibility (is the question answered, is the model

correct) Management

● How to handle lack of information● Competence to act

Communicative● Terminology● Transparency● Results

Assumptions – limitations imbedded in the model

Final remarks

International aquaculture has a number of biosecurity and physical concerns that pose risks and hazards to both its own development and management, and to the aquatic environment and the human society

RA in aquaculture should be used to assess both risk to society and environment and from society and environment to aquaculture

RA can be used to improved sustainability, profitability and public’s perception of the sector

Thank you for your attention